Plastics are materials composed of various synthetic or semi-synthetic organic compounds that are easily formed and can be formed into solids.
Plasticity is the common property of all materials that can be irreversibly transformed without breaking but, in moldable polymer classes, this happens in such a way that their original name comes from this particular ability.
Plastics are usually organic polymers with high molecular mass and often contain other substances. They are usually synthetic, most often derived from petrochemicals; however, various variants are made from renewable materials such as polylactic acid from corn or cellulose from cotton linters.
Because of its low cost, ease of manufacture, versatility, and water resistance, plastics are used in many products of different scales, including paper clips and spacecraft. They have won over traditional materials, such as wood, stone, horns and bones, leather, metal, glass, and ceramics, in some products that were previously allowed to become natural materials.
In developed countries, about one-third of plastics are used in packaging and roughly the same in in-building buildings such as piping, piping or vinyl wall coverings. Other uses include cars (up to 20% plastic), furniture, and toys. In developing countries, plastic applications may be different - 42% of Indian consumption is used in packaging.
Plastics have many uses in the medical field as well, with the introduction of polymer implants and other medical devices that are derived at least partly from plastic. Plastic surgery field is not given a name for the use of plastic materials, but rather the meaning of word plasticity, in connection with the rearrangement of meat.
The first synthetic plastic in the world is bakelite, which was discovered in New York in 1907 by Leo Baekeland who coined the term 'plastics'. Many chemists have contributed to the science of plastic materials, including Nobel laureate Hermann Staudinger who has been called "the father of polymer chemistry" and Herman Mark, known as the "father of polymer physics".
The success and dominance of plastics beginning in the early 20th century led to environmental concerns about slow decomposition rates after being disposed of as waste due to large molecular compositions. Towards the end of the century, one approach to this problem is filled with widespread efforts towards recycling.
Video Plastic
Etymology
The word plastic comes from the Greek word ????????? ( plastikos ) which means "capable of being formed or formed" and, in turn, from ??????? ( plastos ) which means "printed".
The plasticity, or flexibility, of the material during manufacture allows it to be thrown, pressed, or extruded into various forms, such as films, fibers, plates, tubes, bottles, boxes, among many others.
Common noun plastics should not be confused with technical adjectives plastics . The adjectives apply to any material that undergoes plastic deformation, or permanent form changes, when strained beyond a certain point. For example, stamped or forged aluminum shows plasticity in this sense, but not plastics in common sense. Instead, some plastics will, in their finished form, break before deformation and hence not plastics in a technical sense.
Maps Plastic
Structure
Most plastics contain organic polymers. Most of these polymers are formed from carbon chain chain , 'pure' or with the addition of: oxygen, nitrogen, or sulfur. The chain consists of many repeating units, formed from monomers. Each polymer chain will have several thousand repeating units.
The spine is part of a chain that is on the "main line", linking together a large number of repeating units.
To adjust the properties of plastics, different groups of molecules "hang" from this backbone. This pendant unit is usually "hung" on a monomer, before the monomer itself is connected together to form a polymer chain. This is the structure of this side chain that affects the nature of the polymer.
The molecular structure of the repetition unit can be well tuned to affect specific properties in the polymer.
Property and classification
Plastics are usually classified by: the chemical structure of the backbone and the polymer side chain; several important groups in this classification are: acrylic, polyester, silicon, polyurethane, and halogenated plastics.
Plastics can also be classified by: chemical processes used in their synthesis, such as: condensation, polyadition, and cross linkages.
Plastics can also be classified by: their various physical properties, such as: hardness, density, tensile strength, heat resistance and glass transition temperature, and by their chemical properties, such as polymer organic chemistry and its resistance and reaction to it. various chemical products and processes, such as: organic solvents, oxidation, and ionizing radiation. In particular, most plastics will melt after heating up to several hundred degrees centigrade.
Other classifications are based on qualities relevant to the manufacture or design of the product. Examples of such quality and grade are: thermoplastics and thermosets, conductive polymers, biodegradable plastics and other engineering plastics and plastics with special structures, such as elastomers.
