1.
Epoxide
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An epoxide is a cyclic ether with a three-atom ring. This ring approximates an equilateral triangle, which makes it strained and they are produced on a large scale for many applications. In general, low molecular weight epoxides are colourless and nonpolar, a compound containing the epoxide functional group can be called an epoxy, epoxide, oxirane, and ethoxyline. Simple epoxides are often referred to as oxides, thus, the epoxide of ethylene is ethylene oxide. Many compounds have trivial names, ethylene oxide is called oxirane, some names emphasize the presence of the epoxide functional group, as in the compound 1, 2-epoxycycloheptane, which can also be called 1, 2-heptene oxide. A polymer formed from epoxide precursors is called an epoxy, the dominant epoxides industrially are ethylene oxide and propylene oxide, which are produced respectively on the scales of approximately 15 and 3 million tonnes/year. Other alkenes fail to react usefully, even propylene, many epoxides are generated by treating alkenes with peroxide-containing reagents, which donate a single oxygen atom. Outside of the scale, the main challenge with this approach is that typical peroxides are more valuable than the product epoxides. For this reason, this methodology is restricted to fine chemical applications, metal complexes are useful catalysts for these reactions. Typical peroxide reagents include hydrogen peroxide, peroxycarboxylic acids, and alkyl hydroperoxides, in specialized applications, other peroxide-containing reagents are employed, such as dimethyldioxirane. Depending on the mechanism of the reaction and the geometry of the starting material. In addition, if there are other stereocenters present in the starting material, the metal-catalyzed epoxidation was first explored using tert-butyl hydroperoxide as a source of an O atom. Association of TBHP with the metal generates the active metal catalyst with a peroxy ligand and this approach is used for the production of propylene oxide from propylene using various catalysts. Both t-butyl hydroperoxide or ethylbenzene hydroperoxide can be used as oxygen sources, more typically for laboratory operations, the Prilezhaev reaction is employed. This approach involves the oxidation of the alkene with a such as m-CPBA. Illustrative is the epoxidation of styrene with perbenzoic acid to styrene oxide, the peroxide is viewed as an electrophile, and the alkene a nucleophile. The reaction is considered to be concerted. The butterfly mechanism allows ideal positioning of the O-O sigma star orbital for C-C Pi electrons to attack, hydroperoxides are also employed in catalytic enantioselective epoxidations, such as the Sharpless epoxidation and the Jacobsen epoxidation. Together with the Shi epoxidation, these reactions are useful for the synthesis of chiral epoxides
2.
Polymer
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A polymer is a large molecule, or macromolecule, composed of many repeated subunits. Because of their range of properties, both synthetic and natural polymers play an essential and ubiquitous role in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure, Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. The units composing polymers derive, actually or conceptually, from molecules of low molecular mass. The term was coined in 1833 by Jöns Jacob Berzelius, though with a distinct from the modern IUPAC definition. The modern concept of polymers as covalently bonded macromolecular structures was proposed in 1920 by Hermann Staudinger, Polymers are studied in the fields of biophysics and macromolecular science, and polymer science. Polyisoprene of latex rubber is an example of a polymer. In biological contexts, essentially all biological macromolecules—i. e, proteins, nucleic acids, and polysaccharides—are purely polymeric, or are composed in large part of polymeric components—e. g. Isoprenylated/lipid-modified glycoproteins, where small molecules and oligosaccharide modifications occur on the polyamide backbone of the protein. The simplest theoretical models for polymers are ideal chains, Polymers are of two types, Natural polymeric materials such as shellac, amber, wool, silk and natural rubber have been used for centuries. A variety of natural polymers exist, such as cellulose. Most commonly, the continuously linked backbone of a used for the preparation of plastics consists mainly of carbon atoms. A simple example is polyethylene, whose repeating unit is based on ethylene monomer, however, other structures do exist, for example, elements such as silicon form familiar materials such as silicones, examples being Silly Putty and waterproof plumbing sealant. Oxygen is also present in polymer backbones, such as those of polyethylene glycol, polysaccharides. Polymerization is the process of combining many small molecules known as monomers into a covalently bonded chain or network, during the polymerization process, some chemical groups may be lost from each monomer. This is the case, for example, in the polymerization of PET polyester, the distinct piece of each monomer that is incorporated into the polymer is known as a repeat unit or monomer residue. Laboratory synthetic methods are divided into two categories, step-growth polymerization and chain-growth polymerization. However, some methods such as plasma polymerization do not fit neatly into either category
3.
Cross-link
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A cross-link is a bond that links one polymer chain to another. They can be covalent bonds or ionic bonds, polymer chains can refer to synthetic polymers or natural polymers. When the term cross-linking is used in the synthetic polymer science field, cross-linking is used in both synthetic polymer chemistry and in the biological sciences. Although the term is used to refer to the linking of polymer chains for both sciences, the extent of crosslinking and specificities of the crosslinking agents vary. Of course, with all science, there are overlaps, when cross links are added to long rubber molecules, the flexibility decreases, the hardness increases and the melting point increases as well. When polymer chains are linked together by cross-links, they some of their ability to move as individual polymer chains. How the crosslinking process works and how it improves the properties of polymers is nicely illustrated in this video-animation, for example, a liquid polymer can be turned into a solid or gel by cross-linking the chains together. In polymer chemistry, when a polymer is said to be cross-linked. The resulting modification of mechanical properties depends strongly on the cross-link density, low cross-link densities decrease the viscosities of polymer melts. Intermediate cross-link densities transform gummy polymers into materials that have elastomeric properties, very high cross-link densities can cause materials to become very rigid or glassy, such as phenol-formaldehyde materials. Cross-links can be formed by reactions that are initiated by heat, pressure, change in pH. For example, mixing of an unpolymerized or partially polymerized resin with specific chemicals called crosslinking reagents results in a reaction that forms cross-links. Cross-linking can also be induced in materials that are normally thermoplastic through exposure to a source, such as electron beam exposure, gamma-radiation. For example, electron beam processing is used to cross-link the C type of cross-linked polyethylene, the chemical process of vulcanization is a type of cross-linking that changes rubber to the hard, durable material associated with car and bike tires. This process is often called sulfur curing, the term comes from Vulcan. This is, however, a slower process, a typical car tire is cured for 15 minutes at 150 °C. However, the time can be reduced by the addition of such as 2-benzothiazolethiol or tetramethylthiuram disulfide. Both of these contain an atom in the molecule that initiates the reaction of the sulfur chains with the rubber
4.
Thiol
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In organic chemistry, a thiol is an organosulfur compound that contains a carbon-bonded sulfhydryl or sulphydryl group. Thiols are the analogue of alcohols, and the word is a portmanteau of thion + alcohol. The –SH functional group itself is referred to as either a group or a sulfhydryl group. Many thiols have strong odors resembling that of garlic or rotten eggs, thiols are used as odorants to assist in the detection of natural gas, and the smell of natural gas is due to the smell of the thiol used as the odorant. Thiols are sometimes referred to as mercaptans, thiols and alcohols have similar connectivity. Because sulfur is a larger element than oxygen, the C–S bond lengths, the C–S–H angles approach 90° whereas the angle for the C-O-H group are more open. In the solid or liquids, the hydrogen-bonding between individual groups is weak, the main cohesive force being van der Waals interactions between the highly polarizable divalent sulfur centers. Due to the lesser electronegativity difference between sulfur and hydrogen compared to oxygen and hydrogen, an S–H bond is less polar than the hydroxyl group, thiols have a lower dipole moment relative to the corresponding alcohol. There are several ways to name the alkylthiols, The suffix -thiol is added to the name of the alkane and this method is nearly identical to naming an alcohol and is used by the IUPAC. The word mercaptan replaces alcohol in the name of the equivalent alcohol compound, example, CH3SH would be methyl mercaptan, just as CH3OH is called methyl alcohol. The term sulfanyl or mercapto is used as a prefix, many thiols have strong odors resembling that of garlic. The odors of thiols, particularly those of low weight, are often strong. The spray of skunks consists mainly of low-molecular-weight thiols and derivatives and these compounds are detectable by the human nose at concentrations of only 10 parts per billion. Human sweat contains /-3-methyl-3-sulfanylhexan-1-ol, detectable at 2 parts per billion and having a fruity, methanethiol is a strong-smelling volatile thiol, also detectable at parts per billion levels, found in male mouse urine. Lawrence C. Katz and co-workers showed that MTMT functioned as a semiochemical, activating certain mouse olfactory sensory neurons, attracting female mice. Copper has been shown to be required by a specific mouse olfactory receptor, MOR244-3, thiols are also responsible for a class of wine faults caused by an unintended reaction between sulfur and yeast and the skunky odor of beer that has been exposed to ultraviolet light. Not all thiols have unpleasant odors, for example, furan-2-ylmethanethiol contributes to the aroma of roasted coffee, whereas grapefruit mercaptan, a monoterpenoid thiol, is responsible for the characteristic scent of grapefruit. The effect of the compound is present only at low concentrations
5.
