Wool is the textile fiber obtained from sheep and other animals, including cashmere and mohair from goats, qiviut from muskoxen, from hide and fur clothing from bison, angora from rabbits, other types of wool from camelids. Wool consists of protein together with a few percent lipids. In this regard it is chemically quite distinct from the more dominant textile, cellulose. Wool is produced by follicles; these follicles are located in the upper layer of the skin called the epidermis and push down into the second skin layer called the dermis as the wool fibers grow. Follicles can be classed as either secondary follicles. Primary follicles produce three types of fiber: kemp, medullated fibers, true wool fibers. Secondary follicles only produce true wool fibers. Medullated fibers share nearly identical characteristics to hair and are long but lack crimp and elasticity. Kemp fibers are coarse and shed out. Wool's scaling and crimp make it easier to spin the fleece by helping the individual fibers attach to each other, so they stay together.
Because of the crimp, wool fabrics have greater bulk than other textiles, they hold air, which causes the fabric to retain heat. Wool has a high specific thermal resistance, so it impedes heat transfer in general; this effect has benefited desert peoples, as Tuaregs use wool clothes for insulation. Felting of wool occurs upon hammering or other mechanical agitation as the microscopic barbs on the surface of wool fibers hook together. Wool has several qualities that distinguish it from hair/fur: it is crimped and elastic; the amount of crimp corresponds to the fineness of the wool fibers. A fine wool like Merino may have up to 100 crimps per inch, while coarser wool like karakul may have as few as one or two. In contrast, hair has little if any scale and no crimp, little ability to bind into yarn. On sheep, the hair part of the fleece is called kemp; the relative amounts of kemp to wool vary from breed to breed and make some fleeces more desirable for spinning, felting, or carding into batts for quilts or other insulating products, including the famous tweed cloth of Scotland.
Wool fibers absorb moisture, but are not hollow. Wool can absorb one-third of its own weight in water. Wool absorbs sound like many other fabrics, it is a creamy white color, although some breeds of sheep produce natural colors, such as black, brown and random mixes. Wool ignites at a higher temperature than some synthetic fibers, it has a lower rate of flame spread, a lower rate of heat release, a lower heat of combustion, does not melt or drip. Wool carpets are specified for high safety environments, such as trains and aircraft. Wool is specified for garments for firefighters and others in occupations where they are exposed to the likelihood of fire. Wool causes an allergic reaction in some people. Sheep shearing is the process. After shearing, the wool is separated into four main categories: fleece, broken and locks; the quality of fleeces is determined by a technique known as wool classing, whereby a qualified person, called a wool classer, groups wools of similar gradings together to maximize the return for the farmer or sheep owner.
In Australia before being auctioned, all Merino fleece wool is objectively measured for micron, staple length, staple strength, sometimes color and comfort factor. Wool straight off a sheep, known as "greasy wool" or "wool in the grease", contains a high level of valuable lanolin, as well as the sheep's dead skin and sweat residue, also contains pesticides and vegetable matter from the animal's environment. Before the wool can be used for commercial purposes, it must be scoured, a process of cleaning the greasy wool. Scouring may be as simple as a bath in warm water or as complicated as an industrial process using detergent and alkali in specialized equipment. In north west England, special potash pits were constructed to produce potash used in the manufacture of a soft soap for scouring locally produced white wool. In commercial wool, vegetable matter is removed by chemical carbonization. In less-processed wools, vegetable matter may be removed by hand and some of the lanolin left intact through the use of gentler detergents.