Thermoplastics and polymer thermosetting
One important classification of plastics is with the immortality or impermanence of their shape, or whether they are: thermoplastics or thermosetting polymers. Thermoplastics are plastics which, when heated, have no chemical change in their composition and can be formed again and again. Examples include: polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyvinyl chloride (PVC). General thermoplastics range from 20,000 to 500,000 amu, while thermosets are assumed to have infinite molecular weights.
Thermoset , or thermosetting polymers , can melt and form only once: once they are solidified, they remain solid. In the thermosetting process, chemical reactions occur which can not be changed. Rubber vulcanization is an example of a thermosetting process: before heating with sulfur, polyisoprene is a tacky and slightly watery substance; after vulcanization, this product is rigid and not sticky.
Amorphous plastic and crystal plastic
Many plastics are completely amorphous, such as: all thermosets; polystyrene and copolymers thereof; and polymethyl methacrylate.
However, some partially crystalline and partially amorphous plastics are in molecular structures, giving them a good melting point, the temperature at which an attractive intermolecular strength is overcome, and also one or more glass transitions, the temperature above the extent to which local molecular flexibility is substantially increased. These so-called semi-crystalline plastics include: polyethylene, polypropylene, polyvinyl chloride, polyamides (nylon), polyesters and some polyurethanes.
Conductive polymers
Intrinsically Conducting Polymers (ICP) are organic polymers that conduct electricity. While plastics can be electrically conductive, with a conductivity of up to 80 kS/cm in stretch-oriented polyacetylene, they are still unsuitable for most metals such as copper having a conductivity of several hundred kS/cm. However, this is a growing field.
Biodegradable and bioplastic plastics
Biodegradable plastics are plastics that degrade, or break down, on exposure: sunlight or ultraviolet radiation, water or moisture, bacteria, enzymes or wind abrasion. In some cases, rodent attacks, pests, or insects can also be considered as a form of biodegradation or environmental degradation.
Some degradation modes require the plastic to be exposed on the surface (aerobic), while other modes will only be effective if certain conditions exist in the waste or composting system (anaerobic).
Some companies produce biodegradable additives, to improve biodegradation. Plastics can have a starch powder added as a filler to be more easily degraded, but this still does not lead to total plastic damage.
Some researchers have genetically engineered bacteria to synthesize completely biodegradable plastics, such as Biopol; However, this is expensive nowadays.
Bioplastics
While most plastics are produced from petrochemicals, bioplastics are made substantially from renewable plant ingredients such as: cellulose and starch. Because both for the limited limits of petrochemical reserves and the threat of global warming, the development of bioplastics is a growing field.
However, the development of bioplastics starts from a very low base and, to date, does not compare significantly with petrochemical production. Estimated global production capacity for biologically derived materials is 327,000 ton/year. In contrast, global production of polyethylene (PE) and polypropylene (PP), the world's leading petrochemical polyolefin, is estimated to reach more than 150 million tonnes by 2015.
Type
General plastics
The development of plastics has evolved from the use of natural plastic materials (eg, chewing gum, lacquer) to the use of chemically modified natural materials (eg natural rubber, nitrocellulose, collagen, galalite) and eventually into completely synthetic molecules (eg, bakelite, epoxy , polyvinyl chloride). Early plastics are bio-derived materials such as eggs and blood proteins, which are organic polymers. In about 1600 BC, Mesoamericans used natural rubber for balls, bands, and sculptures. Treated cattle horns were used as windows for lanterns in the Middle Ages. Materials that mimic the horn properties are developed by treating milk proteins (casein) with alkali.
In the nineteenth century, when the chemical industry developed during the Industrial Revolution, much of the material was reported. The development of plastics was also accelerated by Charles Goodyear's discovery of vulcanization to thermoset materials derived from natural rubber.
Parkesine (nitrocellulose) is considered to be the first man-made plastic. The plastic material was patented by Alexander Parkes, in Birmingham, England in 1856. It was inaugurated at the 1862 Great International Exhibition in London. Parkesine won a bronze medal at the 1862 World Expo in London. Parkesine is made from cellulose (the main component of plant cell walls) treated with nitric acid as a solvent. The output of the process (commonly known as cellulose nitrate or pyroxilin) ​​can be dissolved in alcohol and harden into a transparent and elastic material that can be formed when heated. By inserting the pigment into the product, it can be made to resemble ivory.