Fibre-reinforced plastic
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Fibre-reinforced plastic is a composite material made of a polymer matrix reinforced with fibres. The fibres are usually glass, carbon, aramid, or basalt, rarely, other fibres such as paper or wood or asbestos have been used. The polymer is usually an epoxy, vinylester or polyester thermosetting plastic, FRPs are commonly used in the aerospace, automotive, marine, and construction industries. They are commonly found in ballistic armor as well, a polymer is generally manufactured by step-growth polymerization or addition polymerization. When combined with various agents to enhance or in any way alter the properties of polymers the result is referred to as a plastic. Fibre-reinforced plastics are a category of composite plastics that specifically use fibre materials to enhance the strength. The original plastic material without fibre reinforcement is known as the matrix or binding agent, the matrix is a tough but relatively weak plastic that is reinforced by stronger stiffer reinforcing filaments or fibres. Reinforcement of the matrix occurs by definition when the FRP material exhibits increased strength or elasticity relative to the strength, bakelite was the first fibre-reinforced plastic. Dr. Leo Baekeland had originally set out to find a replacement for shellac, chemists had begun to recognize that many natural resins and fibres were polymers, and Baekeland investigated the reactions of phenol and formaldehyde. By controlling the pressure and temperature applied to phenol and formaldehyde, he found in 1905 he could produce his dreamed-of hard mouldable material and he announced his invention at a meeting of the American Chemical Society on February 5,1909. The development of fibre-reinforced plastic for use was being extensively researched in the 1930s. In the UK, considerable research was undertaken by such as Norman de Bruyne. It was particularly of interest to the aviation industry, a patent for this method of producing glass wool was first applied for in 1933. Owens joined with the Corning company in 1935 and the method was adapted by Owens Corning to produce its patented fibreglas in 1936, originally, fibreglas was a glass wool with fibres entrapping a great deal of gas, making it useful as an insulator, especially at high temperatures. A suitable resin for combining the fibreglas with a plastic to produce a material, was developed in 1936 by du Pont. The first ancestor of modern polyester resins is Cyanamids resin of 1942, peroxide curing systems were used by then. With the combination of fibreglas and resin the gas content of the material was replaced by plastic and this reduced to insulation properties to values typical of the plastic, but now for the first time the composite showed great strength and promise as a structural and building material. Confusingly, many glass fibre composites continued to be called fibreglass, ray Greene of Owens Corning is credited with producing the first composite boat in 1937, but did not proceed further at the time due to the brittle nature of the plastic used
6.
Adhesive
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The use of adhesives offers many advantages over binding techniques such as sewing, mechanical fastening, thermal bonding, etc. Adhesives are typically organized by the method of adhesion and these are then organized into reactive and non-reactive adhesives, which refers to whether the adhesive chemically reacts in order to harden. Alternatively they can be organized by whether the raw stock is of natural or synthetic origin, Adhesives may be found naturally or produced synthetically. The earliest human use of substances was approximately 200,000 years ago. The first references to adhesives in literature first appeared in approximately 2000 BCE, the Greeks and Romans made great contributions to the development of adhesives. In Europe, glue was not widely used until the period 1500–1700 CE, from then until the 1900s increases in adhesive use and discovery were relatively gradual. Only since the last century has the development of synthetic adhesives accelerated rapidly, the earliest use of adhesives was discovered in central Italy when two stone flakes partially covered with birch-bark tar and a third uncovered stone from the Middle Pleistocene era were found. This is thought to be the oldest discovered human use of tar-hafted stones, the birch-bark-tar adhesive is a simple, one-component adhesive. Although sticky enough, plant-based adhesives are brittle and vulnerable to environmental conditions, the first use of compound adhesives was discovered in Sibudu, South Africa. The ability to produce stronger adhesives allowed middle stone age humans to attach stone segments to sticks in greater variations, more recent examples of adhesive use by prehistoric humans have been found at the burial sites of ancient tribes. Archaeologists studying the sites found that approximately 6,000 years ago the tribesmen had buried their dead together with food found in clay pots repaired with tree resins. The glue was analyzed as pitch, which requires the heating of tar during its production, the retrieval of this tar requires a transformation of birch bark by means of heat, in a process known as pyrolysis. The first references to adhesives in literature first appeared in approximately 2000 BCE, further historical records of adhesive use are found from the period spanning 1500–1000 BCE. Artifacts from this period include paintings depicting wood gluing operations and a made of wood. Other ancient Egyptian artifacts employ animal glue for bonding or lamination, such lamination of wood for bows and furniture is thought to have extended their life and was accomplished using casein -based glues. The ancient Egyptians also developed starch-based pastes for the bonding of papyrus to clothing, from 1 to 500 AD the Greeks and Romans made great contributions to the development of adhesives. Wood veneering and marquetry were developed, the production of animal and fish glues refined, egg-based pastes were used to bond gold leaves incorporated various natural ingredients such as blood, bone, hide, milk, cheese, vegetables, and grains. The Greeks began the use of slaked lime as mortar while the Romans furthered mortar development by mixing lime with volcanic ash and this material, known as pozzolanic cement, was used in the construction of the Roman Colosseum and Pantheon
7.
Petroleum
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Petroleum is a naturally occurring, yellow-to-black liquid found in geological formations beneath the Earths surface, which is commonly refined into various types of fuels. Components of petroleum are separated using a technique called fractional distillation and it consists of hydrocarbons of various molecular weights and other organic compounds. The name petroleum covers both naturally occurring unprocessed crude oil and petroleum products that are made up of refined crude oil. A fossil fuel, petroleum is formed when large quantities of dead organisms, usually zooplankton and algae, are buried underneath sedimentary rock, Petroleum has mostly been recovered by oil drilling. Drilling is carried out studies of structural geology, sedimentary basin analysis. Petroleum is used in manufacturing a variety of materials. Concern over the depletion of the earths finite reserves of oil, the burning of fossil fuels plays the major role in the current episode of global warming. The word petroleum comes from Greek, πέτρα for rocks and Greek, the term was found in 10th-century Old English sources. It was used in the treatise De Natura Fossilium, published in 1546 by the German mineralogist Georg Bauer, Petroleum, in one form or another, has been used since ancient times, and is now important across society, including in economy, politics and technology. Great quantities of it were found on the banks of the river Issus, ancient Persian tablets indicate the medicinal and lighting uses of petroleum in the upper levels of their society. By 347 AD, oil was produced from bamboo-drilled wells in China, early British explorers to Myanmar documented a flourishing oil extraction industry based in Yenangyaung that, in 1795, had hundreds of hand-dug wells under production. The mythological origins of the oil fields at Yenangyaung, and its hereditary monopoly control by 24 families, Pechelbronn is said to be the first European site where petroleum has been explored and used. The still active Erdpechquelle, a spring where petroleum appears mixed with water has been used since 1498, Oil sands have been mined since the 18th century. In Wietze in lower Saxony, natural asphalt/bitumen has been explored since the 18th century, both in Pechelbronn as in Wietze, the coal industry dominated the petroleum technologies. In 1848 Young set up a small business refining the crude oil, Young eventually succeeded, by distilling cannel coal at a low heat, in creating a fluid resembling petroleum, which when treated in the same way as the seep oil gave similar products. The production of oils and solid paraffin wax from coal formed the subject of his patent dated 17 October 1850. In 1850 Young & Meldrum and Edward William Binney entered into partnership under the title of E. W. Binney & Co. at Bathgate in West Lothian, the worlds first oil refinery was built in 1856 by Ignacy Łukasiewicz. The demand for petroleum as a fuel for lighting in North America, edwin Drakes 1859 well near Titusville, Pennsylvania, is popularly considered the first modern well
8.
Epichlorohydrin
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Epichlorohydrin is an organochlorine compound and an epoxide. Despite its name, it is not a halohydrin and it is a colorless liquid with a pungent, garlic-like odor, moderately soluble in water, but miscible with most polar organic solvents. It is a chiral molecule generally existing as a mixture of right-handed and left-handed enantiomers. Epichlorohydrin is a reactive compound and is used in the production of glycerol, plastics, epoxy glues and resins. In contact with water, epichlorohydrin hydrolyzes to 3-MCPD, a found in food. Epichlorohydrin was first described in 1848 by Marcellin Berthelot, the compound was isolated during studies on reactions between glycerol and gaseous hydrogen chloride. Glycerol is a co-product of biodiesel produced on a large scale, the conversion of glycerol into other building block chemicals is of interest because glycerol is otherwise hard to dispose of. Dow and Solvay are building glycerol-to-epichlorohydrin plants in Shanghai and Thailand, in Dows process, glycerol is dichlorinated with hydrogen chloride with the help of a carboxylic acid catalyst. The mixture of dichlorohydroxypropanes is treated with base to form epichlorohydrin, epichlorohydrin is mainly converted to bisphenol A diglycidyl ether, a building block in the manufacture of epoxy resins. It is also a precursor to monomers for other resins and polymers, synthetic glycerol is now used only in sensitive pharmaceutical, technical and personal care applications where quality standards are very high. Epichlorohydrin is a precursor in the synthesis of many organic compounds. For example, it is converted to nitrate, an energetic binder used in explosive. The epichlorohydrin is reacted with an alkali nitrate, such as nitrate, producing glycidyl nitrate. It is used as a solvent for cellulose, resins, and paints, an important biochemical application of epichlorohydrin is its use as crosslinking agent for the production of Sephadex size-exclusion chromatographic resins from dextrans. Epichlorohydrin is classified by several health research agencies and groups as a probable or likely carcinogen in humans. Prolonged oral consumption of high levels of epichlorohydrin could result in stomach problems, occupational exposure to epichlorohydrin via inhalation could result in lung irritation and an increased risk of lung cancer
9.
Stoichiometry
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Stoichiometry /ˌstɔɪkiˈɒmᵻtri/ is the calculation of relative quantities of reactants and products in chemical reactions. This means that if the amounts of the reactants are known. Conversely, if one reactant has a quantity and the quantity of product can be empirically determined. This is illustrated in the image here, where the equation is. Here, one molecule of methane reacts with two molecules of gas to yield one molecule of carbon dioxide and two molecules of water. Stoichiometry measures these quantitative relationships, and is used to determine the amount of products/reactants that are produced/needed in a given reaction, describing the quantitative relationships among substances as they participate in chemical reactions is known as reaction stoichiometry. In the example above, reaction stoichiometry measures the relationship between the methane and oxygen as they react to form carbon dioxide and water. Gas stoichiometry deals with reactions involving gases, where the gases are at a temperature, pressure. For gases, the ratio is ideally the same by the ideal gas law. In practice, due to the existence of isotopes, molar masses are used instead when calculating the mass ratio, the term stoichiometry was first used by Jeremias Benjamin Richter in 1792 when the first volume of Richters Stoichiometry or the Art of Measuring the Chemical Elements was published. The term is derived from the Greek words στοιχεῖον stoicheion element, in patristic Greek, the word Stoichiometria was used by Nicephorus to refer to the number of line counts of the canonical New Testament and some of the Apocrypha. In general, chemical reactions combine in definite ratios of chemicals, since chemical reactions can neither create nor destroy matter, nor transmute one element into another, the amount of each element must be the same throughout the overall reaction. Chemical reactions, as unit operations, consist of simply a very large number of elementary reactions. As the reacting molecules consist of a set of atoms in an integer ratio. A reaction may consume more than one molecule, and the number counts this number, defined as positive for products. Different elements have a different atomic mass, and as collections of atoms, molecules have a definite molar mass. By definition, carbon-12 has a mass of 12 g/mol. The mass ratios can be calculated by dividing each by the total in the whole reaction, Elements in their natural state are mixtures of isotopes of differing mass, thus atomic masses and thus molar masses are not exactly integers
10.
