difference between natural and synthetic fibers

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From Wikipedia

Synthetic fiber

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.

History

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:

Specialty synthetic fibers include:

Other synthetic materials used in fibers include:

Modern fibers that are made from older artificial materials include:

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

Industry structure

During the last quarter of 20th century, Asian share of global output of synthetic fibers doubled to 65 per cent.


Synthetic rubber

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.

History

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.

In 1909, a team headed by Fritz Hofmann, working at the Bayer laboratory in Elberfeld, Germany, also succeeded in polymerizing methyl isoprene, the first synthetic rubber.

Scientists in England and Germany developed alternative methods for creating isoprene polymers from 1910–1912.

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.

The company Thiokol applied their name to a competing type of rubber based on ethylene dichloride which was commercially available in 1930.

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 resin

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.


Optical fiber

An optical fiber or optical fibre is a thin, flexible, transparent fiber that acts as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics. Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher bandwidths (data rates) than other forms of communication. Fibers are used instead of metal wires because signals travel along them with less loss and are also immune to electromagnetic interference. Fibers are also used for illumination, and are wrapped in bundles so they can be used to carry images, thus allowing viewing in tight spaces. Specially designed fibers are used for a variety of other applications, including sensors and fiber lasers.

Optical fiber typically consists of a transparent core surrounded by a transparent cladding material with a lower index of refraction. Light is kept in the core by total internal reflection. This causes the fiber to act as a waveguide. Fibers which support many propagation paths or transverse modes are called multi-mode fibers (MMF), while those which can only support a single mode are called single-mode fibers (SMF). Multi-mode fibers generally have a larger core diameter, and are used for short-distance communication links and for applications where high power must be transmitted. Single-mode fibers are used for most communication links longer than 1050|sp=us|m|ft.

Joining lengths of optical fiber is more complex than joining electrical wire or cable. The ends of the fibers must be carefully cleaved, and then spliced together either mechanically or by fusing them together with heat. Special optical fiber connectors are used to make removable connections.

History

Fiber optics, though used extensively in the modern world, is a fairly simple and old technology. Guiding of light by refraction, the principle that makes fiber optics possible, was first demonstrated by Daniel Colladon and Jacques Babinet in Paris in the early 1840s. John Tyndall included a demonstration of it in his public lectures in London a dozen years later. Tyndall also wrote about the property of total internal reflection in an introductory book about the nature of light in 1870: "When the light passes from air into water, the refracted ray is bent towards the perpendicular... When the ray passes from water to air it is bent from the perpendicular... If the angle which the ray in water encloses with the perpendicular to the surface be greater than 48 degrees, the ray will not quit the water at all: it will be totally reflected at the surface.... The angle which marks the limit where total reflection begins is called the limiting angle of the medium. For water this angle is 48°27', for flint glass it is 38°41', while for diamond it is 23°42'."

Practical applications, such as close internal illumination during dentistry, appeared early in the twentieth century. Image transmission through tubes was demonstrated independently by the radio experimenter Clarence Hansell and the television pioneer John Logie Baird in the 1920s. The principle was first used for internal medical examinations by Heinrich Lamm in the following decade. In 1952, physicist Narinder Singh Kapany conducted experiments that led to the invention of optical fiber. Modern optical fibers, where the glass fiber is coated with a transparent cladding to offer a more suitable refractive index, appeared later in the decade. Development then focused on fiber bundles for image transmission. The first fiber optic semi-flexible gastroscope was patented by Basil Hirschowitz, C. Wilbur Peters, and Lawrence E. Curtiss, researchers at the University of Michigan, in 1956. In the process of developing the gastroscope, Curtiss produced the first glass-clad fibers; previous optical fibers had relied on air or impractical oils and waxes as the low-index cladding material. A variety of other image transmission applications soon followed.

In the late 19th and early 20th centuries, light was guided through bent glass rods to illuminate body cavities. Alexander Graham Bell invented a 'Photophone' to transmit voice signals over an optical beam.

Jun-ichi Nishizawa, a Japanese scientist at Tohoku University, also proposed the use of optical fibers for communications in 1963, as stated in his book published in 2004 in India. Nishizawa invented other technologies which contributed to the development of optical fiber communications, such as the graded-index optical fiber as a channel for transmitting light from semiconductor lasers. Charles K. Kao and George A. Hockha


From Encyclopedia

Polymers, Natural Polymers, Natural

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 180° in cellulose, and 120° 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 –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 α -helix and the β -pleated sheet. An α -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 α -helix is the basic structural unit of hair and wool, which are bundles of polypeptides called α -keratins. The helical structure imparts some elasticity to hair and wool. The polypeptides in silk, on the other hand, are β -keratins with the β -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.


From Yahoo Answers

Question:Please also give me an example of each.

Answers:a natural polymer occurs in nature, like cellulose or starch a synthetic polymer is synthesized in a laboratory, like nylon or polyethylene

Question:

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...

Question:what are some of the advantages of synthetic fibres over natural fibres? what are some of the advantages of natural fibre over synthetic fibres?

Answers:natural fibers include cotton, wool, silk and linen. each has its own characteristics. Cotton absorbs well Wool is warm, even when wet Synthetic fibers include nylon, rayon, polyester, dacron and a few others Less ironing is needed to keep wrinkle-free Deeper colors are available stronger fibers do not rot in weather do not shrink

Question:please give me detailed information

Answers:I will assume youre talking about clothing. natural fibers like wool and cotton are: -fire resistant. polymer based fibers will melt -environmentally sound. they do not require petroleum to produce. -more breathable, as they have an affinity for water. however, they are: -generally more expensive, since synthetics can easily be mass produced. -susceptible to pests such as moths and silverfish -can shrink in aggressive washing

From Youtube

The Diameters of Natural Hairs and Synthetic Fiber. Part 1/2 :The diameters of natural hairs and synthetic fiber are analyzed. We provide SEM (Scanning Electron Microscopy) images of natural hairs: Kolinsky sable, Siberian Squirrel, Hog bristle and the synthetic fiber. We find scales on the surfaces of natural hairs. Synthetic fiber does not have these scales. We provide nice images of the Hog bristle "flags". Hog bristle hair has the largest diameter, then goes Kolinsky hair, and finally, Siberian squirrel which is the softest and has the smallest diameter. The diameter of the synthetic fiber is close to the diameter of Kolinsky hair, however at the tip it drops dramatically. This sometimes leads to the formation of "hooks" at the tips of the synthetic fiber which can ruin the brush. Research by Artist Supply Source, Inc. Visit us at www.ArtistSupplySource.com

The Diameters of Natural Hairs and Synthetic Fiber. Part 2/2 :The diameters of natural hairs and synthetic fiber are analyzed. We provide SEM (Scanning Electron Microscopy) images of natural hairs: Kolinsky sable, Siberian Squirrel, Hog bristle and the synthetic fiber. We find scales on the surfaces of natural hairs. Synthetic fiber does not have these scales. We provide nice images of the Hog bristle "flags". Hog bristle hair has the largest diameter, then goes Kolinsky hair, and finally, Siberian squirrel which is the softest and has the smallest diameter. The diameter of the synthetic fiber is close to the diameter of Kolinsky hair, however at the tip it drops dramatically. This sometimes leads to the formation of "hooks" at the tips of the synthetic fiber which can ruin the brush. Research by Artist Supply Source, Inc. Visit us at www.ArtistSupplySource.com