1.
Fuel
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A fuel is any material that can be made to react with other substances so that it releases chemical or nuclear energy as heat or to be used for work. The concept was applied solely to those materials capable of releasing chemical energy but has since also been applied to other sources of heat energy such as nuclear energy. The heat energy released by reactions of fuels is converted into mechanical energy via a heat engine, other times the heat itself is valued for warmth, cooking, or industrial processes, as well as the illumination that comes with combustion. Fuels are also used in the cells of organisms in a known as cellular respiration. Hydrocarbons and related oxygen-containing molecules are by far the most common source of fuel used by humans, fuels are contrasted with other substances or devices storing potential energy, such as those that directly release electrical energy or mechanical energy. The first known use of fuel was the combustion of wood or sticks by Homo erectus near 2,000,000 years ago, throughout most of human history fuels derived from plants or animal fat were only used by humans. Charcoal, a derivative, has been used since at least 6,000 BCE for melting metals. It was only supplanted by coke, derived from coal, as European forests started to become depleted around the 18th century, charcoal briquettes are now commonly used as a fuel for barbecue cooking. Coal was first used as a fuel around 1000 BCE in China, coal was later used to drive ships and locomotives. By the 19th century, gas extracted from coal was being used for lighting in London. In the 20th and 21st centuries, the use of coal is to generate electricity. Fossil fuels were rapidly adopted during the revolution, because they were more concentrated and flexible than traditional energy sources. They have become a part of our contemporary society, with most countries in the world burning fossil fuels in order to produce power. Currently the trend has been towards renewable fuels, such as biofuels like alcohols, chemical fuels are substances that release energy by reacting with substances around them, most notably by the process of combustion. Most of the energy released in combustion was not stored in the chemical bonds of the fuel. Chemical fuels are divided in two ways, first, by their physical properties, as a solid, liquid or gas. Secondly, on the basis of their occurrence, primary and secondary, solid fuels include wood, charcoal, peat, coal, Hexamine fuel tablets, and pellets made from wood, corn, wheat, rye and other grains. Solid-fuel rocket technology also uses solid fuel, solid fuels have been used by humanity for many years to create fire
2.
Pyrotechnics
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Pyrotechnics is the science of using materials capable of undergoing self-contained and self-sustained exothermic chemical reactions for the production of heat, light, gas, smoke and/or sound. Its etymology stems from the Greek words pyro and tekhnikos, individuals responsible for the safe storage, handling, and functioning of pyrotechnic devices are referred to as pyrotechnicians. Proximate refers to the devices location relative to an audience. In the majority of jurisdictions, special training and licensing must be obtained from local authorities to legally prepare, many musical groups use pyrotechnics to enhance their live shows. Pink Floyd were without a doubt the innovators of pyrotechnic use in concerts, for instance, at the climax of their song Careful with That Axe, Eugene, a blast of smoke was set off at the back of the stage. Bands such as The Who, KISS and Queen, soon followed use of pyrotechnics in their shows, michael Jackson attempted using pyrotechnics in a 1984 Pepsi advertisement, where a stray spark caused a small fire in his hair. German industrial metal band Rammstein are renowned for their variety of pyrotechnics. Nightwish, Lordi and Green Day are also known for their vivid pyrotechnics in concert, many professional wrestlers have also used pyrotechnics as part of their entrances to the ring. Modern pyrotechnics are, in general, divided into categories based upon the type of effect produced or manufacturing method, the most common categories are, Airburst - Hanging charges designed to burst into spheres of sparks. Binary powders - Kits divided into separate oxidizer and fuel, intended to be mixed on site, comet - Brightly colored burning pellets resembling shooting stars. Mine - Tubes containing a lift charge intended to project stars, sparks, preloaded Smoke Pot - Cartridges designed to release a mushroom cloud of smoke. Concussion - Device designed to create a loud report, falls - Propellant with titanium burning in an open ended tube creating a falling spark effect. Fireballs / Mortar Hits - Short barreled device projecting smoky rolling ball of flame, flame Projector - Tube containing nitrocellulose granules that burn in pillars of colored flame. Flare - Short, high intensity flames or various colours, flash Cotton - Nitrated cotton string. Flashpaper - Sheets of nitrated paper resembling tissue paper, flash Pot - Short metal pot used with binary powders creating flash, smoke or sparks. Flash Tray - A long tube slit down one side to project a sheet of flash, gerb - A fountain of sparks. Lance - A Small colored flare tube used in making points of light lancework or pictures in fire, line Rockets - Whistling or colored rocket devices that travel along guide cables. Multi-Tube Article - Multiple effects chained together, pre-Mixed Powder - Powders intended to create various effects
3.