Bisphenol A
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Bisphenol A is an organic synthetic compound with the chemical formula 2C2 belonging to the group of diphenylmethane derivatives and bisphenols, with two hydroxyphenyl groups. It is a solid that is soluble in organic solvents. It has been in use since 1957. BPA is employed to make certain plastics and epoxy resins, bPA-based plastic is clear and tough, and is made into a variety of common consumer goods, such as water bottles, sports equipment, CDs, and DVDs. Epoxy resins containing BPA are used to water pipes, as coatings on the inside of many food and beverage cans. In 2015, an estimated 4 million tonnes of BPA chemical were produced for manufacturing polycarbonate plastic, BPA exhibits estrogen mimicking, hormone-like properties that raise concern about its suitability in some consumer products and food containers. Since 2008, several governments have investigated its safety, which prompted some retailers to withdraw polycarbonate products. The U. S. Food and Drug Administration has ended its authorization of the use of BPA in baby bottles and infant formula packaging, based on market abandonment, the European Union and Canada have banned BPA use in baby bottles. The FDA states BPA is safe at the current levels occurring in foods based on extensive research, in February 2016, France announced that it intends to propose BPA as a REACH Regulation candidate substance of very high concern. World production capacity of Bisphenol A was 1 million tons in the 1980s and it is a high production volume chemical. In 2003, U. S. consumption was 856,000 tons, 72% of which used to make polycarbonate plastic and 21% going into epoxy resins. In the U. S. less than 5% of the BPA produced is used in food contact applications, Bisphenol A was first synthesized by the Russian chemist Alexander Dianin in 1891. This compound is synthesized by the condensation of acetone with two equivalents of phenol, the reaction is catalyzed by a strong acid, such as hydrochloric acid or a sulfonated polystyrene resin. Bisphenol A is used primarily to make plastics, and products using bisphenol A-based plastics have been in use since 1957. At least 3.6 million tonnes of BPA are used by manufacturers yearly and it is a key monomer in production of epoxy resins and in the most common form of polycarbonate plastic. Bisphenol A and phosgene react to give polycarbonate under biphasic conditions, phenol is eliminated instead of hydrochloric acid. This transesterification process avoids the toxicity and handling of phosgene, BPA is also used in the synthesis of polysulfones and polyether ketones, as an antioxidant in some plasticizers, and as a polymerization inhibitor in PVC. Bisphenol A is also a precursor to the flame retardant tetrabromobisphenol A, Bisphenol A is a preferred color developer in carbonless copy paper and thermal point of sale receipt paper
11.
Thermoplastic
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A thermoplastic, or thermosoftening plastic, is a plastic material, a polymer, that becomes pliable or moldable above a specific temperature and solidifies upon cooling. Most thermoplastics have a molecular weight. The polymer chains associate through intermolecular forces, which weaken rapidly with increased temperature, thermoplastics differ from thermosetting polymers, which form irreversible chemical bonds during the curing process. Thermosets do not melt, but decompose and do not reform upon cooling, above its glass transition temperature and below its melting point, the physical properties of a thermoplastic change drastically without an associated phase change. Some thermoplastics do not fully crystallize below the transition temperature. Amorphous and semi-amorphous plastics are used when high optical clarity is necessary, amorphous and semi-amorphous plastics are less resistant to chemical attack and environmental stress cracking because they lack a crystalline structure. Brittleness can be decreased with the addition of plasticizers, which increases the mobility of amorphous chain segments to effectively lowers the transition temperature. Modification of the polymer through copolymerization or through the addition of side chains to monomers before polymerization can also lower it. Naval Research Laboratory developed thermoplastic armor, that can be repaired in the field by a user via tools for pressing irons, acrylic, a polymer called poly, is also known by trade names such as Lucite, Perspex and Plexiglas. It serves as a substitute for glass for items such as aquariums, motorcycle helmet visors, aircraft windows, viewing ports of submersibles. It is extensively used to make signs, including lettering and logos, in medicine, it is used in bone cement and to replace eye lenses. Acrylic paint consists of PMMA particles suspended in water, acrylonitrile butadiene styrene is a terpolymer synthesized from styrene and acrylonitrile in the presence of polybutadiene. ABS is a material that exhibits high impact resistance and mechanical toughness. It poses few risks to health under normal handling. It is used in consumer products, such as toys, appliances. Nylon belongs to a class of polymers called polyamides and it has served as a substitute mainly for hemp, cotton and silk, in products such as parachutes, cords, sails, flak vests and womens clothing. Nylon fibers are useful in making fabrics, rope, carpets and musical strings, whereas in bulk form, Nylon is used for mechanical parts including machine screws, gears, in addition, it is used in the manufacture of heat-resistant composite materials. Polylactic acid is a biodegradable thermoplastic aliphatic polyester derived from renewable resources, such as starch, tapioca roots, chips or starch
12.
Isocyanate
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Isocyanate is the functional group with the formula R–N=C=O. Organic compounds that contain a group are referred to as isocyanates. An isocyanate that has two groups is known as a di-isocyanate. Di-isocyanates are manufactured for reactions with polyols in the production of polyurethanes, isocyanates should not be confused with cyanate esters and isocyanides, whose behaviors are very different. The cyanate functional group is arranged differently from the isocyanate group, isocyanides have the connectivity R-N≡C, lacking the oxygen of the cyanate groups. Isocyanates are produced by treating amines with phosgene, RNH2 + COCl2 → RNCO +2 HCl These reactions proceed via the intermediacy of a carbamoyl chloride, owing to the hazards associated with phosgene, the production of isocyanates requires special precautions. Isocyanates are electrophiles, and as such they are reactive toward a variety of nucleophiles including alcohols, amines, isocyanates react with water to form carbon dioxide, RNCO + H2O → RNH2 + CO2 This reaction is exploited in tandem with the production of polyurethane to give polyurethane foams. The carbon dioxide functions as a blowing agent, isocyanates also can react with themselves. Aliphatic di-isocyanates can form trimers, which are related to cyanuric acid. Isocyanates participate in Diels-Alder reactions, functioning as dienophiles, schmidt reaction, a reaction where a carboxylic acid is treated with ammonia and hydrazoic acid yielding an isocyanate. Curtius rearrangement degradation of an azide to an isocyanate and nitrogen gas. Lossen rearrangement, the conversion of an acid to an isocyanate via the formation of an O-acyl, sulfonyl. A monofunctional isocyanate of industrial significance is methyl isocyanate, which is used in the manufacture of pesticides, lD50s are typically several hundred milligrams per kilogram. Isocyanates are potentially dangerous irritants to the eyes and respiratory tract, methyl isocyanate was the chemical released in the Bhopal disaster causing the death of nearly 4000 people. Polyurethanes have variable curing times, and the presence of free isocyanates in foams vary accordingly, prepared by the Institute of Occupational Medicine for the Health and Safety Executive
13.
Bisphenol
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The bisphenols are a group of chemical compounds with two hydroxyphenyl functionalities. Most of them are based on diphenylmethane, the exceptions are bisphenol S, P, and M. Bisphenol is a common name, the letter following refers to one of the reactants. Bisphenol A is the most popular representative of this group, often simply called bisphenol, Bisphenol A diglycidyl ether is another bisphenol derivative, along with EPI-001. Bisphenols A and S have been shown to be endocrine disruptors, due to its high production volumes BPA has been characterised as a pseudo-persistent chemical, leading to its spreading and potential accumulation in a variety of environmental matrices
14.
Exothermic reaction
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An exothermic reaction is a chemical reaction that releases energy by light or heat. It is the opposite of an endothermic reaction, expressed in a chemical equation, reactants → products + energy An exothermic reaction is a chemical or physical reaction that releases heat. It gives net energy to its surroundings and that is, the energy needed to initiate the reaction is less than the energy released. When the medium in which the reaction is taking place gains heat, when using a calorimeter, the total amount of heat that flows into the calorimeter is the negative of the net change in energy of the system. The absolute amount of energy in a system is difficult to measure or calculate. The enthalpy change, ΔH, of a reaction is much easier to work with. The enthalpy change equals the change in energy of the system plus the work needed to change the volume of the system against constant ambient pressure. A bomb calorimeter is very suitable for measuring the change, ΔH. In endergonic reactions and exergonic reactions it is the sign of the Gibbs free energy that determines the equilibrium point, the related concepts endergonic and exergonic apply to all physical processes. The conceptually related endotherm and ectotherm are concepts in animal physiology, in quantum numbers, when any excited energy level goes down to its original level for example, when n=4 fall to n=2, energy is released so, it is exothermic. Where an exothermic reaction causes heating of the vessel which is not controlled. This positive feedback situation is known as thermal runaway, an explosion can also result from the problem. Heat production or absorption in either a process or chemical reaction is measured using calorimetry. One common laboratory instrument is the calorimeter, where the heat flow into or from the reaction vessel is monitored. The technique can be used to follow chemical reactions as well as physical processes such as crystallization and dissolution, energy released is measured in Joule per mole. The reaction has a negative ΔH value due to heat loss, E. g. -123 J/mol Chemical thermodynamics Differential scanning calorimetry Endergonic Exergonic Endergonic reaction Exergonic reaction Exothermic Endothermic reaction Endotherm
15.
