Best Results From Wikipedia Yahoo Answers Encyclopedia Youtube
Synthetic rubber is any type of artificial elastomer, invariably a polymer. An elastomer is a material with the mechanical (or material) property that it can undergo much more elasticdeformation under stress than most materials and still return to its previous size without permanent deformation. Synthetic rubber serves as a substitute for natural rubber in many cases, especially when improved material properties are required. Nowadays synthetic rubber is used a great deal in printing textile. In this case it is called rubber paste. In most cases titanium dioxide is used with copolymerization and volatile matter in producing such synthetic rubber for textile use. Moreover this kind of preparation can be considered to be the pigment preparation based on titanium dioxide.
Comparison of natural and synthetic rubber
Natural rubber coming from latex is mostly polymerized isoprene with a small percentage of impurities in it. This limits the range of properties available to it. Also, there are limitations on the proportions of cis and transdouble bonds resulting from methods of polymerizing natural latex. This also limits the range of properties available to natural rubber, although addition of sulfur and vulcanization are used to improve the properties.
Synthetic rubber can be made from the polymerization of a variety of monomers including isoprene (2-methyl-1,3-butadiene), 1,3-butadiene, chloroprene (2-chloro-1,3-butadiene), and isobutylene (methylpropene) with a small percentage of isoprene for cross-linking. These and other monomers can be mixed in various desirable proportions to be copolymerized for a wide range of physical, mechanical, and chemical properties. The monomers can be produced pure and the addition of impurities or additives can be controlled by design to give optimal properties. Polymerization of pure monomers can be better controlled to give a desired proportion of cis and transdouble bonds.
In 1879, Bouchardt created one form of synthetic rubber, producing a polymer of isoprene in a laboratory.
The expanded use of motor vehicles, and particularly motor vehicle tires, starting in the 1890s, created increased demand for rubber.
Scientists in England and Germany developed alternative methods for creating isoprene polymers from 1910â€“1912.
The Russian scientist Sergei Vasiljevich Lebedev created the first rubber polymer synthesized from butadiene in 1910. This form of synthetic rubber provided the basis for the first large-scale commercial production, which occurred during World War I as a result of shortages of natural rubber. This early form of synthetic rubber was again replaced with natural rubber after the war ended, but investigations of synthetic rubber continued. Russian American Ivan Ostromislensky did significant early research on synthetic rubber and a couple of monomers in the earlier 1900s.
Political problems that resulted from great fluctuations in the cost of natural rubber led to the enactment of the Stevenson Act in 1921. This act essentially created a cartel which supported rubber prices by regulating production (see OPEC), but insufficient supply, especially due to wartime shortages, also led to a search for alternative forms of synthetic rubber.
By 1925 the price of natural rubber had increased to the point that many companies were exploring methods of producing synthetic rubber to compete with natural rubber. In the United States, the investigation focused on different materials than in Europe, building on the early laboratory work of Nieuwland.
Studies published in 1930 written independently by Lebedev, the American Wallace Carothers and the German scientist Hermann Staudinger led in 1931 to one of the first successful synthetic rubbers, known as neoprene, which was developed at DuPont under the direction of E.K. Bolton. Neoprene is highly resistant to heat and chemicals such as oil and gasoline, and is used in fuel hoses and as an insulating material in machinery.
In 1935, German chemists synthesized the first of a series of synthetic rubbers known as Buna rubbers. These were copolymers, meaning the polymers were made up from two monomers in alternating sequence. The rubber designated GRS (Government Rubber Styrene), a copolymer of butadiene and
Synthetic resins are materials with a property of interest that is similar to natural plant resins: they are viscous liquids that are capable of hardening permanently. Otherwise, chemically they are very different from the various resinous compounds in secreted by plantss (see resin for discussion of the natural products).
The sythetics are of several classes. Some are manufactured by esterification or soaping of organic compounds. Some are thermosetting plastics in which the term "resin" is loosely applied the reactant or product, or both. "Resin" may be applied to one of two monomers in a copolymer (the other being called a "hardener", as in epoxy resins). For those thermosetting plastics which require only one monomer, the monomer compound is the "resin." For example, liquid methyl methacrylate is often called the "resin" or "casting resin" while it is in the liquid state, before it polymerizes and "sets." After setting, the resulting PMMA is often renamed acrylic glass, or "acrylic." (This is the same material called Plexiglas and Lucite).
Types of synthetic resins
The classic variety is epoxy resin, manufactured through polymerization-polyaddition or polycondensation reactions, used as a thermoset polymer for adhesives and composites. Epoxy resin is two times stronger than concrete, seamless and waterproof. Accordingly, it has been mainly in use for industrial flooring purposes since the 1960s. Since 2000, however, epoxy and polyurethane resins are used in interiors as well, mainly in Western Europe.