This semigrease wool can be worked into yarn and knitted into water-resistant mittens or sweaters, such as those of the Aran Island fishermen. Lanolin removed from wool is used in cosmetic products, such as hand creams. Raw wool has many impurities; the sheep's body yields many types of wool with differing strengths, length of staple and impurities. The raw wool is processed into'top'.'Worsted top' requires strong straight and parallel fibres. The quality of wool is determined by its fiber diameter, yield and staple strength. Fiber diameter is the single most important wool characteristic determining price. Merino wool is 3–5 inches in length and is fine; the finest and most valuable wool comes from Merino hoggets. Wool taken from sheep produced for meat is more coarse, has fibers 1.5 to 6 in in length. Damage or breaks in the wool can occur if the sheep is stressed whil
A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the nuclei, can be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur; the substance involved in a chemical reaction are called reactants or reagents. Chemical reactions are characterized by a chemical change, they yield one or more products, which have properties different from the reactants. Reactions consist of a sequence of individual sub-steps, the so-called elementary reactions, the information on the precise course of action is part of the reaction mechanism. Chemical reactions are described with chemical equations, which symbolically present the starting materials, end products, sometimes intermediate products and reaction conditions.
Chemical reactions happen at a characteristic reaction rate at a given temperature and chemical concentration. Reaction rates increase with increasing temperature because there is more thermal energy available to reach the activation energy necessary for breaking bonds between atoms. Reactions may proceed in the forward or reverse direction until they go to completion or reach equilibrium. Reactions that proceed in the forward direction to approach equilibrium are described as spontaneous, requiring no input of free energy to go forward. Non-spontaneous reactions require input of free energy to go forward. Different chemical reactions are used in combinations during chemical synthesis in order to obtain a desired product. In biochemistry, a consecutive series of chemical reactions form metabolic pathways; these reactions are catalyzed by protein enzymes. Enzymes increase the rates of biochemical reactions, so that metabolic syntheses and decompositions impossible under ordinary conditions can occur at the temperatures and concentrations present within a cell.
The general concept of a chemical reaction has been extended to reactions between entities smaller than atoms, including nuclear reactions, radioactive decays, reactions between elementary particles, as described by quantum field theory. Chemical reactions such as combustion in fire and the reduction of ores to metals were known since antiquity. Initial theories of transformation of materials were developed by Greek philosophers, such as the Four-Element Theory of Empedocles stating that any substance is composed of the four basic elements – fire, water and earth. In the Middle Ages, chemical transformations were studied by Alchemists, they attempted, in particular, to convert lead into gold, for which purpose they used reactions of lead and lead-copper alloys with sulfur. The production of chemical substances that do not occur in nature has long been tried, such as the synthesis of sulfuric and nitric acids attributed to the controversial alchemist Jābir ibn Hayyān; the process involved heating of sulfate and nitrate minerals such as copper sulfate and saltpeter.
In the 17th century, Johann Rudolph Glauber produced hydrochloric acid and sodium sulfate by reacting sulfuric acid and sodium chloride. With the development of the lead chamber process in 1746 and the Leblanc process, allowing large-scale production of sulfuric acid and sodium carbonate chemical reactions became implemented into the industry. Further optimization of sulfuric acid technology resulted in the contact process in the 1880s, the Haber process was developed in 1909–1910 for ammonia synthesis. From the 16th century, researchers including Jan Baptist van Helmont, Robert Boyle, Isaac Newton tried to establish theories of the experimentally observed chemical transformations; the phlogiston theory was proposed in 1667 by Johann Joachim Becher. It postulated the existence of a fire-like element called "phlogiston", contained within combustible bodies and released during combustion; this proved to be false in 1785 by Antoine Lavoisier who found the correct explanation of the combustion as reaction with oxygen from the air.
Joseph Louis Gay-Lussac recognized in 1808 that gases always react in a certain relationship with each other. Based on this idea and the atomic theory of John Dalton, Joseph Proust had developed the law of definite proportions, which resulted in the concepts of stoichiometry and chemical equations. Regarding the organic chemistry, it was long believed that compounds obtained from living organisms were too complex to be obtained synthetically. According to the concept of vitalism, organic matter was endowed with a "vital force" and distinguished from inorganic materials; this separation was ended however by the synthesis of urea from inorganic precursors by Friedrich Wöhler in 1828. Other chemists who brought major contributions to organic chemistry include Alexander William Williamson with his synthesis of ethers and Christopher Kelk Ingold, among many discoveries, established the mechanisms of substitution reactions. Chemical equations are used to graphically illustrate chemical reactions, they consist of chemical or structural formulas of the reactants on the left and those of the products on the right.