In 1897, Hanover, the owner of the German bulk print Wilhelm Krische was assigned to develop an alternative to the blackboard. The horn-shaped plastic produced from the milk protein casein was developed in collaboration with Austrian chemist (Friedrich) Adolph Spitteler (1846-1940). The end result is not suitable for the original purpose. In 1893, the French chemist Auguste Trillat found a way to dissolve the casein by immersing it in formaldehyde, producing a material marketed as galalith.
In the early 1900s, Bakelite, the first synthetic thermoset, was reported by Belgian chemist Leo Baekeland using phenol and formaldehyde.
After World War I, improvements in chemical technology caused an explosion in new plastic forms, with mass production beginning in the 1940s and 1950s (around World War II). Among the earliest examples in the new polymer wave are polystyrene (PS), first produced by BASF in the 1930s, and polyvinyl chloride (PVC), first manufactured in 1872 but commercially produced in the late 1920s. In 1923, Durite Plastics Inc. is the first phenol-furfural resin manufacturer. In 1933, polyethylene was discovered by Imperial Chemical Industries (ICI) researchers Reginald Gibson and Eric Fawcett.
In 1954, polypropylene was invented by Giulio Natta and began production in 1957.
In 1954, expanded polystyrene (used for building insulation, packaging, and cups) was discovered by Dow Chemical. The discovery of Polyethylene terephthalate (PET) was credited to employees of the Calico Printers Association in England in 1941; it was licensed to DuPont for the US and ICI if not, and as one of several suitable plastics as a substitute for glass in many circumstances, resulting in widespread use for bottles in Europe.
Plastic industry
Plastic manufacturing is a major part of the chemical industry, and some of the world's largest chemical companies have been involved since the early days, such as industry leaders BASF and Dow Chemical.
In 2014, sales of the top fifty companies totaled $ 961.3 billion. The companies come from about 18 countries as a whole, with more than half of companies on the US-based list. Many of the top 50 plastic companies are concentrated in just three countries:
- United States - 12
- Japanese - 8
- German - 6
BASF is the world's largest chemical producer for the ninth consecutive year.
Trade associations representing industries in the US include the American Chemistry Council.
Industry standard
Many plastic properties are determined by the standards specified by ISO, such as:
- ISO 306 - Thermoplastics
Many of the properties of plastics are determined by the UL Standard, the tests determined by Underwriters Laboratories (UL), such as:
- Flammability - UL94
- High voltage arc tracing rate - UL746A
- Comparative Tracking Index
Additive
Mixed into most plastics is an additional organic or inorganic compound. The average content of additives is a few percent. Much controversy related to plastics is actually related to additives: organotin compounds are highly toxic.
Typical additives include:
Stabilizer
Polymer stabilizers extend the life of the polymer by suppressing the degradation resulting from UV rays, oxidation, and other phenomena. Typical Stabilzers thus absorb UV light or function as an antioxidant.
Charger
Many plastics contain fillers, to improve performance or reduce production costs. Usually the filler is a mineral origin, for example, lime. Other fillers include: starch, cellulose, wood flour, ivory dust and zinc oxide.
- most fillers are relatively inert and inexpensive materials, making the product cheaper by weight.
- stabilizing additives including fire retardants, to lower the material's combustible level.
- some fillers are more chemically active and are called: reinforcing agents.
Plasticizers
Plasticizer, with mass, is often the most abundant additive. These oily but non-combustible compounds are mixed in plastics to improve the rheology, because many organic polymers are too rigid for certain applications.
Dyes
Dyes are another common additive, although the contribution of the weight is small.