Synthetic casting "resin" for embedding display objects in Plexiglass/Lucite (PMMA) is simply methyl methacrylate liquid, into which a polymerization catalyst is added and mixed, causing it to "set" (polymerize). The polymerization creates a block of PMMA plastic ("acrylic glass") which holds the display object in a transparent block.
Another synthetic polymer sometimes called by the same general category, is acetal resin. By contrast with the other synthetics, however, it has a simple chain structure with the repeat unit of form -[CH2O]-.
Ion exchange resins are used in water purification and catalysis of organic reactions. See also AT-10 resin, melamine resin. Certain ion exchange resins are also used pharmaceutically as bile acid sequestrants, mainly as hypolipidemic agents, although they may be used for purposes other than lowering cholesterol.
A large category of resins, which constitutes 75% of resins used, is the unsaturated polyester resins.
Synthetic fibers are the result of extensive research by scientists to improve upon naturally occurring animal and plantfibers. In general, synthetic fibers are created by forcing, usually through extrusion, fiber forming materials through holes (called spinnerets) into the air, forming a thread. Before synthetic fibers were developed, artificially manufactured fibers were made from cellulose, which comes from plants. These fibers are called cellulose fibers.
Synthetic fibers account for about half of all fiber usage, with applications in every field of fiber and textile technology. Although many classes of fiber based on synthetic polymers have been evaluated as potentially valuable commercial products, four of them - nylon, polyester, acrylic and polyolefin - dominate the market. These four account for approximately 98 per cent by volume of synthetic fiber production, with polyester alone accounting for around 60 per cent.
The first artificial fiber, known as artificial silk, became known as viscose around 1894, and finally rayon in 1924. A similar product known as cellulose acetate was discovered in 1865. Rayon and acetate are both artificial fibers, but not truly synthetic, being made from wood. Although these artificial fibers were discovered in the mid-nineteenth century, successful modern manufacture began much later (see the dates below).
Nylon, the first synthetic fiber, made its debut in the United States as a replacement for silk, just in time for World War II rationing. Its novel use as a material for women's stockings overshadowed more practical uses, such as a replacement for the silk in parachutes and other military uses.
Common synthetic fibers include:
- Rayon (1910) (artificial, not synthetic)
- Acetate (1924) (artificial, not synthetic)
- Nylon (1939)
- Modacrylic (1949)
- Olefin (1949)
- Acrylic (1950)
- Polyester (1953)
- Carbon fiber (1968)
Specialty synthetic fibers include:
- Vinyon (1939)
- Saran (1941)
- Spandex (1959)
- Vinalon (1939)
- Aramids (1961) - known as Nomex, Kevlar and Twaron
- Modal (1960's)
- Dyneema/Spectra (1979)
- PBI (Polybenzimidazole fiber) (1983)
- Sulfar (1983)
- Lyocell (1992)
- PLA (2002)
- M-5 (PIPD fiber)
- Zylon (PBO fiber)
- Vectran (TLCP fiber) made from Vectra LCP polymer
- Derclon used in manufacture of rugs
Other synthetic materials used in fibers include:
- Acrylonitrile rubber (1930)
Modern fibers that are made from older artificial materials include:
- Glass Fiber is used for:
- industrial, automotive, and home insulation (Fiberglass)
- reinforcement of composite and plastics
- specialty papers in battery separators and filtration
- Metallic fiber (1946) is used for:
In the horticulture industry synthetics are often used in soils to help the plants grow better. Examples are:
- expanded polystyrene flakes
- urea-formaldehyde foam resin
- polyurethane foam
- phenolic resin foam
During the last quarter of 20th century, Asian share of global output of synthetic fibers doubled to 65 per cent.
Condensation polymers are any kind of polymers formed through a condensation reaction, releasing small molecules as by-products such as water or methanol, as opposed to addition polymers which involve the reaction of unsaturated monomers. Types of condensation polymers include polyamides, polyacetals and polyesters.
Condensation polymerization, a form of step-growth polymerization, is a process by which two molecules join together, resulting loss of small molecules which is often water. The type of end product resulting from a condensation polymerization is dependent on the number of functional end groups of the monomer which can react.
Monomers with only one reactive group terminate a growing chain, and thus give end products with a lower molecular weight. Linear polymers are created using monomers with two reactive end groups and monomers with more than two end groups give three dimensional polymers which are crosslinked.
Dehydration synthesis often involves joining monomers with an -OH (hydroxyl) group and a freely ionized -H on either end (such as a hydrogen from the -NH2 in nylon or proteins). Normally, two or more different monomers are used in the reaction. The bonds between the hydroxyl group, the hydrogen atom and their respective atoms break forming water from the hydroxyl and hydrogen, and the polymer.