They are separated by an arrow which indicates the type of the reaction.
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is applied in an aqueous solution, may require a mordant to improve the fastness of the dye on the fiber. Both dyes and pigments are colored. Dyes are soluble in water whereas pigments are insoluble; some dyes can be rendered insoluble with the addition of salt to produce a lake pigment. The majority of natural dyes are derived from plant sources: roots, bark and wood, lichens. Most dyes are synthetic, i.e. are man-made from petrochemicals. Other than pigmentation, they have a range of applications including organic dye lasers, optical media and camera sensors. Textile dyeing dates back to the Neolithic period. Throughout history, people have dyed their textiles using common, locally available materials. Scarce dyestuffs that produced brilliant and permanent colors such as the natural invertebrate dyes Tyrian purple and crimson kermes were prized luxury items in the ancient and medieval world.
Plant-based dyes such as woad, indigo and madder were important trade goods in the economies of Asia and Europe. Across Asia and Africa, patterned fabrics were produced using resist dyeing techniques to control the absorption of color in piece-dyed cloth. Dyes from the New World such as cochineal and logwood were brought to Europe by the Spanish treasure fleets, the dyestuffs of Europe were carried by colonists to America. Dyed flax fibers have been found in the Republic of Georgia in a prehistoric cave dated to 36,000 BP. Archaeological evidence shows that in India and Phoenicia, dyeing has been carried out for over 5,000 years. Early dyes were obtained from animal, vegetable or mineral sources, with no to little processing. By far the greatest source of dyes has been from the plant kingdom, notably roots, bark and wood, only few of which are used on a commercial scale; the first synthetic dye, was discovered serendipitously by William Henry Perkin in 1856. The discovery of mauveine started a surge in organic chemistry in general.
Other aniline dyes followed, such as fuchsine and induline. Many thousands of synthetic dyes have since been prepared. Dyes are classified according to their chemical properties. Acid dyes are water-soluble anionic dyes that are applied to fibers such as silk, wool and modified acrylic fibers using neutral to acid dye baths. Attachment to the fiber is attributed, at least to salt formation between anionic groups in the dyes and cationic groups in the fiber. Acid dyes are not substantive to cellulosic fibers. Most synthetic food colors fall in this category. Examples of acid dye are Acid red 88, etc.. Basic dyes are water-soluble cationic dyes that are applied to acrylic fibers, but find some use for wool and silk. Acetic acid is added to the dye bath to help the uptake of the dye onto the fiber. Basic dyes are used in the coloration of paper. Direct or substantive dyeing is carried out in a neutral or alkaline dye bath, at or near boiling point, with the addition of either sodium chloride or sodium sulfate or sodium carbonate.
Direct dyes are used on cotton, leather, wool and nylon. They are used as pH indicators and as biological stains. Mordant dyes require a mordant, which improves the fastness of the dye against water and perspiration; the choice of mordant is important as different mordants can change the final color significantly. Most natural dyes are mordant dyes and there is therefore a large literature base describing dyeing techniques; the most important mordant dyes are chrome dyes, used for wool. The mordant potassium dichromate is applied as an after-treatment, it is important to note that many mordants those in the heavy metal category, can be hazardous to health and extreme care must be taken in using them. Vat dyes are insoluble in water and incapable of dyeing fibres directly. However, reduction in alkaline liquor produces the water-soluble alkali metal salt of the dye; this form is colorless, in which case it is referred to as a Leuco dye, has an affinity for the textile fibre. Subsequent oxidation reforms the original insoluble dye.
