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MHT-CET : Chemistry Entrance Exam

MHT - CET : Chemistry - Synthetic Fibres Know More


All synthetic fibres are prepared by the process of polymerisation. They are long, chain-like molecules. Later on, they are subjected to spinning which involves procedures like melt, dry or wet. This involves pumping molten polymer through spinnerets.

  • Nylon: This was the first truly synthetic fibre, developed because of the research work carried out by Wallace H. Carothers of Dupont company. Nylon is commonly produced from hexamethylene diamine and adipic acid.
    Nylon is a popular plastic moulding powder and bristle material. It is stronger than any natural fibre and has a wet strength of 80 - 90%. Nylon's high tenacity has made it an important material in parachute fabrics and related items. The term "NYLON" is derived from
    New York and London as the fibre it was first introduced in these cities.
  • Dacron: Dacron is a polyester fibre, the condensation product of dimethyl terepthalate and ethylene glycol. Its polymerisation is carried out at high temperature under vacuum. The reaction releases methanol and a polymer chain containing 80 benzene rings is formed. The material formed is melt spun. The filaments are stretched out four times their original size. It is well suited for knit fabrics, such as sweaters, socks, men's summer suits, etc.
  • Saran: Saran is a co-polymer of vinyl chloride and vinylidene chloride. It is prepared by mixing the two monomers with catalyst and then heating. Colour is then added. The co-polymer is then heated, extruded at 180C, air-cooled and stretched. Saran is resistant to mildew, bacterial and insect attack, which makes it suitable for insect screens. It is chemical-resistant, which makes it useful as filter-cloth resistant. It is widely used in automobile upholstery and homes for furnishing purposes.
  • Viscose Rayon: Viscose is the largest man-made fibre and its manufacture consumes more than 20% of the industrial chemical output. High tenacity viscose yarn is mainly used in tyre cords and fabrics for tyres, hose and belting. The difference in strength between ordinary and high tenacity viscose is conditioned by the amount of viscose and acetate blended with wool in carpet manufacture.
  • Finishing Processes for Fabrics: Three important finishes consist of flame proofing or fire retarding, mildew or rot-proofing and water repellency. Temporary flame proofing of cellulosic material is achieved by application of ammonium salts, borax or boric acid. Mildew proofing of cellulosic fabric is obtained through use of organic and inorganic compounds. The commonly used materials include chlorinated phenols, valicylanilide and organic mercurial compounds. To produce water repellant finishes, special quartenary ammonium compounds are heat-treated on the fibre.
    Shrink-proofing of wool employs chlorinating process, especially for socks, shirts, knitting yarns and blankets. Another method for shrink-proofing woven fabrics is adding melamine formaldhyde. Thermosetting resins are widely used to impart crease or wrinkle resistance to cellulosic fibres. Commonly used products include urea formaldehyde and melanine formaldehyde resins. The fabric is treated with precondensates together with condensation catalyst. Many other special treatments for fabrics, including moth-proofing, resiliency, stiffening, softening, eliminating electrostatic charge during processing, sizing, lubricating, etc. are also carried out.

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