Copolymer
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When two or more different monomers unite together to polymerize, their result is called a copolymer and its process is called copolymerization. Commercially relevant copolymers include acrylonitrile butadiene styrene, styrene/butadiene co-polymer, nitrile rubber, styrene-acrylonitrile, styrene-isoprene-styrene, since a copolymer consists of at least two types of constituent units, copolymers can be classified based on how these units are arranged along the chain. Block copolymers comprise two or more homopolymer subunits linked by covalent bonds, the union of the homopolymer subunits may require an intermediate non-repeating subunit, known as a junction block. Block copolymers with two or three blocks are called diblock copolymers and triblock copolymers, respectively. Copolymers may also be described in terms of the existence of or arrangement of branches in the polymer structure, linear copolymers consist of a single main chain whereas branched copolymers consist of a single main chain with one or more polymeric side chains. Other special types of branched copolymers include star copolymers, brush copolymers, in gradient copolymers the monomer composition changes gradually along the chain. A terpolymer is a copolymer consisting of three distinct monomers, the term is derived from ter, meaning thrice, and polymer. Stereoblock copolymers A special structure can be formed from one monomer where now the distinguishing feature is the tacticity of each block, statistical copolymers are dictated by the reaction kinetics of the two chemically distinct monomer reactants, and are commonly referred to interchangeably as “random” in the polymer literature. As with other types of copolymers, random copolymers can have interesting, examples of commercially relevant random copolymers include rubbers made from styrene-butadiene copolymers and resins from styrene-acrylic or methacrylic acid derivatives. A number of parameters are relevant in the composition of the product, namely. Reactivity ratios describe whether the monomer reacts preferentially with a segment of the type or of the other type. For example, a reactivity ratio that is less one for component 1 indicates that this component reacts with the other type of monomer more readily. When both reactivity ratios are less than one, there is a point in the Mayo-Lewis plot. At this point, the fraction of monomer equals the composition of the component in the polymer. There are several ways to synthesize random copolymers, free radical polymerization is less expensive than other methods, and produces high-molecular weight polymer quickly. Several methods offer better control over dispersity, additionally, anionic polymerization is expensive and requires very clean reaction conditions, and is therefore difficult to implement on a large scale. These methods are favored over anionic polymerization because they can be performed in similar to free radical polymerization. The reactions require longer periods than free radical polymerization
16.
Glass transition
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An amorphous solid that exhibits a glass transition is called a glass. The reverse transition, achieved by supercooling a viscous liquid into the state, is called vitrification. The glass-transition temperature Tg of a material characterizes the range of temperatures over which this transition occurs. It is always lower than the temperature, Tm, of the crystalline state of the material. Hard plastics like polystyrene and poly are used well below their glass transition temperatures, such conventions include a constant cooling rate and a viscosity threshold of 1012 Pa·s, among others. The question of whether some phase transition underlies the glass transition is a matter of continuing research, the glass transition of a liquid to a solid-like state may occur with either cooling or compression. The transition comprises a smooth increase in the viscosity of a material by as much as 17 orders of magnitude without any pronounced change in material structure, the consequence of this dramatic increase is a glass exhibiting solid-like mechanical properties on the timescale of practical observation. In many materials that undergo a freezing transition, rapid cooling will avoid this phase transition. Other materials, such as polymers, lack a well defined crystalline state and easily form glasses. The tendency for a material to form a glass while quenched is called glass forming ability and this ability depends on the composition of the material and can be predicted by the rigidity theory. Below the transition temperature range, the structure does not relax in accordance with the cooling rate used. The expansion coefficient for the state is roughly equivalent to that of the crystalline solid. If slower cooling rates are used, the time for structural relaxation to occur may result in a higher density glass product. Similarly, by annealing the glass structure in time approaches an equilibrium density corresponding to the liquid at this same temperature. Tg is located at the intersection between the curve for the glassy state and the supercooled liquid. The configuration of the glass in this range changes slowly with time towards the equilibrium structure. The principle of the minimization of the Gibbs free energy provides the driving force necessary for the eventual change. It should be noted here that at higher temperatures than Tg
17.
Addition reaction
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An addition reaction, in organic chemistry, is in its simplest terms an organic reaction where two or more molecules combine to form a larger one. Addition reactions are limited to chemical compounds that have multiple bonds, such as molecules with double bonds. Molecules containing carbon—hetero double bonds like carbonyl groups, or imine groups, can undergo addition, an addition reaction is the reverse of an elimination reaction. For instance, the hydration of an alkene to an alcohol is reversed by dehydration, there are two main types of polar addition reactions, electrophilic addition and nucleophilic addition. Two non-polar addition reactions exist as well, called free-radical addition, addition reactions are also encountered in polymerizations and called addition polymerization. In the related addition-elimination reaction an addition reaction is followed by an elimination reaction, in the majority of reactions it involves addition of nucleophiles to carbonyl compounds in what is called nucleophilic acyl substitution. Other addition-elimination reactions are the reaction of an amine to an imine. The hydrolysis of nitriles to carboxylic acids is also a form of addition-elimination
18.
Powder coating
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Powder Coating is a type of coating that is applied as a free-flowing, dry powder. The main difference between a conventional liquid paint and a coating is that the powder coating does not require a solvent to keep the binder and filler parts in a liquid suspension form. The coating is typically applied electrostatically and is cured under heat to allow it to flow. The powder may be a thermoplastic or a thermoset polymer and it is usually used to create a hard finish that is tougher than conventional paint. Powder coating is used for coating of metals, such as household appliances, aluminum extrusions, drum hardware. Newer technologies allow other materials, such as MDF, to be powder coated using different methods, because no carrier fluid evaporates away, the coating process emits few volatile organic compounds. Finally, several powder colors can be applied before curing them all together, allowing color blending, while it is relatively easy to apply thick coatings which cure to smooth, texture-free coating, it is not as easy to apply smooth thin films. As the film thickness is reduced, the film more and more orange peeled in texture due to the particle size. For such powder coatings, film build-ups of greater than 50 μ may be required to obtain an acceptably smooth film, the surface texture which is considered desirable or acceptable depends on the end product. There are very specialized operations where powder coatings of less than 30 micrometres or with a Tg below 40 °C are used in order to produce thin films. For garage-scale jobs, small rattle can spray paint are less expensive, at the professional scale, the capital expense and time required for a powder coat gun, booth and oven are similar to a spray gun system. Powder coatings have an advantage in that the overspray can be recycled. However, if multiple colors are being sprayed in a spray booth. Powder coatings contain no solvents and releases negligible amounts of Volatile Organic Compounds into the atmosphere, powder coatings can produce much thicker coatings than conventional liquid coatings without running or sagging. Powder coated items generally have fewer appearance differences between horizontally coated surfaces and vertically coated surfaces than liquid coated items, the wide range of specialty effects are easily accomplished using powder coatings that would be impossible to achieve with other coating processes. There are two categories of powder coating, thermosets and thermoplastics. The thermosetting variety incorporates a cross-linker into the formulation, when the powder is baked, it reacts with other chemical groups in the powder to polymerize, improving the performance properties. The thermoplastic variety does not undergo any additional actions during the baking process, the most common polymers used are polyester, polyurethane, polyester-epoxy, straight epoxy and acrylics. is essential prior to the powder coating process
19.
Rock bolt
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A rock bolt is a long anchor bolt, for stabilizing rock excavations, which may be used in tunnels or rock cuts. It transfers load from the exterior to the confined interior of the rock mass. Rock bolts were first used in mining in the 1890s, with systematic use documented at the St Joseph Lead Mine in the U. S. in the 1920s. Rock bolts were applied to civil tunneling support in the U. S. as shown in the figure, rock bolts are almost always installed in a pattern, the design of which depends on the rock quality designation and the type of excavation. Rock bolts are a component of the New Austrian Tunneling method. As with anchor bolts, there are many proprietary rock bolt designs, there are also fiberglass bolts which can be cut through again by subsequent excavation. Many papers have written on methods of rock bolt design. Rock bolts work by knitting the rock mass together sufficiently before it can move enough to loosen, as in the photo, rock bolts may be used to support wire mesh, but this is usually a small part of their function. Unlike common anchor bolts, rock bolts can become seized throughout their length by small shears in the rock mass, so they are not fully dependent on their pull-out strength. This has become an item of controversy in the Big Dig project, rock bolts can also be used to prevent rockfall
20.
Anchor bolt
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An anchor bolt is a fastener used to attach objects or structures to concrete. There are many types of bolts, consisting of designs that are mostly proprietary to the manufacturing companies. All consist of an end, to which a nut. Anchor bolts are used on all types of projects, from standard buildings to dams. They can also be used to firmly affix embed plates to a concrete foundation when used with a structural steel element, the simplest anchor bolt is a cast-in-place anchor. As seen in the figure, most designs consist of a bolt with a hexagonal head. There are other designs, some consisting of a bent bolt with a hook on the end, cast-in-place anchor bolts are the strongest type of fastener, but the casting is difficult, and they are usually only used for heavy machines mounted on poured concrete floors. Another use of this anchor bolt is to connect the foundation of a building to its wall. With this, the building is more resistant to earthquakes, currently there are several devices to assist in holding and in placing anchor bolt to set in the concrete. These devices are made from composite plastic. Once the concrete has been poured and set, the other types of bolts that can be used are mechanical. Epoxy bolts are the strongest, but can be tricky to install, since the epoxy has to be mixed to exact specifications, the hole must be very clean. As well, there must be a testing program. In Bostons Big Dig project, these procedures were not well carried out, a concrete screw is another way of attaching things to concrete that has already been poured and set. Wedge anchors, also known as bolts and expansion anchors. There are three styles of wedge anchors, fully threaded, partial threaded and the full-bodied wedge anchor. As shown in the figure, tightening the bolt results in a wedge being driven up against a sleeve and this jams the end of the bolt, and provides the strength. Many different manufacturers provide a variation on this theme, usually depending on the condition of the concrete, a specialized form of the anchor bolt is the rock bolt, used in rock excavations
21.