The color of denim is due to the original vat dye. Reactive dyes utilize a chromophore attached to a substituent, capable of directly reacting with the fiber substrate; the covalent bonds that attach reactive dye to natural fibers make them among the most permanent of dyes. "Cold" reactive dyes, such as Procion MX, Cibacron F, Drimarene K, are easy to use because the dye can be applied at room temperature. Reactive dyes are by far the best choice for dyeing cotton and other cellulose fibers at home or in the art studio. Disperse dyes were developed for the dyeing of cellulose acetate, are water-insoluble; the dyes are finely ground in the presence of a dispersing agent and sold as a paste, or spray-dried and sold as a powder. Their main use is to dye polyester, but they can be used to dye nylon, cellulose triacetate, acrylic fibers. In some cases, a dyeing temperature of 130 °C is required, a pressurized dyebath is used; the fine particle size gives a large surface area that aids dissolution to allow uptake by the fiber.
The dyeing rate can be influenced by the choice of dispersing agent used during the grinding. Azoic dyeing is a technique in which an insoluble Azo dye is produced directly
Colour fastness is a term—used in the dyeing of textile materials—that characterizes a material's colour's resistance to fading or running. The term is used in the context of clothes. In general, clothing should be tested for colorfastness before using bleach or other cleaning products. Light fastness, wash fastness, rub fastness are the main forms of colour fastness that are standardized; the light fastness of textile dye is categorized from one to eight and the wash fastness from one to five, with a higher the number indicating better fastness. "Color Fastness" "Different Color Fastness Tests" Colorfast
Sodium dithionite is a white crystalline powder with a weak sulfurous odor. Although it is stable in the absence of air, it decomposes in acid solutions. Raman spectroscopy and single-crystal X-ray diffraction studies reveal that the geometry of the dithionite anion is flexible; the dithionite dianion has C2 symmetry, with eclipsed with a 16° O-S-S-O torsional angle. In the dihydrated form, the dithionite anion has a shorter S-S bond length and a gauche 56° O-S-S-O torsional angle. A weak S-S bond is indicated by the S-S distance of 239 pm; because this bond is fragile, the dithionite anion dissociates in solution into the − radical anion, as has been confirmed by EPR spectroscopy. It is observed that 35S undergoes rapid exchange between S2O42− and SO2 in neutral or acidic solution, consistent with the weak S-S bond in the anion. Sodium dithionite is produced industrially by reduction of sulfur dioxide. Several methods are employed, including reduction with zinc powder, sodium borohydride, formate.
300,000 tons were produced in 1990. Sodium dithionite is stable when dry, but aqueous solutions deteriorate due to the following reaction: 2 S2O42− + H2O → S2O32− + 2 HSO3−This behavior is consistent with the instability of dithionous acid. Thus, solutions of sodium dithionite cannot be stored for a long period of time. Anhydrous sodium dithionite decomposes to sodium sulfur dioxide above 90 °C in the air. In absence of air, it decomposes above 150 °C to sodium sulfite, sodium thiosulfate, sulfur dioxide and trace amount of sulfur. Sodium dithionite is a reducing agent. At pH=7, the potential is -0.66 V vs NHE. Redox occurs with formation of sulfite: S2O42- + 2 H2O → 2 HSO3− + 2 e− + 2 H+Sodium dithionite reacts with oxygen: Na2S2O4 + O2 + H2O → NaHSO4 + NaHSO3These reactions exhibit complex pH-dependent equilibria involving bisulfite and sulfur dioxide. In the presence of aldehydes, sodium dithionite reacts either to form α-hydroxy-sulfinates at room temperature or to reduce the aldehyde to the corresponding alcohol above a temperature of 85 °C.
Some ketones are reduced under similar conditions. This compound is a water-soluble salt, can be used as a reducing agent in aqueous solutions, it is used as such in some industrial dyeing processes those involving sulfur dyes and vat dyes, where an otherwise water-insoluble dye can be reduced into a water-soluble alkali metal salt. The reduction properties of sodium dithionite eliminate excess dye, residual oxide, unintended pigments, thereby improving overall colour quality. Sodium dithionite can be used for water treatment, gas purification and stripping, it can be used in industrial processes as a sulfonating agent or a sodium ion source. In addition to the textile industry, this compound is used in industries concerned with leather, polymers and many others, its wide use is attributable to its low toxicity LD50 at 5 g/kg, hence its wide range of applications. It is used as decolourising agent in organic reactions. Sodium dithionite is used in physiology experiments as a means of lowering solutions' redox potential.