Fireworks
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Fireworks are a class of low explosive pyrotechnic devices used for aesthetic and entertainment purposes. The most common use of a firework is as part of a fireworks display, Fireworks competitions are also regularly held at a number of places. Fireworks take many forms to produce the four primary effects, noise, light, smoke and they may be designed to burn with colored flames and sparks including red, orange, yellow, green, blue, purple, and silver. Displays are common throughout the world and are the point of many cultural. Fireworks were invented in ancient China in the 7th century to scare evil spirits. Such important events and festivities as Chinese New Year and the Mid-Autumn Moon Festival were, China is the largest manufacturer and exporter of fireworks in the world. Fireworks are generally classified as to where they perform, either as a ground or aerial firework, in the latter case they may provide their own propulsion or be shot into the air by a mortar. The most common feature of fireworks is a paper or pasteboard tube or casing filled with the combustible material, a number of these tubes or cases are often combined so as to make, when kindled, a great variety of sparkling shapes, often variously colored. The skyrocket is a form of firework, although the first skyrockets were used in war. The aerial shell, however, is the backbone of todays commercial aerial display, such rocket technology has also been used for the delivery of mail by rocket and is used as propulsion for most model rockets. The earliest documentation of fireworks dates back to 7th century China, the fireworks were used to accompany many festivities. It is thus a part of the culture of China and had its origin there, the art and science of firework making has developed into an independent profession. In China, pyrotechnicians were respected for their knowledge of techniques in mounting firework displays. Chinese people originally believed that the fireworks could expel evil spirits and bring about luck, during the Song Dynasty, many of the common people could purchase various kinds of fireworks from market vendors, and grand displays of fireworks were also known to be held. In 1110, a fireworks display in a martial demonstration was held to entertain Emperor Huizong of Song. A record from 1264 states that a rocket-propelled firework went off near the Empress Dowager Gong Sheng, rocket propulsion was common in warfare, as evidenced by the Huolongjing compiled by Liu Bowen and Jiao Yu. In 1240 the Arabs acquired knowledge of gunpowder and its uses from China, with the development of chinoiserie in Europe, Chinese fireworks began to gain popularity around the mid-17th century. Lev Izmailov, ambassador of Peter the Great, once reported from China and his writings would be translated in 1765, resulting in the popularization of fireworks and further attempts to uncover the secrets of Chinese fireworks
4.