Toxicity
Pure plastics have low toxicity due to their inability in water and because they are inert biochemically, due to their large molecular weight. Plastic products contain various additives, some of which can be toxic. For example, plasticizers such as adipate and phthalate are often added to the brittle plastic such as polyvinyl chloride to make it flexible enough to be used in food packaging, toys, and many other items. Traces of these compounds may be removed from the product. Due to concerns over the effects of leachate, the EU has limited the use of DEHP (di-2-ethylhexyl phthalate) and other phthalates in some applications, and the United States has limited the use of DEHP, DPB, BBP, DINP, DIDP, and Dnop in toys, children and child care articles under the Consumer Product Security Enhancement Act. Several washing compounds from food polystyrene containers have been proposed to disrupt hormone function and suspected human carcinogens. Other chemicals that have potential concerns include alkylphenols.
While the finished plastics may not be toxic, the monomers used in the manufacture of parent polymers may be toxic. In some cases, small amounts of these chemicals may remain trapped in the product unless appropriate processing is used. For example, the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) has recognized vinyl chloride, PVC precursor, as a human carcinogen.
Bisphenol A (BPA)
Some polymers may also break down into monomers or other toxic substances when heated. In 2011, it was reported that "almost all plastic products" samples released chemicals with estrogenic activity, although the researchers identified a plastic that did not leach chemicals with estrogenic activity.
The main building block of polycarbonate, bisphenol A (BPA), is an endocrine disrupter such as estrogen that can seep into food. Research in the Environmental Health Perspective found that BPA washed from canned coating, dental cover, and polycarbonate bottles can increase the weight of children's laboratory animals. Recent animal studies show that even low-grade exposure to BPA results in insulin resistance, which can lead to inflammation and heart disease.
In January 2010, the LA Times newspaper reported that the US FDA spent $ 30 million to investigate BPA indications linked to cancer.
Bis (2-ethylhexyl) adipate, present in PVC-based plastic wrap, is also a concern, as are volatile organic compounds present in the odor of new cars.
The EU has a permanent ban on the use of phthalates in toys. In 2009, the United States government banned certain types of phthalates commonly used in plastics.
Environmental effects
Most plastics are durable and greatly decreased, because their chemical structure makes them resistant to many natural processes of degradation. However, microbial species that are capable of degrading the plastic are known to science, and some are potentially useful for the disposal of certain class of plastic waste.
- In 1975 a team of Japanese scientists who examined a wastewater pool from a nylon plant found a strain of Flavobacterium that digested certain byproducts of nylon preparation 6, such as a linear dimer of 6-aminohexanoate. Nylon 4 or polybutyrolactam can be degraded by (ND-10 and ND-11) strands of Pseudomonas sp. found in mud. It produces? -aminobutyric acid (GABA) as a by-product.
- Some species of soil mushrooms can consume polyurethane. These include two species of the Ecuadorian Pestalotiopsis fungus that can consume aerobic polyurethane and also under anaerobic conditions such as those at the base of the landfill.
- The methanogenic consortium degrades styrene, using it as a carbon source. Pseudomonas putida can convert styrene oil into various biodegradable polyhydroxyalkanoates.
- Microbial communities isolated from soil samples mixed with starch have been shown to degrade polypropylene.
- Aspergillus fumigatus fungus effectively lowers plasticized PVC. Phanerochaete chrysosporium has grown on PVC in mineral salt agar. Phanerochaete chrysosporium, Lentinus tigrinus, Aspergillus niger, and Aspergillus sydowii can also effectively lower PVC. Phanerochaete chrysosporium is grown on PVC in mineral salt agar.
- Acinetobacter has been found to decrease most of the low molecular weight polyethylene oligomers. When used in combination, Pseudomonas fluorescens and Sphingomonas can lose more than 40% of the weight of plastic bags in less than three months. Thermophilic bacteria Brevibacillus borstelensis (strain 707) was isolated from soil samples and was found capable of using low density polyethylene as a single carbon source when incubated at 50 degrees Celsius. Pre-exposure to ultraviolet plastic radiation breaks chemical bonds and helps biodegradation; the longer the period of UV exposure, the greater the promotion of degradation.
- More unwanted, harmful molds are found in the space station, a fungus that degrades the rubber into an easily digestible form.