Ciba Specialty Chemicals
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Ciba was a chemical company based in and near Basel, Switzerland. Ciba stood for Chemische Industrie Basel and it was formed as the non-pharmaceuticals elements of Novartis were spun out in 1997, following the merger in the previous year of Ciba-Geigy and Sandoz that created Novartis. In 2008, Ciba was acquired by the German chemical company BASF and, in April 2009, Ciba AG initially continued to trade under the old name, but was renamed to BASF Schweiz AG in March 2010. In 2004 Ciba bought paper chemical manufacturer Raisio Chemicals from Raisio Group, in 2006, Ciba divested its Textile Dyes and Chemical Auxiliaries business in a sale to Huntsman Corporation. In 2007 the company announced the intention to adopt the name Ciba Inc
22.
Huntsman Corporation
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Huntsman Corporation is an American multinational manufacturer and marketer of chemical products for consumers and industrial customers. Huntsman manufactures assorted polyurethanes, performance products, and pigments for customers like BMW, GE, Chevron, Procter & Gamble, Huntsman Corporation had 2016 revenues of approximately $10 billion. The Huntsman Corporation was initially founded as the Huntsman Container Corporation in 1970 by Jon Huntsman and it went public as the Huntsman Corporation on the New York Stock Exchange NYSE, HUN in February 2005. Huntsman has grown through a series of acquisitions and today is a manufacturer and marketer of differentiated chemical products, in April 1994, Huntsman acquired the Texaco Chemical company for $1.06 billion. Texaco Inc. agreed to sell its last remaining petrochemicals plant to Huntsman in 1999 for about $600 million.8 billion, Huntsman paid approximately $1 billion in cash and assumed certain unfunded European pension liabilities. Advanced Materials is a supplier of synthetic and formulated polymer systems, huntsman’s epoxy, acrylic and polyurethane-based polymer products are used to replace traditional materials in aircraft, automobiles and electrical power transmission. Polyurethanes manufactures MDI-based polyurethane solutions used in a range of applications. Polyurethanes provide key benefits of efficiency, comfort and well-being. Polyurethanes also provide comfort and well-being in automotive seating, furniture, bedding, adhesive products, coatings and elastomers are used extensively throughout consumer and industrial applications. Performance Products manufactures products based on amines, carbonates, surfactants. End uses include agrochemicals, oil and gas and alternative solutions, home detergents and personal care products, adhesives and coatings, mining. In June 2007, it was announced that Huntsman had agreed to be acquired by Access Industries, owned by the billionaire Len Blavatnik, Huntsman shareholders would receive $25.25 a share from Access Industries chemical unit, Basell Holdings, based in Hoofddorp, Netherlands. Access would assume $3.7 billion of Huntsman debt, however, on July 12,2007 the agreement was terminated as Huntsman agreed to be bought by Apollo Management for $6.51 billion or $28 a share. Huntsman filed a suit against Apollo Management and its two partners in Texas after the group backed out of the deal to purchase the chemical company. The suit alleged fraud against Apollo Management as Huntsman believed that the group never intended to allow its Hexion Specialty Chemicals unit to buy Huntsman Corp. for $6.5 billion. Huntsman also claimed Apollo put forth a bid to prevent the Basell AF buyout as it would have threatened Hexions market share. Hexion stated Huntsmans declining financial position as the reason the deal was terminated, upon termination of the Hexion merger agreement, the Huntsman stock value dropped by almost 50%. In December 2008, Apollo and Hexion agreed to pay Huntsman $1 billion in return for Huntsman dropping all charges against them, a suit against the funding banks was settled in 2009 for $632 million in cash and $1.1 billion in loans to the Huntsman Corporation
23.
Royal Dutch Shell
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Royal Dutch Shell plc, commonly known as Shell, is a British–Dutch multinational oil and gas company headquartered in the Netherlands and incorporated in the United Kingdom. It is one of the six oil and gas supermajors and the sixth-largest company in the world measured by 2016 revenues. Shell was first in the 2013 Fortune Global 500 list of the worlds largest companies and it also has renewable energy activities in the form of biofuels and wind. Shell has operations in over 70 countries, produces around 3.7 million barrels of oil equivalent per day and has 44,000 service stations worldwide, as of 31 December 2014, Shell had total proved reserves of 13.7 billion barrels of oil equivalent. Shell Oil Company, its subsidiary in the United States, is one of its largest businesses. Shell holds 50% of Raízen, a joint venture with Cosan, which is the third-largest Brazil-based energy company by revenues, Shell was formed in 1907 through the amalgamation of the Royal Dutch Petroleum Company of the Netherlands and the Shell Transport and Trading Company of the United Kingdom. Shell first entered the industry in 1929. In 1970 Shell acquired the mining company Billiton, which it sold in 1994. In recent decades gas exploration and production has become an important part of Shells business. Shell acquired BG Group in 2016, making it the worlds largest producer of liquefied natural gas, Shell has a primary listing on the London Stock Exchange and is a constituent of the FTSE100 Index. It has secondary listings on Euronext Amsterdam and the New York Stock Exchange, as of January 2013, Shells largest shareholder was Capital Research Global Investors with 9. 85% ahead of BlackRock in second with 6. 89%. Shells logo, known as the pecten, is one of the most familiar commercial symbols in the world and it was a move largely driven by the need to compete globally with Standard Oil. The Shell Transport and Trading Company was a British company, founded in 1897 by Marcus Samuel, 1st Viscount Bearsted, and his brother Samuel Samuel. Their father had owned a company in Houndsditch, London. For various reasons, the new firm operated as a company, whereby the merging companies maintained their legal existence. The terms of the merger gave 60 percent ownership of the new group to the Dutch arm and 40 percent to the British, national patriotic sensibilities would not permit a full-scale merger or takeover of either of the two companies. The Dutch company, Koninklijke Nederlandsche Petroleum Maatschappij at The Hague, was in charge of production, the British Anglo-Saxon Petroleum Company was based in London, to direct the transport and storage of the products. During the First World War, Shell was the supplier of fuel to the British Expeditionary Force
24.
Composite material
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The individual components remain separate and distinct within the finished structure. The new material may be preferred for reasons, common examples include materials which are stronger, lighter. More recently, researchers have begun to actively include sensing, actuation, computation and communication into composites. The most advanced examples perform routinely on spacecraft and aircraft in demanding environments, the earliest man-made composite materials were straw and mud combined to form bricks for building construction. Ancient brick-making was documented by Egyptian tomb paintings, wattle and daub is one of the oldest man-made composite materials, at over 6000 years old. Concrete is also a material, and is used more than any other man-made material in the world. As of 2006, about 7.5 billion cubic metres of concrete are made each year—more than one metre for every person on Earth. 2181–2055 BC and was used for death masks Cob Mud Bricks, concrete was described by Vitruvius, writing around 25 BC in his Ten Books on Architecture, distinguished types of aggregate appropriate for the preparation of lime mortars. For structural mortars, he recommended pozzolana, which were volcanic sands from the beds of Pozzuoli brownish-yellow-gray in colour near Naples. Natural cement-stones, after burning, produced cements used in concretes from post-Roman times into the 20th century, the glass fiber is relatively strong and stiff, whereas the polymer is ductile. Thus the resulting fiberglass is relatively stiff, strong, flexible, concrete is the most common artificial composite material of all and typically consists of loose stones held with a matrix of cement. Concrete is a material, and will not compress or shatter even under quite a large compressive force. However, concrete cannot survive tensile loading, therefore, to give concrete the ability to resist being stretched, steel bars, which can resist high stretching forces, are often added to concrete to form reinforced concrete. Fibre-reinforced polymers or FRPs include carbon-fiber-reinforced polymer or CFRP, and glass-reinforced plastic or GRP, if classified by matrix then there are thermoplastic composites, short fiber thermoplastics, long fibre thermoplastics or long fibre-reinforced thermoplastics. There are numerous thermoset composites, including paper composite panels, many advanced thermoset polymer matrix systems usually incorporate aramid fibre and carbon fibre in an epoxy resin matrix. Shape memory polymer composites are high-performance composites, formulated using fibre or fabric reinforcement and they can also be reheated and reshaped repeatedly without losing their material properties. These composites are ideal for such as lightweight, rigid, deployable structures, rapid manufacturing. Although high strain composites exhibit many similarities to shape memory polymers, Composites can also use metal fibres reinforcing other metals, as in metal matrix composites or ceramic matrix composites, which includes bone, cermet and concrete
25.
Carbon fiber reinforced polymer
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Carbon fiber reinforced polymer, carbon fiber reinforced plastic or carbon fiber reinforced thermoplastic, is an extremely strong and light fiber-reinforced plastic which contains carbon fibers. The spelling fibre is common in British Commonwealth countries, the binding polymer is often a thermoset resin such as epoxy, but other thermoset or thermoplastic polymers, such as polyester, vinyl ester or nylon, are sometimes used. The composite may contain other fibers, such as an aramid, aluminium, ultra-high-molecular-weight polyethylene or glass fibers, the properties of the final CFRP product can also be affected by the type of additives introduced to the binding matrix. The most frequent additive is silica, but other such as rubber. The material is referred to as graphite-reinforced polymer or graphite fiber-reinforced polymer. In product advertisements, it is referred to simply as graphite fiber for short. In this case the composite consists of two parts, a matrix and a reinforcement, in CFRP the reinforcement is carbon fiber, which provides the strength. The matrix is usually a resin, such as epoxy. Because CFRP consists of two elements, the material properties depend on these two elements. The reinforcement will give the CFRP its strength and rigidity, measured by stress, unlike isotropic materials like steel and aluminum, CFRP has directional strength properties. The properties of CFRP depend on the layouts of the carbon fiber, the following equation, E c = V m E m + V f E f is valid for composite materials with the fibers oriented in the direction of the applied load. Typical epoxy-based CFRPs exhibit virtually no plasticity, with less than 0. 5% strain to failure, although CFRPs with epoxy have high strength and elastic modulus, the brittle fracture mechanics present unique challenges to engineers in failure detection since failure occurs catastrophically. As such, recent efforts to toughen CFRPs include modifying the existing epoxy material, One such material with high promise is PEEK, which exhibits an order of magnitude greater toughness with similar elastic modulus and tensile strength. However, PEEK is much more difficult to process and more expensive, despite its high initial strength-to-weight ratio, a design limitation of CFRP is its lack of a definable fatigue endurance limit. This means, theoretically, that stress cycle failure cannot be ruled out, environmental effects such as temperature and humidity can have profound effects on the polymer-based composites, including most CFRPs. While the carbon fibers themselves are not affected by the moisture diffusing into the material, the carbon fibers can cause galvanic corrosion when CRP parts are attached to aluminum. The primary element of CFRP is a filament, this is produced from a precursor polymer such as polyacrylonitrile, rayon. Precursor compositions and mechanical processes used during spinning filament yarns may vary among manufacturers, after drawing or spinning, the polymer filament yarns are then heated to drive off non-carbon atoms, producing the final carbon fiber
26.