Cap gun
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A cap gun, cap pistol, or cap rifle is a toy gun that creates a loud sound simulating a gunshot and a puff of smoke when a small percussion cap is exploded. Cap guns were made of cast iron, but after World War II were made of zinc alloy. Some are arranged in rings of eight or twelve. There are also single caps, roll caps, and disk caps, cap guns first appeared following the end of the American Civil War in the mid-1860s, when firearms companies experimented with toy guns in order to stay in business. Cap guns became popular when the heroes of cinema and television rode through the West ridding the territories of villains. Many cap guns were named after or endorsed by leading matinee idols like Roy Rogers, Gene Autry, Hopalong Cassidy, The Lone Ranger, Tonto, Dale Evans, Marshal Matt Dillon, children all over the world emulated their heroes and collected and played with these toy guns. There were many types of cap guns, including guns from small Derringers, to larger rifles, one of the last famous ones to sell widely was a toy rifle named after the television show, The Rifleman, which aired from 1958 through early 1963. Other shows lasted longer, such as Gunsmoke, but those did not have as much kid-appeal as the shows. The pistols generally were in 3 styles, the semi-automatic, the revolver and the mock-revolver that looked like a regular revolver, the circular cap was placed into the 2-piece bullet and then when the gun was loaded and fired, it seemed more realistic. When the gun was fired, the spring pressure shot the plastic out of the end of the barrel. Eventually Mattel also came out with a model called Shootin Shells. Mattel produced an automatic firing cap weapon styled after the Thompson submachine gun, pulling back on a slide, which simulated the charging handle of the real Thompson, prepared the gun for firing by tensioning a spring. When the trigger was pulled the power would drive the mechanism. It was made initially for a Dick Tracy line of toys, then camouflaged for a Green Beret Guerilla Fighter line of weapons, ring cap guns are usually modeled after revolver pistols, with the cap ring placed in the cylinder section of the toy gun. Strip or paper cap guns use the cap strip in lieu of the cap ring. As in the style of gun, each pull of the trigger advances the cap strip forward, pulls back the hammer to the point where it releases. Potato or spud guns occasionally use a cap to provide a burst of gas to fire the projectile, one design employs a small reusable metal cartridge which has a recess for a cap at one end and a small drilling through to the other end, which holds the potato. Due to the low energy contained in a cap and the poor seal around the cartridge
5.
Flash (photography)
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A flash is a device used in photography producing a flash of artificial light at a color temperature of about 5500 K to help illuminate a scene. A major purpose of a flash is to illuminate a dark scene, other uses are capturing quickly moving objects or changing the quality of light. Flash refers either to the flash of light itself or to the flash unit discharging the light. Most current flash units are electronic, having evolved from single-use flashbulbs, modern cameras often activate flash units automatically. Flash units are built directly into a camera. Some cameras allow separate flash units to be mounted via an accessory mount bracket. In professional studio equipment, flashes may be large, standalone units, or studio strobes, studies of magnesium by Bunsen and Roscoe in 1859 showed that burning this metal produced a light with similar qualities to daylight. The potential application to photography inspired Edward Sonstadt to investigate methods of manufacturing magnesium so that it would burn reliably for this use and he applied for patents in 1862 and by 1864 had started the Manchester Magnesium Company with Edward Mellor. It also had the benefit of being a simpler and cheaper process than making round wire, mather was also credited with the invention of a holder for the ribbon, which formed a lamp to burn it in. The packaging also implies that the ribbon was not necessarily broken off before being ignited. An alternative to ribbon was flash powder, a mixture of powder and potassium chlorate, introduced by its German inventors Adolf Miethe. A measured amount was put into a pan or trough and ignited by hand, producing a brilliant flash of light, along with the smoke. This could be an activity, especially if the flash powder was damp. An electrically triggered flash lamp was invented by Joshua Lionel Cowen in 1899 and his patent describes a device for igniting photographers’ flash powder by using dry cell batteries to heat a wire fuse. Variations and alternatives were touted from time to time and a few found a measure of success in the marketplace, especially for amateur use. The use of powder in an open lamp was replaced by flashbulbs, magnesium filaments were contained in bulbs filled with oxygen gas. Manufactured flashbulbs were first produced commercially in Germany in 1929, such a bulb could only be used once, and was too hot to handle immediately after use, but the confinement of what would otherwise have amounted to a small explosion was an important advance. A later innovation was the coating of flashbulbs with a film to maintain bulb integrity in the event of the glass shattering during the flash
6.