- Some species of yeast, bacteria, algae and moss are found to grow in synthetic polymer artifacts in museums and on archaeological sites.
- In the plastic-polluting waters of the Sargasso Sea, bacteria have been found that consume different types of plastics; but it is not known to what extent these bacteria effectively cleanse toxins rather than just releasing them into the marine microbial ecosystem.
- Plastic feeding microbes have also been found in landfills.
- Nocardia can decrease PET with esterase enzymes.
- Opium Geotrichum mushrooms, found in Belize, have been found to consume polycarbonate plastics found in CDs.
- Phenol-formaldehyde, commonly known as bakelite, is degraded by the white fungus Phanerochaete chrysosporium fungus.
- Futuro homes are made of fiberglass reinforced polyester, polyester-polyurethane, and poly (methylmethacrylate.) One such house was found to be destroyed by Cyanobacteria and Archaea.
There are different estimates of how much plastic waste was produced in the last century. With one estimate, one billion tons of plastic waste has been discarded since the 1950s. Others estimate cumulative human production of 8.3 billion tons of plastic, which is 6.3 billion tons of waste, with recycling rates of only 9%. Much of this material can last for centuries or longer, given the real persistence of natural ingredients that resemble structures such as amber.
The presence of plastic, especially micro, in the food chain is increasing. In 1960 micro was observed in the gut of seabirds, and has since been found in increased concentrations. Long-term effects of plastics in the food chain are poorly understood. In 2009, it was estimated that 10% of modern waste is plastic, although estimates vary by region. Meanwhile, 50-80% of debris in marine areas is plastic.
Prior to the Montreal Protocol, CFCs were generally used in the manufacture of polystyrene, and thus the production of polystyrene contributed to the depletion of the ozone layer.
Climate change
Plastic effects on global warming vary. Plastics are generally made of petroleum. If the plastic is burned, it increases carbon emissions; if placed in a landfill, it becomes a carbon sink even though biodegradable plastics have caused methane emissions. Because of the lighter plastic than glass or metal, plastic can reduce energy consumption. For example, packing drinks in PET plastic rather than glass or metal is estimated to save 52% in transport energy.
Plastic production
Plastic production from crude oil requires 62 to 108 MJ/kg (taking into account the average efficiency of 35% of US utility centers). Producing silicon and semiconductors for modern electronic equipment consumes even more energy: 230 to 235 MJ/Kg of silicon, and about 3,000 MJ/Kg of semiconductors. This is much higher than the energy required to produce many other materials, eg. iron (from iron ore) requires 20-25 MJ/kg of energy, glass (from sand, etc.) 18-35 MJ/kg, steel (from iron) 20-50 MJ/Kg, paper (from wood) 25-50 MJ/Kg.
Incineration of plastics
High temperature controlled incineration, above 850 ° C for two seconds, is performed by selective additional heating, breaking down the toxic dioxins and furans from plastic combustion, and is widely used in municipal solid waste incineration. Municipal solid waste incinerators also typically include exhaust gas treatment to reduce further pollutants. This is necessary because uncontrolled plastic incineration produces dibenzo-p-dioxins polychlorinate, a carcinogen (cancer-causing chemical). The problem occurs because the heat content of the waste stream varies. Open burning of plastic occurs at lower temperatures, and usually releases toxic fumes.
Pyrolitical Release
Plastics can be decomposed into hydrocarbon fuels, because plastics include hydrogen and carbon. One kilogram of plastic waste generates about one liter of hydrocarbons.
Recycling
Thermoplastics can be impregnated and reused, and thermoset plastics can be milled and used as fillers, although the purity of the material tends to decrease with each cycle of reuse. There are methods by which plastics can be broken down into raw material conditions.
The biggest challenge to recycle plastics is the difficulty of automating the sorting of plastic waste, making it labor-intensive. Typically, workers sort plastic by looking at the resin identification code, although common containers such as soda bottles can be sorted from memory. Typically, the PETE bottle cap is made of a different type of plastic that can not be recycled, which presents additional problems for the sorting process. Other materials that can be recycled such as metal are easier to process mechanically. However, a new process of mechanical sorting is being developed to increase the capacity and efficiency of plastic recycling.