Nylon is another common condensation polymer. It can be manufactured by reacting di-amines with carboxyl derivatives. In this example the derivative is a di-carboxylic acid, but di-acyl chlorides are also used. Another approach used is the reaction of di-functional monomers, with one amine and one carboxylic acid group on the same molecule:
The carboxylic acids and amines link to form peptide bonds, also known as amide groups. Proteins are condensation polymers made from amino acid monomers. Carbohydrates are also condensation polymers made from sugar monomers such as glucose and galactose.
Condensation polymerization is occasionally used to form simple hydrocarbons. This method, however, is expensive and inefficient, so the addition polymer of ethene (polyethylene) is generally used.
Condensation polymers, unlike addition polymers, may be biodegradable. The peptide or ester bonds between monomers can be hydrolysed by acid catalysts or bacterial enzymes breaking the polymer chain into smaller pieces.
The word "polymer" means "many parts" (from the Greek poly, meaning "many," and meros, meaning "parts"). Polymers are giant molecules with molar masses ranging from thousands to millions. Approximately 80 percent of the organic chemical industry is devoted to the production of synthetic polymers, such as plastics, textiles fibers, and synthetic rubbers. A polymer is synthesized by chemically joining together many small molecules into one giant molecule. The small molecules used to synthesize polymers are called monomers. Synthetic polymers can be classified as addition polymers, formed from monomer units directly joined together, or condensation polymers, formed from monomer units combining such that a small molecule, usually water, is produced during each reaction. Polymers are widely found in nature. The human body contains many natural polymers, such as proteins and nucleic acids. Cellulose, another natural polymer, is the main structural component of plants. Most natural polymers are condensation polymers, and in their formation from monomers water is a by-product. Starch is a condensation polymer made up of hundreds of glucose monomers, which split out water molecules as they chemically combine. Starch is a member of the basic food group carbohydrates and is found in cereal grains and potatoes. It is also referred to as a polysaccharide, because it is a polymer of the monosaccharide glucose. Starch molecules include two types of glucose polymers, amylose and amylopectin, the latter being the major starch component in most plants, making up about three-fourths of the total starch in wheat flour. Amylose is a straight chain polymer with an average of about 200 glucose units per molecule. A typical amylopectin molecule has about 1,000 glucose molecules arranged into branched chains with a branch occurring every 24 to 30 glucose units. Complete hydrolysis of amylopectin yields glucose; partial hydrolysis produces mixtures called dextrins, which are used as food additives and in mucilage, paste, and finishes for paper and fabrics. Glycogen is an energy reserve in animals, just as starch is in plants. Glycogen is similar in structure to amylopectin, but in a glycogen molecule a branch is found every 12 glucose units. Glycogen is stored in the liver and skeletal muscle tissues. Cellulose is the most abundant organic compound on Earth, and its purest natural form is cotton. The woody parts of trees, the paper we make from them, and the supporting material in plants and leaves are also mainly cellulose. Like amylose, it is a polymer made from glucose monomers. The difference between cellulose and amylose lies in the bonding between the glucose units. The bonding angles around the oxygen atoms connecting the glucose rings are each 180Â° in cellulose, and 120Â° in amylose. This subtle structural difference is the reason we cannot digest cellulose. Human beings do not have the necessary enzymes to break down cellulose to glucose. On the other hand, termites, a few species of cockroaches, and ruminant mammals such as cows, sheep, goats, and camels, are able to digest cellulose. Chitin, a polysaccharide similar to cellulose, is Earth's second most abundant polysaccharide (after cellulose). It is present in the cell walls of fungi and is the fundamental substance in the exoskeletons of crustaceans, insects, and spiders. The structure of chitin is identical to that of cellulose, except for the replacement of the OH group on the C-2 carbon of each of the glucose units with an â€“NHCOCH3 group. The principal source of chitin is shellfish waste. Commercial uses of chitin waste include the making of edible plastic food wrap and cleaning up of industrial wastewater. All proteins are condensation polymers of amino acids. An immense number of proteins exists in nature. For example, the human body is estimated to have 100,000 different proteins. What is amazing is that all of these proteins are derived from only twenty amino acids. In the condensation reaction whereby two amino acids become linked, one molecule of water forming from the carboxylic acid of one amino acid and the amine group of the other is eliminated. The result is a peptide bond; hence, proteins are polypeptides containing from approximately fifty to thousands of amino acid residues. The primary structure of a protein is the sequence of the amino acid units in the protein. The secondary structure is the shape that the backbone of the molecule (the chain containing peptide bonds) assumes. The two most common secondary structures are the Î± -helix and the