Photography
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Typically, a lens is used to focus the light reflected or emitted from objects into a real image on the light-sensitive surface inside a camera during a timed exposure. With an electronic sensor, this produces an electrical charge at each pixel. A negative image on film is used to photographically create a positive image on a paper base, known as a print. The word photography was created from the Greek roots φωτός, genitive of φῶς, light and γραφή representation by means of lines or drawing, several people may have coined the same new term from these roots independently. Johann von Maedler, a Berlin astronomer, is credited in a 1932 German history of photography as having used it in an article published on 25 February 1839 in the German newspaper Vossische Zeitung. Both of these claims are now widely reported but apparently neither has ever been confirmed as beyond reasonable doubt. Credit has traditionally given to Sir John Herschel both for coining the word and for introducing it to the public. Photography is the result of combining several technical discoveries, later Greek mathematicians Aristotle and Euclid also independently described a pinhole camera in the 5th and 4th centuries BCE. Daniele Barbaro described a diaphragm in 1566, wilhelm Homberg described how light darkened some chemicals in 1694. The fiction book Giphantie, published in 1760, by French author Tiphaigne de la Roche, the discovery of the camera obscura that provides an image of a scene dates back to ancient China. Leonardo da Vinci mentions natural camera obscura that are formed by dark caves on the edge of a sunlit valley, a hole in the cave wall will act as a pinhole camera and project a laterally reversed, upside down image on a piece of paper. So the birth of photography was primarily concerned with inventing means to capture, renaissance painters used the camera obscura which, in fact, gives the optical rendering in color that dominates Western Art. The camera obscura literally means dark chamber in Latin and it is a box with a hole in it which allows light to go through and create an image onto the piece of paper. Around the year 1800, British inventor Thomas Wedgwood made the first known attempt to capture the image in a camera obscura by means of a light-sensitive substance and he used paper or white leather treated with silver nitrate. The shadow images eventually darkened all over, the first permanent photoetching was an image produced in 1822 by the French inventor Nicéphore Niépce, but it was destroyed in a later attempt to make prints from it. Niépce was successful again in 1825, in 1826 or 1827, he made the View from the Window at Le Gras, the earliest surviving photograph from nature. Because Niépces camera photographs required a long exposure, he sought to greatly improve his bitumen process or replace it with one that was more practical. With an eye to eventual commercial exploitation, the partners opted for total secrecy, Daguerres efforts culminated in what would later be named the daguerreotype process
7.
Flare (countermeasure)
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A flare or decoy flare is an aerial infrared countermeasure used by a plane or helicopter to counter an infrared homing surface-to-air missile or air-to-air missile. Flares are commonly composed of a composition based on magnesium or another hot-burning metal. The aim is to make the infrared-guided missile seek out the signature from the flare rather than the aircrafts engines. In contrast to radar-guided missiles, IR-guided missiles are very difficult to find as they approach aircraft and they do not emit detectable radar, and they are generally fired from a rear visual-aspect, directly toward the engines. In most cases, pilots have to rely on their wingmen to spot the missiles smoke trail, more advanced electro-optical systems can detect missile launches automatically from the distinct thermal emissions of a missiles rocket motor. The aircraft would then pull away at an angle from the flare. Optimally, the seeker head is then confused by this change in temperature and flurry of new signatures. The most modern IR-guided missiles have sophisticated on-board electronics that help discriminate between flares and targets, reducing the effectiveness of countermeasures, consequently, flare dispensers are now fitted to helicopters. Indeed almost all of the UKs helicopters, whether they are transport or attack models, are equipped with flare dispenser or missile approach warning systems, similarly, the US armed forces have adopted defensive technology on their helicopters. This caused concerns in some European countries, which proceeded to ban such aircraft from landing at their airports, a flare goes through three main stages, ignition, deployment, and decoying. Most flares, like the MJU-27A/B flares, must be kept in a storage compartment before deployment. These flares, known as flares, are made of special materials that ignite when they come in contact with the air. This is a safety and convenience factor, since attempting to ignite a flare inside the fuselage, flares are most commonly gravity-fed from a dispenser inside the aircrafts fuselage. These dispensers can be programmed by the pilot or ground crew to dispense flares in short intervals, one at a time, long intervals, or in clusters. Most currently used flares are of the variety, and thus the dispensers do not have to ignite. With pyrotechnic flares, a lanyard automatically pulls off a friction cap covering the end of the flare as it falls from the dispenser. A friction surface inside the cap rubs against the end of the flare. Flares burn at thousands of degrees, which is hotter than the exhaust of a jet engine
8.