Potassium ferricyanide is used as an oxidizing chemical in such experiments. In addition, sodium dithionite is used in soil chemistry experiments to determine the amount of iron, not incorporated in primary silicate minerals. Hence, iron extracted by sodium dithionite is referred to as "free iron." The strong affinity of the dithionite ion for bi- and trivalent metal cations allows it to enhance the solubility of iron, therefore dithionite is a useful chelating agent. Sodium dithionite has been used in chemical enhanced oil recovery to stabilize polyacrylamide polymers against radical degradation in the presence of iron, it has been used in environmental applications to propagate a low Eh front in the subsurface in order to reduce components such as chromium. It can be used as a developer, but it is a uncommon choice, it is prone to reduce film speed and, if improperly used fogs the image. Aqueous solutions of sodium dithionite were once used to produce "Fieser's solution' for the removal of oxygen from a gas stream.
Pyrithione can be prepared in a two-step synthesis from 2-bromopyridine by oxidation to the N-oxide with a suitable peracid followed by substitution using sodium dithionite to introduce the thiol functional group. Dithionite Sodium dithionite - ipcs inchem
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus Gossypium in the mallow family Malvaceae. The fiber is pure cellulose. Under natural conditions, the cotton bolls will increase the dispersal of the seeds; the plant is a shrub native to tropical and subtropical regions around the world, including the Americas, Africa and India. The greatest diversity of wild cotton species is found followed by Australia and Africa. Cotton was independently domesticated in the New Worlds; the fiber is most spun into yarn or thread and used to make a soft, breathable textile. The use of cotton for fabric is known to date to prehistoric times. Although cultivated since antiquity, it was the invention of the cotton gin that lowered the cost of production that led to its widespread use, it is the most used natural fiber cloth in clothing today. Current estimates for world production are about 25 million tonnes or 110 million bales annually, accounting for 2.5% of the world's arable land.
China is the world's largest producer of cotton. The United States has been the largest exporter for many years. In the United States, cotton is measured in bales, which measure 0.48 cubic meters and weigh 226.8 kilograms. There are four commercially grown species of cotton, all domesticated in antiquity: Gossypium hirsutum – upland cotton, native to Central America, the Caribbean and southern Florida Gossypium barbadense – known as extra-long staple cotton, native to tropical South America Gossypium arboreum – tree cotton, native to India and Pakistan Gossypium herbaceum – Levant cotton, native to southern Africa and the Arabian Peninsula The two New World cotton species account for the vast majority of modern cotton production, but the two Old World species were used before the 1900s. While cotton fibers occur in colors of white, brown and green, fears of contaminating the genetics of white cotton have led many cotton-growing locations to ban the growing of colored cotton varieties; the word "cotton" has Arabic origins, derived from the Arabic word قطن.
This was the usual word for cotton in medieval Arabic. The word entered the Romance languages in the mid-12th century, English a century later. Cotton fabric was known to the ancient Romans as an import but cotton was rare in the Romance-speaking lands until imports from the Arabic-speaking lands in the medieval era at transformatively lower prices; the earliest evidence of cotton use in the Indian subcontinent has been found at the site of Mehrgarh and Rakhigarhi where cotton threads have been found preserved in copper beads. Cotton cultivation in the region is dated to the Indus Valley Civilization, which covered parts of modern eastern Pakistan and northwestern India between 3300 and 1300 BC; the Indus cotton industry was well-developed and some methods used in cotton spinning and fabrication continued to be used until the industrialization of India. Between 2000 and 1000 BC cotton became widespread across much of India. For example, it has been found at the site of Hallus in Karnataka dating from around 1000 BC.