While containers are usually made of one type and plastic color, making it relatively easy to sort, consumer products such as cell phones may have many small parts consisting of more than a dozen different types and plastic colors. In such cases, the resources required to separate the plastic far exceed its value and the item is discarded. However, developments are taking place in the active disassembly field, which may cause more product components to be reused or recycled. Recycling certain types of plastics can also be unprofitable. For example, polystyrene is rarely recycled because the process is usually not cost-effective. These non-recyclable wastes are usually disposed of in landfills, burned or used to generate electricity in waste-to-energy plants.
The initial success in plastic recycling is Vinyloop, an industrial process for separating PVC from other materials through the dissolution, filtration and separation of contaminants. Solvents are used in closed loops to elute PVC from waste. It is possible to recycle composite PVC waste, which is usually burned or put into a landfill. Vinyloop's recycled PVC based primary energy demand is 46 percent lower than conventionally produced PVC. The global warming potential is 39 percent lower. This is why the use of recycled materials leads to significantly better ecological results. This process is used after the 2012 London Olympics. Parts of temporary Buildings such as Water Polo Arena and Royal Artillery Barracks are recycled. In this way, PVC Policies can be met, which says that no PVC waste is left after the game ends.
In 1988, to help recycle disposable items, the US Plastic Industry Plastic Bottle Society of the United States designed a well-known scheme to mark plastic bottles with plastic types. Under this scheme, the plastic container is marked with a triangle of three "chasing arrows", which wrap the number indicating the plastic type:
- Polyethylene terephthalate (PET or PETE)
- High-density polyethylene (HDPE)
- Polyvinyl chloride (PVC)
- Low density polyethylene (LDPE)
- Polypropylene (PP)
- Polystyrene (PS)
- Other plastic types (see list below)
Representative polymer
Bakelite
The first plastics made of synthetic polymers are made from phenol and formaldehyde, with the first and inexpensive synthesis method invented in 1907, by Leo Hendrik Baekeland, a Belgian-born American born in New York state. Baekeland looks for insulating plates to coat the wires in electric motors and generators. He found that combining the phenol (OH 6 H 5 OH) and formaldehyde (HCOH) formed a sticky mass and later found that the material could be mixed with wood flour, asbestos, or slate dust to create a strong and fireproof "composite" material. The new materials tend to foam during synthesis, requiring Baekeland to build pressure vessels to force bubbles out and provide a smooth and uniform product, as it was announced in 1909, at the American Chemical Society meeting. Bakelite was originally used for electrical and mechanical components, becoming widely used in consumer goods and jewelry in the 1920s. Bakelite is a pure synthetic material, not derived from living matter. It is also an early thermosetting plastic.
Polystyrene
Uncompacted Polystyrene is a rigid, brittle, and inexpensive plastic that has been used to make similar plastic and knick-knacks. This is also the basis for some of the most popular "foaming" plastics, under the name of styrene foam or Styrofoam. Like most other foam plastics, foamed polystyrene can be produced in the form of "open cell", in which foam bubbles are interconnected, as in absorbent sponges, and "closed cells", where all bubbles are different, such as small balloons, such as foam insulation and devices flotation filled gas. In the late 1950s, high impact styrene was introduced, which is not fragile. He found many uses today as the substance of toy sculptures and novelties.
Polyvinyl chloride
Polyvinyl chloride (PVC, commonly called "vinyl") combines chlorine atoms. The C-Cl bonds in the backbone are hydrophobic and oxidant (and burning) resistant. PVCs are rigid, strong, heat and weatherproof, properties that recommend their use in devices for pipes, gutters, home fencing, enclosures for computers and other electronic equipment. PVC can also be softened with chemical processing, and in this form is now used for shrink-wrap, food packaging, and rain gear.
All PVC polymers are degraded by heat and light. When this happens, hydrogen chloride is released into the atmosphere and oxidation of the compound takes place. Since hydrogen chloride is ready to combine with water vapor in the air to form hydrochloric acid, polyvinyl chloride is not recommended for long-term silver archive storage, film or photographic paper (mylar is preferred).