Î² -pleated sheet. An Î± -helix is held together by the intramolecular hydrogen bonds that form between the N-H group of one amino acid and the oxygen atom in the third amino acid down the chain from it. The Î± -helix is the basic structural unit of hair and wool, which are bundles of polypeptides called Î± -keratins. The helical structure imparts some elasticity to hair and wool. The polypeptides in silk, on the other hand, are Î² -keratins with the Î² -sheet structure, in which several protein chains are joined side-to-side by intermolecular hydrogen bonds. The resulting structure is not elastic. Nucleic acids are condensation polymers. Each monomer unit in these polymers is composed of one of two simple sugars, one phosphoric acid group, and one of a group of heterocyclic nitrogen compounds that behave chemically as bases. Nucleic acids are of two types: deoxyribonucleic acid (DNA ), the storehouse of genetic information, and ribonucleic acid (RNA), which transfers genetic information from cell DNA to cytoplasm, where protein synthesis takes place. The monomers used to make DNA and RNA are called nucleotides. DNA nucleotides are made up of a phosphate group, a deoxyribose sugar, and one of four different bases: adenine , cytosine , guanine , or thymine . The nucleotides that polymerize to produce RNA differ from DNA nucleotides in two ways: they contain ribose sugar in place of deoxyribose sugar and uracil instead of thymine. Natural rubber is an addition polymer made up of thousands of isoprene monomer repeating units. It is obtained from the Hevea brasiliensis tree in the form of latex. The difference between natural rubber and another natural polymer, gutta-percha (the material used to cover golf balls), is the geometric form of the polyisoprene molecules. The CH2 groups joined by double bonds in natural rubber are all on the same sides of the double bonds (the cis configuration), whereas those in gutta-percha are on opposite sides of the double bonds (the trans configuration). This single structural difference changes the elasticity of natural rubber to the brittle hardness of gutta-percha. see also Deoxyribonucleic Acid; Nucleic Acids; Polymers, Synthetic; Proteins. Melvin D. Joesten Atkins, Peter W. (1987). Molecules. New York: W. H. Freeman. Joesten, Melvin D., and Wood, James L. (1996). The World of Chemistry, 2nd edition. Fort Worth, TX: Saunders College.
polymer , chemical compound with high molecular weight consisting of a number of structural units linked together by covalent bonds (see chemical bond ). The simple molecules that may become structural units are themselves called monomers; two monomers combine to form a dimer, and three monomers, a trimer. A structural unit is a group having two or more bonding sites. A bonding site may be created by the loss of an atom or group, such as H or OH, or by the breaking up of a double or triple bond, as when ethylene, H 2 C[symbol]CH 2 , is converted into a structural unit for polyethylene , -H 2 C-CH 2 -. In a linear polymer, the structural units are connected in a chain arrangement and thus need only be bifunctional, i.e., have two bonding sites. When the structural unit is trifunctional (has three bonding sites), a nonlinear, or branched, polymer results. Ethylene, styrene, and ethylene glycol are examples of bifunctional monomers, while glycerin and divinyl benzene are both polyfunctional. Polymers containing a single repeating unit, such as polyethylene, are called homopolymers. Polymers containing two or more different structural units, such as phenol-formaldehyde, are called copolymers. All polymers can be classified as either addition polymers or condensation polymers. An addition polymer is one in which the molecular formula of the repeating structural unit is identical to that of the monomer, e.g., polyethylene and polystyrene . A condensation polymer is one in which the repeating structural unit contains fewer atoms than that of the monomer or monomers because of the splitting off of water or some other substance, e.g., polyesters and polycarbonates (see illustration) . Many polymers occur in nature, such as silk, cellulose , natural rubber , and proteins . In addition, a large number of polymers have been synthesized in the laboratory, leading to such commercially important products as plastics, synthetic fibers, and synthetic rubber. Polymerization, the chemical process of forming polymers from their component monomers, is often a complex process that may be initiated or sustained by heat, pressure, or the presence of one or more catalysts.
From Yahoo Answers
Answers:a natural polymer occurs in nature, like cellulose or starch a synthetic polymer is synthesized in a laboratory, like nylon or polyethylene
Answers:Natural synthetic are obtained from nature, they have less durabality, they are less strong, some times they have to be processed. Artificial synthetic are man and machine made, have have high durability, they are strong, they are already processed while manufacturing and are available in variety of colours...
Answers:Alkanes, also known as paraffins, are chemical compounds that consist only of the elements carbon (C) and hydrogen (H) (i.e., hydrocarbons), wherein these atoms are linked together exclusively by single bonds A polymer is a large molecule (macromolecule) composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties and purposes.
Answers:polyester in clothes, polystyrene in foam packaging polycarbonate like in Nalgene bottles proteins are polypeptides, a polymer of amino acids. DNA is a polymer of nucleic acids.