Fiberglass
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Fiberglass is a type of fiber-reinforced plastic where the reinforcement fiber is specifically glass fiber. The glass fiber may be arranged, flattened into a sheet. The plastic matrix may be a polymer matrix – most often based on thermosetting polymers such as epoxy, polyester resin. The glass fibers are made of various types of glass depending upon the fiberglass use and these glasses all contain silica or silicate, with varying amounts of oxides of calcium, magnesium, and sometimes boron. To be used in fiberglass, glass fibers have to be made very low levels of defects. Fiberglass is a lightweight material and is used for many products. Although it is not as strong and stiff as composites based on fiber, it is less brittle. Its bulk strength and weight are also better than many metals, other common names for fiberglass are glass-reinforced plastic, glass-fiber reinforced plastic or GFK. Because glass fiber itself is referred to as fiberglass, the composite is also called fiberglass reinforced plastic. This article will adopt the convention that fiberglass refers to the glass fiber reinforced composite material. A patent for this method of producing glass wool was first applied for in 1933, Owens joined with the Corning company in 1935 and the method was adapted by Owens Corning to produce its patented fibreglas in 1936. Originally, fibreglas was a wool with fibers entrapping a great deal of gas, making it useful as an insulator. A suitable resin for combining the fibreglass with a plastic to produce a material was developed in 1936 by du Pont. The first ancestor of modern polyester resins is Cyanamids resin of 1942, peroxide curing systems were used by then. With the combination of fiberglass and resin the gas content of the material was replaced by plastic and this reduced the insulation properties to values typical of the plastic, but now for the first time the composite showed great strength and promise as a structural and building material. Confusingly, many glass fiber composites continued to be called fiberglass, ray Greene of Owens Corning is credited with producing the first composite boat in 1937, but did not proceed further at the time due to the brittle nature of the plastic used. In 1939 Russia was reported to have constructed a boat of plastic materials. The first car to have a body was a 1946 prototype of the Stout Scarab
27.
Polyester
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Polyester is a category of polymers that contain the ester functional group in their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate, polyesters include naturally occurring chemicals, such as in the cutin of plant cuticles, as well as synthetics through step-growth polymerization such as polybutyrate. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not and this material is used very widely in clothing. Depending on the structure, polyester can be a thermoplastic or thermoset. There are also polyester resins cured by hardeners, however, the most common polyesters are thermoplastics, industrial polyester fibers, yarns and ropes are used in car tire reinforcements, fabrics for conveyor belts, safety belts, coated fabrics and plastic reinforcements with high-energy absorption. Polyester fiber is used as cushioning and insulating material in pillows, comforters, Polyester fabrics are highly stain-resistant— in fact, the only class of dyes which can be used to alter the color of polyester fabric are what are known as disperse dyes. Polyester fibers are spun together with natural fibers to produce a cloth with blended properties. Cotton-polyester blends can be strong, wrinkle and tear-resistant, and reduce shrinking, synthetic fibers in polyester also create materials with water, wind and environmental resistance compared to plant-derived fibers. Disadvantages of cotton and polyester blends include being less breathable than cotton and they are also less fire resistant and can melt when ignited. Polyester blends have been renamed so as to suggest their similarity or even superiority to natural fibers. Polyesters are also used to make bottles, films, tarpaulin, canoes, liquid crystal displays, holograms, filters, dielectric film for capacitors, film insulation for wire, polyesters are widely used as a finish on high-quality wood products such as guitars, pianos and vehicle/yacht interiors. Thixotropic properties of spray-applicable polyesters make them ideal for use on open-grain timbers, as they can quickly fill wood grain, cured polyesters can be sanded and polished to a high-gloss, durable finish. Liquid crystalline polyesters are among the first industrially used liquid crystal polymers and they are used for their mechanical properties and heat-resistance. These traits are important in their application as an abradable seal in jet engines. Polyesters as thermoplastics may change shape after the application of heat, while combustible at high temperatures, polyesters tend to shrink away from flames and self-extinguish upon ignition. Polyester fibers have high tenacity and E-modulus as well as low water absorption and they are used in the liquid state as casting materials, in sheet molding compounds, as fiberglass laminating resins and in non-metallic auto-body fillers. They are also used as the polymer matrix in pre-pregs. Fiberglass-reinforced unsaturated polyesters find wide application in bodies of yachts and as parts of cars
28.
Resin
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In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. They are often mixtures of compounds, principally terpenes. Many plants, particularly woody plants, produce resin in response to injury, the resin acts as a bandage protecting the plant from invading insects and pathogens. Plants secrete resins and rosins for their protective benefits, the resin produced by most plants is composed mainly of terpenes and derivatives. Some resins also contain a proportion of resin acids. The individual components of resin can be separated by fractional distillation, rosins on the other hand are less volatile and consist, inter alia, of diterpenes. Amber is fossil resin from coniferous and other tree species, copal, kauri gum, dammar and other resins may also be found as subfossil deposits. Subfossil copal can be distinguished from genuine fossil amber because it becomes tacky when a drop of a solvent such as acetone or chloroform is placed on it, african copal and the kauri gum of New Zealand are also procured in a semi-fossil condition. Solidified resin from which the volatile terpene components have been removed by distillation is known as rosin, typical rosin is a transparent or translucent mass, with a vitreous fracture and a faintly yellow or brown colour, non-odorous or having only a slight turpentine odor and taste. Rosin is insoluble in water, mostly soluble in alcohol, essential oils, ether and hot fatty oils, and softens and melts under the influence of heat, rosin consists of a complex mixture of different substances including organic acids named the resin acids. These are closely related to the terpenes, and derive from them through partial oxidation, Resin acids can be dissolved in alkalis to form resin soaps, from which the purified resin acids are regenerated by treatment with acids. Examples of resin acids are abietic acid, C20H30O2, plicatic acid contained in cedar, and pimaric acid, C20H30O2, a constituent of galipot resin. Abietic acid can also be extracted from rosin by means of hot alcohol, it crystallizes in leaflets, pimaric acid closely resembles abietic acid into which it passes when distilled in a vacuum, it has been supposed to consist of three isomers. Rosin is obtained from pines and some plants, mostly conifers. Propolis, consisting largely of resins collected from such as poplars and conifers, is used by honey bees to seal gaps in their hives. Shellac and lacquer are examples of insect-derived resins, asphaltite and Utah resin are petroleum bitumens, not a product secreted by plants, although it was ultimately derived from plants. These were highly prized substances, and required as incense in religious rites. The word resin has been applied in the world to nearly any component of a liquid that will set into a hard lacquer or enamel-like finish
29.
Insulator (electricity)
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An electrical insulator is a material whose internal electric charges do not flow freely, very little electric current will flow through it under the influence of an electric field. This contrasts with other materials, semiconductors and conductors, which conduct electric current more easily, the property that distinguishes an insulator is its resistivity, insulators have higher resistivity than semiconductors or conductors. A perfect insulator does not exist, because even insulators contain small numbers of mobile charges which can carry current, in addition, all insulators become electrically conductive when a sufficiently large voltage is applied that the electric field tears electrons away from the atoms. This is known as the voltage of an insulator. Some materials such as glass, paper and Teflon, which have high resistivity, are good electrical insulators. Examples include rubber-like polymers and most plastics which can be thermoset or thermoplastic in nature, insulators are used in electrical equipment to support and separate electrical conductors without allowing current through themselves. An insulating material used in bulk to wrap electrical cables or other equipment is called insulation, the term insulator is also used more specifically to refer to insulating supports used to attach electric power distribution or transmission lines to utility poles and transmission towers. They support the weight of the suspended wires without allowing the current to flow through the tower to ground, electrical insulation is the absence of electrical conduction. Electronic band theory says that a charge flows if states are available into which electrons can be excited and this allows electrons to gain energy and thereby move through a conductor such as a metal. If no such states are available, the material is an insulator, most insulators have a large band gap. This occurs because the valence band containing the highest energy electrons is full, there is always some voltage that gives electrons enough energy to be excited into this band. Once this voltage is exceeded the material ceases being an insulator, however, it is usually accompanied by physical or chemical changes that permanently degrade the materials insulating properties. Materials that lack electron conduction are insulators if they lack other mobile charges as well, for example, if a liquid or gas contains ions, then the ions can be made to flow as an electric current, and the material is a conductor. Electrolytes and plasmas contain ions and act as conductors whether or not electron flow is involved, when subjected to a high enough voltage, insulators suffer from the phenomenon of electrical breakdown. These freed electrons and ions are in turn accelerated and strike other atoms, creating more charge carriers, rapidly the insulator becomes filled with mobile charge carriers, and its resistance drops to a low level. In a solid, the voltage is proportional to the band gap energy. The air in a region around a conductor can break down and ionise without a catastrophic increase in current. Even a vacuum can suffer a sort of breakdown, but in case the breakdown or vacuum arc involves charges ejected from the surface of metal electrodes rather than produced by the vacuum itself
30.