Magic (illusion)
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Magic is one of the oldest performing arts in the world in which audiences are entertained by staged tricks or illusions of seemingly impossible or supernatural feats using natural means. These feats are called magic tricks, effects, or illusions, the term magic etymologically derives from the Greek word mageia. In ancient times, Greeks and Persians had been at war for centuries, ritual acts of Persian priests came to be known as mageia, and then magika—which eventually came to mean any foreign, unorthodox, or illegitimate ritual practice. The first book containing explanations of magic tricks appeared in 1584, during the 17th century, many similar books were published that described magic tricks. Until the 18th century, magic shows were a source of entertainment at fairs. A founding figure of modern entertainment magic was Jean Eugène Robert-Houdin, John Henry Anderson was pioneering the same transition in London in the 1840s. Towards the end of the 19th century, large magic shows permanently staged at big theatre venues became the norm, as a form of entertainment, magic easily moved from theatrical venues to television magic specials. Performances that modern observers would recognize as conjuring have been practiced throughout history, for many recorded centuries, magicians were associated with the devil and the occult. During the 19th and 20th centuries, many stage magicians even capitalized on this notion in their advertisements. The same level of ingenuity that was used to produce famous ancient deceptions such as the Trojan Horse would also have used for entertainment. They were also used by the practitioners of various religions and cults from ancient times onwards to frighten uneducated people into obedience or turn them into adherents, however, the profession of the illusionist gained strength only in the 18th century, and has enjoyed several popular vogues since. Opinions vary among magicians on how to categorize a given effect, Magicians may pull a rabbit from an empty hat, make something seem to disappear, or transform a red silk handkerchief into a green silk handkerchief. Magicians may also destroy something, like cutting a head off, other illusions include making something appear to defy gravity, making a solid object appear to pass through another object, or appearing to predict the choice of a spectator. Many magical routines use combinations of effects, one of the earliest books on the subject is Gantzionys work of 1489, Natural and Unnatural Magic, which describes and explains old-time tricks. Among the tricks discussed were sleight-of-hand manipulations with rope, paper, at the time, fear and belief in witchcraft was widespread and the book tried to demonstrate that these fears were misplaced. All obtainable copies were burned on the accession of James I in 1603 and it began to reappear in print in 1651. In the early 18th century, as belief in witchcraft was waning, a notable figure in this transition was the English showman, Isaac Fawkes, who began to promote his act in advertisements from the 1720s – he even claimed to have performed for King George II. He throws up a Pack of Cards, and causes them to be living birds flying about the room and he causes living Beasts, Birds, and other Creatures to appear upon the Table
9.
Movie theater
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A movie theater or movie theatre is a venue, usually a building, that contains an auditorium for viewing films, for entertainment. Most, but not all, movie theaters are commercial operations catering to the general public, Some movie theaters, however, are operated by non-profit organizations or societies which charge members a membership fee to view films. The film is projected with a projector onto a large projection screen at the front of the auditorium while the dialogue, sounds. Since the 1970s, subwoofers have used for low-pitched sounds. In the 2010s, most movie theaters are equipped for digital cinema projection, removing the need to create, a great variety of films are shown at cinemas, ranging from animated films for children, blockbusters for general audiences and documentaries for patrons who are interested in non-fiction topics. The smallest movie theaters have a viewing room with a single screen. In the 2010s, most movie theaters have multiple screens, the largest theater complexes, which are called multiplexes—a design developed in the U. S. in the 1960s—have up to 25 screens. The audience members sit on padded seats which in most theaters are set up on a sloped floor. Movie theaters typically sell soft drinks, popcorn and candy and some theaters also sell hot fast food, in some jurisdictions, movie theaters are licensed to sell alcoholic drinks. A movie theater may also be referred to as a theatre, movie house, film house. In the US, theater has long been the preferred spelling, while in the UK, Canada, the latter terms, as well as their derivative adjectives cinematic and kinematic, ultimately derive from Greek κινῆμα, κινήματος —movement, motion. In the countries where those terms are used, the theatre is usually reserved for live performance venues. Colloquial expressions, mostly applied to motion pictures and motion picture theaters collectively, include the silver screen, specific to North American term is the movies, while specific terms in the UK are the pictures, the flicks and for the facility itself the flea pit. A screening room is a theater, often a private one. Open air place in ancient times for viewing spectacles and plays, the term theater comes from the Old French word theatre, from the 12th century and. The use of the theatre to mean a building where plays are shown dates from the 1570s in the English language. The earliest precursors to movies were magic lantern shows, magic lanterns used a glass lens, a shutter and a powerful lamp to project images from glass slides onto a white wall or screen. The invention of the Argand lamp in the 1790s, limelight in the 1820s, the magic lantern could project rudimentary moving images, which was achieved by the use of various types of mechanical slides
10.