Cotton bolls discovered in a cave near Tehuacán, have been dated to as early as 5500 BC, but this date has been challenged. More securely dated is the domestication of Gossypium hirsutum in Mexico between around 3400 and 2300 BC. In Peru, cultivation of the indigenous cotton species Gossypium barbadense has been dated, from a find in Ancon, to c. 4200 BC, was the backbone of the development of coastal cultures such as the Norte Chico and Nazca. Cotton was grown upriver, made into nets, traded with fishing villages along the coast for large supplies of fish; the Spanish who came to Mexico and Peru in the early 16th century found the people growing cotton and wearing clothing made of it. The Greeks and the Arabs were not familiar with cotton until the Wars of Alexander the Great, as his contemporary Megasthenes told Seleucus I Nicator of "there being trees on which wool grows" in "Indica"; this may be a reference to "tree cotton", Gossypium arboreum, a native of the Indian subcontinent. According to the Columbia Encyclopedia: Cotton has been spun and dyed since prehistoric times.
It clothed the people of ancient India and China. Hundreds of years before the Christian era, cotton textiles were woven in India with matchless skill, their use spread to the Mediterranean countries. In Iran, the history of cotton dates back to the Achaemenid era; the planting of cotton was common in Merv and Pars of Iran. In Persian poets' poems Ferdowsi's Shahname, there are references to cotton. Marco Polo refers to the major products including cotton. John Chardin, a French traveler of the 17th century who visited Safavid Persia, spoke approvingly of the vast cotton farms of Persia. During the Han dynasty, cotton was grown by Chinese peoples in the southern Chinese province of Yunnan. Egyptians spun cotton in the first seven centuries of the Christian era. Handheld roller cotton gins had been used in India since the 6th century, was introduced to other countries from there. Between the 12th and 14th centuries, dual-roller gins appeared in China; the Indian version of the dual-roller gin was preval
In a reactive dye, a chromophore contains a substituent that reacts with the substrate. Reactive dyes have good fastness properties owing to the bonding. Reactive dyes are most used in dyeing of cellulose like cotton or flax, but wool is dyeable with reactive dyes. Reactive dyeing is the most important method for the coloration of cellulosic fibres. Reactive dyes can be applied on wool and nylon. Reactive dyes have a low utilization degree compared to other types of dyestuff, since the functional group bonds to water, creating hydrolysis. Reactive dyes had been tested in the late 1800s involving both adding functionalized dyes to the substrate and activating the substrate first followed by fixation of the dye; the first commercial success was described in the early 1950s. Rattee and Stephens at Imperial Chemical Industries popularlized the chlorotriazines as linkers between the substrate and the chromophore. Trichlorotriazines remain a popular platform for reactive dyes; the chromophore, with an amine functional group, is attached to the triazine, displacing one chloride: 3 + dye-NH2 → N3C3Cl2 + HClThe resulting dichlorotriazine can be affixed to the cellulose fibre by displacement of one of the two chloride groups: N3C3Cl2 + HO-cellulose → N3C3Cl + HClThe fixation process is conducted in a buffered alkaline dye bath.
An alternative fixation process, more dominant commercially is the vinylsulfonyl group. Like the chlorotriazines, this functional group adds to the hydroxyl groups of cellulose; the most popular version of this technology is Remazol. The dye is first attached to the ethylsulfonyl group. Reactive dyes are categorized by functional group. Dyestuffs with only one functional group sometimes have a low degree of fixation. To overcome this deficiency, dyestuffs containing two different reactive groups were developed; these dyestuffs containing two groups are known as bifunctional dyestuffs although some still refer to the original combination. Some contain two monochlorotriazines, others have a combination of the triazines and one vinyl sulfone group). Bifunctional dyes can be more tolerant to temperature deviations. Other bifunctionals have been created, only fixation degree in mind. Carbene dyes For more info Fundamental Chemistry of reactive dyes Advancements in Reactive Textile Dyes