Silver
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Silver is a metallic element with symbol Ag and atomic number 47. The symbol Ag stems from Latin argentum, derived from the Greek ὰργὀς, a soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. The metal is found in the Earths crust in the pure, free form, as an alloy with gold and other metals. Most silver is produced as a byproduct of copper, gold, lead, Silver is more abundant than gold, but it is much less abundant as a native metal. Its purity is measured on a per mille basis, a 94%-pure alloy is described as 0.940 fine. As one of the seven metals of antiquity, silver has had a role in most human cultures. Silver has long valued as a precious metal. Silver metal is used in many premodern monetary systems in bullion coins, Silver is used in numerous applications other than currency, such as solar panels, water filtration, jewelry, ornaments, high-value tableware and utensils, and as an investment medium. Silver is used industrially in electrical contacts and conductors, in specialized mirrors, window coatings, Silver compounds are used in photographic film and X-rays. Dilute silver nitrate solutions and other compounds are used as disinfectants and microbiocides, added to bandages and wound-dressings, catheters. Silver is similar in its physical and chemical properties to its two neighbours in group 11 of the periodic table, copper and gold. This distinctive electron configuration, with an electron in the highest occupied s subshell over a filled d subshell. Silver is a soft, ductile and malleable transition metal. Silver crystallizes in a cubic lattice with bulk coordination number 12. Unlike metals with incomplete d-shells, metallic bonds in silver are lacking a covalent character and are relatively weak and this observation explains the low hardness and high ductility of single crystals of silver. Silver has a brilliant white metallic luster that can take a polish. Protected silver has greater optical reflectivity than aluminium at all wavelengths longer than ~450 nm, at wavelengths shorter than 450 nm, silvers reflectivity is inferior to that of aluminium and drops to zero near 310 nm. The electrical conductivity of silver is the greatest of all metals, greater even than copper, during World War II in the US,13540 tons of silver were used in electromagnets for enriching uranium, mainly because of the wartime shortage of copper
31.
Electrical resistivity and conductivity
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Electrical resistivity is an intrinsic property that quantifies how strongly a given material opposes the flow of electric current. A low resistivity indicates a material that allows the flow of electric current. Resistivity is commonly represented by the Greek letter ρ, the SI unit of electrical resistivity is the ohm-metre. Electrical conductivity or specific conductance is the reciprocal of electrical resistivity and it is commonly represented by the Greek letter σ, but κ or γ are also occasionally used. Its SI unit is siemens per metre and CGSE unit is reciprocal second, many resistors and conductors have a uniform cross section with a uniform flow of electric current, and are made of one material. All copper wires, irrespective of their shape and size, have approximately the same resistivity, every material has its own characteristic resistivity – for example, resistivity of rubber is far larger than coppers. If the pipes are the size and shape, the pipe full of sand has higher resistance to flow. Resistance, however, is not solely determined by the presence or absence of sand and it also depends on the length and width of the pipe, short or wide pipes have lower resistance than narrow or long pipes. The above equation can be transposed to get Pouillets law, R = ρ ℓ A, the resistance of a given material increases with length, but decreases with increasing cross-sectional area. From the above equations, resistivity has the SI unit ohm metre, the formula R = ρ ℓ / A can be used to intuitively understand the meaning of a resistivity value. For example, if A = 7000100000000000000♠1 m2 ℓ = 7000100000000000000♠1 m, Conductivity, σ, is defined as the inverse of resistivity, σ =1 ρ. Conductivity has SI units of siemens per metre, the above definition was specific to resistors or conductors with a uniform cross-section, where current flows uniformly through them. A more basic and general definition starts from the fact that a field inside a material makes electric current flow. Conductivity is the inverse, σ =1 ρ = J E, for example, rubber is a material with large ρ and small σ—because even a very large electric field in rubber makes almost no current flow through it. On the other hand, copper is a material with small ρ, according to elementary quantum mechanics, electrons in an atom do not take on arbitrary energy values. Rather, electrons only occupy discrete energy levels in an atom or crystal. When a large number of such allowed energy levels are spaced close together —i. e. have similar energies— we can talk about these energy levels together as an energy band. There can be many such bands in a material, depending on the atomic number
32.
Paint
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Paint is any liquid, liquefiable, or mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture to objects, Paint can be made or purchased in many colors—and in many different types, such as watercolor, synthetic, etc. Paint is typically stored, sold, and applied as a liquid, in 2001 and 2004, South African archeologists reported finds in Blombos Cave of a 100, 000-year-old human-made ochre-based mixture that could have been used like paint. Further excavation in the cave resulted in the 2011 report of a complete toolkit for grinding pigments. Cave paintings drawn with red or yellow ochre, hematite, manganese oxide, ancient colored walls at Dendera, Egypt, which were exposed for years to the elements, still possess their brilliant color, as vivid as when they were painted about 2,000 years ago. The Egyptians mixed their colors with a substance, and applied them separately from each other without any blending or mixture. They appear to have used six colors, white, black, blue, red, yellow and they first covered the area entirely with white, then traced the design in black, leaving out the lights of the ground color. They used minium for red, and generally of a dark tinge, pliny mentions some painted ceilings in his day in the town of Ardea, which had been done prior to the foundation of Rome. He expresses great surprise and admiration at their freshness, after the lapse of so many centuries, Paint was made with the yolk of eggs and therefore, the substance would harden and adhere to the surface it was applied to. Pigment was made from plants, sand, and different soils, Most paints used either oil or water as a base. The process was done by hand by the painters and exposed them to lead poisoning due to the white-lead powder, in 1718, Marshall Smith invented a Machine or Engine for the Grinding of Colours in England. It is not known precisely how it operated, but it was a device that increased the efficiency of pigment grinding dramatically. By the proper onset of the Industrial Revolution, paint was being ground in steam-powered mills, interior house painting increasingly became the norm as the 19th century progressed, both for decorative reasons and because the paint was effective in preventing the walls rotting from damp. Linseed oil was also used as an inexpensive binder. In 1866, Sherwin-Williams in the United States opened as a large paint-maker and it was not until the stimulus of World War II created a shortage of linseed oil in the supply market that artificial resins, or alkyds, were invented. Cheap and easy to make, they held the color well. The vehicle is composed of the binder, or, if it is necessary to thin the binder with a diluent like solvent or water, it is the combination of binder + diluent. In this case, once the paint has dried or cured very nearly all of the diluent has evaporated, thus, an important quantity in coatings formulation is the vehicle solids, sometimes called the resin solids of the formula
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Fusion bonded epoxy coating
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FBE coatings are thermoset polymer coatings. They come under the category of protective coatings in paints and coating nomenclature, the name fusion-bond epoxy is due to resin cross-linking and the application method, which is different from a conventional paint. The resin and hardener components in the dry powder FBE stock remain unreacted at normal storage conditions, at typical coating application temperatures, usually in the range of 180 to 250 °C, the contents of the powder melt and transform to a liquid form. The liquid FBE film wets and flows onto the surface on which it is applied. This process is known as “fusion bonding”, the chemical cross-linking reaction taking place in this case is irreversible. Once the curing takes place, the coating cannot be returned to its form by any means. Application of further heating will not “melt” the coating and thus it is known as a “thermoset” coating. The worlds leading FBE manufacturers are Valspar, SolEpoxy, KCC Corporation, Jotun Powder Coatings, Sherwin-Williams, 3M, Axalta Coating Systems, Akzo Nobel, BASF, since their introduction as a protective coating in early 1960s, FBE coating formulations had gone through vast improvements and developments. Today, various types of FBE coatings, which are made to meet various requirements are available. FBEs are available as stand-alone coatings as well as a part in multi-layers, FBE coatings with different properties are available to suit coating application on the main body of pipe, internal surfaces, girth welds as well as on fittings. Essential components of a coating are Resin. The resin and hardener part together is known as the Binder, as the name indicates, in Fusion bonded epoxy coatings the resin part is an epoxy type resin. “Epoxy” or “Oxirane” structure contains a three membered cyclic ring — one oxygen atom connected to two carbon atoms - in the resin molecule and this part is the most reactive group in the epoxy resins. Most commonly used FBE resins are derivatives of bisphenol A and epichlorohydrin, however, other types of resins are also commonly used in FBE formulations to achieve various properties, combinations or additions. Resins are also available in various lengths, to provide unique properties to the final coating. The second most important part of FBE coatings is the agent or hardener. Curing agents react either with the ring or with the hydroxyl groups. Various types of curing agents, used in FBE manufacture, include dicyandiamide, aromatic amines, aliphatic diamines, the selected curing agent determines the nature of the final FBE product — its cross linking density, chemical resistance, brittleness, flexibility etc
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Rebar
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Rebars surface is often patterned to form a better bond with the concrete. Rebar has been used in construction since at least the 15th century, more recently, during the 18th century, rebar was used to form the carcass of the Leaning Tower of Nevyansk in Russia, built on the orders of the industrialist Akinfiy Demidov. The cast iron used for the rebar was of high quality, the carcass of the tower was connected to its cast iron tented roof, crowned with one of the first known lightning rods. More recently these techniques have been refined by embedding the steel bars in the concrete, concrete is a material that is very strong in compression, but relatively weak in tension. To compensate for this imbalance in concretes behavior, rebar is cast into it to carry the tensile loads, rebar is also employed to confer resistance to concentrated loads by providing enough localized resistance and stiffness for a load to spread through a wider area. Rebar may also be used to other steel bars in the correct position to accommodate their loads. External steel tie bars can constrain and reinforce masonry structures, as illustrated by the Nevyansk Tower or ancient structures in Rome, masonry structures and the mortar holding them together have similar properties to concrete and also have a limited ability to carry tensile loads. Some standard masonry units like blocks and bricks are made with voids to accommodate rebar and this combination is known as reinforced masonry. Steel has a thermal expansion coefficient nearly equal to that of modern concrete, if this were not so, it would cause problems through additional longitudinal and perpendicular stresses at temperatures different from the temperature of the setting. To prevent such a failure, rebar is either deeply embedded into adjacent structural members, or bent and hooked at the ends to lock it around the concrete and other rebar. This first approach increases the friction locking the bar into place, common rebar is made of unfinished tempered steel, making it susceptible to rusting. Normally the concrete cover is able to provide a pH value higher than 12 avoiding the corrosion reaction, too little concrete cover can compromise this guard through carbonation from the surface, and salt penetration. Too much concrete cover can cause bigger crack widths which also compromises the local guard and this phenomenon is known as oxide jacking. This is a problem where the concrete is exposed to salt water, as in bridges where salt is applied to roadways in winter. Even damaged bars have shown better performance than uncoated reinforcing bars, though issues from debonding of the coating from the bars. These bars are used in over 70,000 bridge decks in the USA, fiber-reinforced polymer rebar is also used in high-corrosion environments. It is available in forms, such as spirals for reinforcing columns, common rods. Most commercially available rebar is made from glass fibre reinforced thermoset resins
35.