Theatre
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The performers may communicate this experience to the audience through combinations of gesture, speech, song, music, and dance. Elements of art, such as painted scenery and stagecraft such as lighting are used to enhance the physicality, presence, the specific place of the performance is also named by the word theatre as derived from the Ancient Greek θέατρον, itself from θεάομαι. Modern theatre, broadly defined, includes performances of plays and musical theatre, there are connections between theatre and the art forms of ballet, opera and various other forms. The city-state of Athens is where western theatre originated, participation in the city-states many festivals—and mandatory attendance at the City Dionysia as an audience member in particular—was an important part of citizenship. The Greeks also developed the concepts of dramatic criticism and theatre architecture, Actors were either amateur or at best semi-professional. The theatre of ancient Greece consisted of three types of drama, tragedy, comedy, and the satyr play, the origins of theatre in ancient Greece, according to Aristotle, the first theoretician of theatre, are to be found in the festivals that honoured Dionysus. The performances were given in semi-circular auditoria cut into hillsides, capable of seating 10, the stage consisted of a dancing floor, dressing room and scene-building area. Since the words were the most important part, good acoustics, the actors wore masks appropriate to the characters they represented, and each might play several parts. Athenian tragedy—the oldest surviving form of tragedy—is a type of dance-drama that formed an important part of the culture of the city-state. Having emerged sometime during the 6th century BCE, it flowered during the 5th century BCE, no tragedies from the 6th century BCE and only 32 of the more than a thousand that were performed in during the 5th century BCE have survived. We have complete texts extant by Aeschylus, Sophocles, and Euripides, the origins of tragedy remain obscure, though by the 5th century BCE it was institution alised in competitions held as part of festivities celebrating Dionysus. As contestants in the City Dionysias competition playwrights were required to present a tetralogy of plays, the performance of tragedies at the City Dionysia may have begun as early as 534 BCE, official records begin from 501 BCE, when the satyr play was introduced. More than 130 years later, the philosopher Aristotle analysed 5th-century Athenian tragedy in the oldest surviving work of dramatic theory—his Poetics, Athenian comedy is conventionally divided into three periods, Old Comedy, Middle Comedy, and New Comedy. Old Comedy survives today largely in the form of the surviving plays of Aristophanes. New Comedy is known primarily from the papyrus fragments of Menander. Aristotle defined comedy as a representation of people that involves some kind of blunder or ugliness that does not cause pain or disaster. In addition to the categories of comedy and tragedy at the City Dionysia, finding its origins in rural, agricultural rituals dedicated to Dionysus, the satyr play eventually found its way to Athens in its most well-known form. Satyrs themselves were tied to the god Dionysus as his loyal companions, often engaging in drunken revelry
11.