Nylon
The plastics industry was revolutionized in the 1930s with the announcement of polyamide (PA), much better known by its trade name nylon . Nylon is the first pure synthetic fiber, introduced by DuPont Corporation at the 1939 World Exposition in New York City.
In 1927, DuPont embarked on a Fiber66 designated secret development project, under the direction of Harvard chemist Wallace Carothers and director of the chemistry department of Elmer Keizer Bolton. Carothers has been hired to undertake pure research, and he works to understand the molecular structure and the physical properties of new materials. He took the first few steps in the molecular design of the material.
His work leads to the discovery of synthetic nylon fibers, which are very powerful but also very flexible. The first application is to brush your teeth. However, Du Pont's real target is silk, especially silk stockings. Carothers and his team synthesized a number of different polyamides including polyamides 6.6 and 4.6, as well as polyesters.
DuPont takes twelve years and US $ 27 million to fix nylon, and to synthesize and develop industrial processes for mass manufacturing. With such a large investment, it is not surprising that Du Pont leaves little to promote nylon after it is introduced, creating a public sensation, or "nylon mania".
The Nylon mania suddenly ceased in late 1941 when the US entered World War II. The production capacity that has been built to produce nylon stockings, or just nylons, for American women is taken over to produce a large number of parachutes for brochures and paratroopers. After the war ended, DuPont again sold nylon to the public, engaging in another promotional campaign in 1946 that generated a greater predilection, sparking the so-called nylon riots.
Further, polyamides 6, 10, 11, and 12 have been developed based on monomers which are ring compounds; eg caprolactam. Nylon 66 is a material produced by condensation polymerization.
Nylon still remains an important plastic, and not just for use in fabrics. In the form of bulk is very wear resistant, especially if oil-impregnated, and so is used to build gears, plain bearings, valve seats, seals and because of good heat resistance, more and more for applications under the hood of the car, and other mechanical parts.
Poly (methyl methacrylate)
Poly (methyl methacrylate) ( PMMA ), also known as acrylic or acrylic glass and by trade name Plexiglas , Acrylite , Lucite , and Perspex among some others (see below), is a transparent thermoplastic often used in sheet forms as an alternative that is lightweight or breakable for glass. The same material can be used as casting resin, in ink and coating, and has many other uses.
Rubber
Natural rubber is an elastomer (elastic hydrocarbon polymer) originally derived from latex , a milky colloidal suspension found in special vessels in some plants. This is of direct use in this form (indeed, the first appearance of rubber in Europe is waterproof cloth with unvulcanized latex from Brazil). However, in 1839, Charles Goodyear invented vulcanised rubber; a form of natural rubber heated with sulfur (and some other chemicals), forming a cross link between the polymer chain (vulcanization), improving elasticity and endurance.
In 1851, Nelson Goodyear added a filler for natural rubber to form ebonite.
Synthetic Rubber
The first synthetic rubber was synthesized by Sergei Lebedev in 1910. In World War II, the natural rubber supply blockade from Southeast Asia caused an explosion in the development of synthetic rubber, especially styrene- butadiene rubber. In 1941, the annual production of synthetic rubber in the United States was only 231 tons which increased to 840,000 tons in 1945. In the space race and nuclear arms race, Caltech researchers experimented with synthetic rubber for solid fuel for rockets. Ultimately, all major military rockets and missiles will use synthetic rubber-based solid fuels, and they will also play an important part in civil space efforts.
See also
References
- An important part of this text comes from Introduction To Plastic v1.0/1 March 2001/greg goebel/public domain .
External links
- J. Harry Dubois's Collection of Plastic History, ca. 1900-1975 Archive Center, National American History Museum, Smithsonian Institution.
- Material Properties of Plastics - Mechanical, Thermal & amp; Electrical Properties
- A list of more than 600 plastics
- Plastic History Society
- Plastic History, Society of Plastics Industry
- "A brief history of plastics, natural and synthetic," from BBC Magazine
- Timeline of important milestones of plastic injection molding and plastics
Source of the article : Wikipedia
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