Primer (paint)
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A primer or undercoat is a preparatory coating put on materials before painting. Priming ensures better adhesion of paint to the surface, increases paint durability, 20%-30% synthetic resin, 60%-80% solvent and 2%-5% additive agent. Some primer contains polyethylene, for better durability, primer is a paint product that allows finishing paint to adhere much better than if it were used alone. For this purpose, primer is designed to adhere to surfaces, because primers do not need to be engineered to have durable, finished surfaces, they can instead be engineered to have improved filling and binding properties with the material underneath. In practice, primer is used when painting many kinds of porous materials, such as concrete. Priming is mandatory if the material is not water resistant and will be exposed to the elements, priming gypsum board is also standard practice with new construction because it seals the wall and aids in preventing mold. Primers can also be used for dirty surfaces that, for reason, cannot be cleaned. Primers can usually be tinted to a match with the color of the finishing paint. If the finishing paint is a color, tinting the primer can reduce the number of layers of finishing paint that are necessary for good uniformity across the painted surface. There may be a time frame within which a topcoat should be applied over the primer after the primer dries. Depending on the primer, the coat of paint should be applied as quickly as 24 hours or as long as two weeks. Painting after the suggested timeframe may cause performance issues depending on the specific situation, supposedly, you want to apply the finish coat of paint before the primer fully cures on a molecular level. Doing this allows maximum adhesion/bonding of the topcoat to the primer, if topcoating after the suggested timeframe, consider using a self priming topcoat. For definitive answers on recommended repainting timeframe, check the primer label/website, recoat timeframe is most likely a more critical factor in exterior application because of the more extreme climatic exposure. Using a primer on wood before painting is important for several reasons, first of all, wood is very porous and will absorb the solvent from paint, drying the paint prematurely. Because most paints undergo chemical reactions during the process of curing, a layer of primer will help the paint to undergo its proper, complete curing cycle. Secondly, without a primer, several layers of paint can be necessary to completely obscure the wood grain, lastly, if wood is exposed to moisture, a thin layer of paint will still be water permeable. The end result will be warped parts, mildew, and dry rot, primer adds to the waterproofing effect of the paint
36.
Corrosion
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Corrosion is a natural process, which converts a refined metal to a more chemically-stable form, such as its oxide, hydroxide, or sulfide. It is the destruction of materials by chemical and/or electrochemical reaction with their environment. Corrosion engineering is the dedicated to controlling and stopping corrosion. In the most common use of the word, this means electrochemical oxidation of metal in reaction with an oxidant such as oxygen or sulfur, rusting, the formation of iron oxides, is a well-known example of electrochemical corrosion. This type of damage typically produces oxide or salt of the original metal, corrosion can also occur in materials other than metals, such as ceramics or polymers, although in this context, the term degradation is more common. Corrosion degrades the useful properties of materials and structures including strength, appearance and permeability to liquids, many structural alloys corrode merely from exposure to moisture in air, but the process can be strongly affected by exposure to certain substances. Corrosion can be concentrated locally to form a pit or crack, because corrosion is a diffusion-controlled process, it occurs on exposed surfaces. As a result, methods to reduce the activity of the surface, such as passivation and chromate conversion. However, some corrosion mechanisms are less visible and less predictable, in a galvanic couple, the more active metal corrodes at an accelerated rate and the more noble metal corrodes at a slower rate. When immersed separately, each metal corrodes at its own rate, what type of metal to use is readily determined by following the galvanic series. For example, zinc is used as a sacrificial anode for steel structures. Galvanic corrosion is of major interest to the industry and also anywhere water contacts pipes or metal structures. Factors such as size of anode, types of metal. The surface area ratio of the anode and cathode directly affects the corrosion rates of the materials, galvanic corrosion is often prevented by the use of sacrificial anodes. In any given environment, one metal will be more noble or more active than others. Two metals in electrical contact share the same electrons, so that the tug-of-war at each surface is analogous to competition for free electrons between the two materials. Using the electrolyte as a host for the flow of ions in the same direction, the resulting mass flow or electric current can be measured to establish a hierarchy of materials in the medium of interest. This hierarchy is called a series and is useful in predicting and understanding corrosion
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Acid
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An acid is a molecule or ion capable of donating a hydron, or, alternatively, capable of forming a covalent bond with an electron pair. The first category of acids is the donors or Brønsted acids. In the special case of solutions, proton donors form the hydronium ion H3O+ and are known as Arrhenius acids. Brønsted and Lowry generalized the Arrhenius theory to include non-aqueous solvents, acids form aqueous solutions with a sour taste, can turn blue litmus red, and react with bases and certain metals to form salts. The word acid is derived from the Latin acidus/acēre meaning sour, an aqueous solution of an acid has a pH less than 7 and is colloquially also referred to as acid, while the strict definition refers only to the solute. A lower pH means a higher acidity, and thus a higher concentration of hydrogen ions in the solution. Chemicals or substances having the property of an acid are said to be acidic, common aqueous acids include hydrochloric acid, acetic acid, sulfuric acid, and citric acid. As these examples show, acids can be solutions or pure substances, strong acids and some concentrated weak acids are corrosive, but there are exceptions such as carboranes and boric acid. The second category of acids are Lewis acids, which form a covalent bond with an electron pair, however, hydrogen chloride, acetic acid, and most other Brønsted-Lowry acids cannot form a covalent bond with an electron pair and are therefore not Lewis acids. Conversely, many Lewis acids are not Arrhenius or Brønsted-Lowry acids, in modern terminology, an acid is implicitly a Brønsted acid and not a Lewis acid, since chemists almost always refer to a Lewis acid explicitly as a Lewis acid. Modern definitions are concerned with the chemical reactions common to all acids. Most acids encountered in life are aqueous solutions, or can be dissolved in water, so the Arrhenius. The Brønsted-Lowry definition is the most widely used definition, unless otherwise specified, hydronium ions are acids according to all three definitions. Interestingly, although alcohols and amines can be Brønsted-Lowry acids, they can function as Lewis bases due to the lone pairs of electrons on their oxygen and nitrogen atoms. The Swedish chemist Svante Arrhenius attributed the properties of acidity to hydrogen ions or protons in 1884, an Arrhenius acid is a substance that, when added to water, increases the concentration of H+ ions in the water. Thus, an Arrhenius acid can also be described as a substance that increases the concentration of ions when added to water. Examples include molecular substances such as HCl and acetic acid, an Arrhenius base, on the other hand, is a substance which increases the concentration of hydroxide ions when dissolved in water. Thus, an Arrhenius acid could also be said to be one that decreases hydroxide concentration, in an acidic solution, the concentration of hydronium ions is greater than 10−7 moles per liter
38.
Terrazzo
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Terrazzo is a composite material, poured in place or precast, which is used for floor and wall treatments. It consists of chips of marble, quartz, granite, glass, or other material, poured with a cementitious binder, polymeric. Metal strips divide sections, or changes in color or material in a pattern, additional chips may be sprinkled atop the mix before it sets. After it is cured it is ground and polished smooth or otherwise finished to produce a textured surface. Terrazzo was created by Venetian construction workers as a low cost flooring material to surface the patios around their living quarters. Archaeologists have adopted the term terrazzo to describe the floors of early buildings in Western Asia constructed of burnt lime and clay, colored red with ochre. The embedded crushed limestone gives it a slightly mottled appearance, the use of fire to produce burnt lime, which was also used for the hafting of implements, predates production of fired pottery by almost a thousand years. In the early Neolithic settlement of Cayönü in eastern Turkey ca.90 m² of terrazzo floors have been uncovered, the floors of the PPN B settlement of Nevali Cori measure about 80 m². They are 15 cm thick, and contain about 10–15% lime and these floors are almost impenetrable to moisture and very durable, but their construction involved a high input of energy. Gourdin and Kingery estimate that the production of any amount of lime requires about five times that amount of wood. Recent experiments by Affonso and Pernicka have shown only twice the amount is needed. Other sites with terrazzo floors include Nevali Cori, Göbekli Tepe, Jericho, terrazzo artisans create walls, floors, patios, and panels by exposing marble chips and other fine aggregates on the surface of finished concrete or epoxy-resin. Much of the work of terrazzo workers is similar to that of cement masons. Marble-chip, cementitious terrazzo requires three layers of materials, first, cement masons or terrazzo workers build a solid, level concrete foundation that is three to four inches deep. After the forms are removed from the foundation, workers add a layer of sandy concrete. Before this layer sets, terrazzo workers partially embed metal divider strips in the concrete wherever there is to be a joint or change of color in the terrazzo. For the final layer, terrazzo workers blend and place each of the panels a fine marble chip mixture that may be color-pigmented. While the mixture is wet, workers toss additional marble chips of various colors into each panel
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