Polytetrafluoroethylene
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Polytetrafluoroethylene is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. The best known name of PTFE-based formulas is Teflon by Chemours. Chemours is a spin-off of DuPont Co. which discovered the compound in 1938, PTFE is a fluorocarbon solid, as it is a high-molecular-weight compound consisting wholly of carbon and fluorine. PTFE is hydrophobic, neither water nor water-containing substances wet PTFE, PTFE has one of the lowest coefficients of friction of any solid. PTFE is used as a coating for pans and other cookware. It is very non-reactive, partly because of the strength of carbon–fluorine bonds, where used as a lubricant, PTFE reduces friction, wear and energy consumption of machinery. It is commonly used as a material in surgical interventions. Also, it is employed as coating on catheters, this interferes with the ability of bacteria and other infectious agents to adhere to catheters. PTFE was accidentally discovered in 1938 by Roy Plunkett while he was working in New Jersey for DuPont. Since Plunkett was measuring the amount of gas used by weighing the bottle, he became curious as to the source of the weight and he found the bottles interior coated with a waxy white material that was oddly slippery. Analysis showed that it was polymerized perfluoroethylene, with the iron from the inside of the container having acted as a catalyst at high pressure, Kinetic Chemicals patented the new fluorinated plastic in 1941, and registered the Teflon trademark in 1945. By 1948, DuPont, which founded Kinetic Chemicals in partnership with General Motors, was producing two million pounds of Teflon brand PTFE per year in Parkersburg, West Virginia. In 1954, the wife of French engineer Marc Grégoire urged him to try the material he had been using on fishing tackle on her cooking pans and he subsequently created the first Teflon-coated, non-stick pans under the brandname Tefal. In the United States, Marion A. Trozzolo, who had been using the substance on scientific utensils, marketed the first US-made Teflon-coated pan, The Happy Pan, however, Tefal was not the only company to utilize PTFE in nonstick cookware coatings. Other cookware companies, such as Meyer Corporations Anolon, use Teflon nonstick coatings purchased from DuPont, in the 1990s, it was found that PTFE could be radiation cross-linked above its melting point in an oxygen-free environment. Electron beam processing is one example of radiation processing, cross-linked PTFE has improved high-temperature mechanical properties and radiation stability. This was significant because, for years, irradiation at ambient conditions has been used to break down PTFE for recycling. This radiation-induced chain scission allows it to be more easily reground, PTFE is produced by free-radical polymerization of tetrafluoroethylene
12.
Static electricity
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Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it is able to move away by means of a current or electrical discharge. Static electricity is named in contrast with current electricity, which flows through wires or other conductors, a static electric charge can be created whenever two surfaces contact and separate, and at least one of the surfaces has a high resistance to electric current. The familiar phenomenon of a static shock–more specifically, an electrostatic discharge–is caused by the neutralization of charge, materials are made of atoms that are normally electrically neutral because they contain equal numbers of positive charges and negative charges. The phenomenon of static electricity requires a separation of positive and negative charges, when two materials are in contact, electrons may move from one material to the other, which leaves an excess of positive charge on one material, and an equal negative charge on the other. When the materials are separated they retain this charge imbalance and this is known as the triboelectric effect and results in one material becoming positively charged and the other negatively charged. The polarity and strength of the charge on a material once they are separated depends on their positions in the triboelectric series. The triboelectric effect is the cause of static electricity as observed in everyday life. Contact-induced charge separation causes your hair to stand up and causes static cling, pressure-induced charge separation Applied mechanical stress generates a separation of charge in certain types of crystals and ceramics molecules. Heat-induced charge separation Heating generates a separation of charge in the atoms or molecules of certain materials, all pyroelectric materials are also piezoelectric. The atomic or molecular properties of heat and pressure response are closely related, charge-induced charge separation A charged object brought close to an electrically neutral object causes a separation of charge within the neutral object. Charges of the same polarity are repelled and charges of the opposite polarity are attracted, as the force due to the interaction of electric charges falls off rapidly with increasing distance, the effect of the closer charges is greater and the two objects feel a force of attraction. The effect is most pronounced when the object is an electrical conductor as the charges are more free to move around. Careful grounding of part of an object with a charge separation can permanently add or remove electrons, leaving the object with a global. This process is integral to the workings of the Van de Graaff generator, removing or preventing a buildup of static charge can be as simple as opening a window or using a humidifier to increase the moisture content of the air, making the atmosphere more conductive. Air ionizers can perform the same task, fabric softeners and dryer sheets used in washing machines and clothes dryers are an example of an antistatic agent used to prevent and remove static cling. Many semiconductor devices used in electronics are particularly sensitive to static discharge, conductive antistatic bags are commonly used to protect such components. People who work on circuits that contain these devices often ground themselves with an antistatic strap
