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Unformatted text preview: CHAPTER 7- NYLON AND ARAMID FIBERS- Nylon: manufactured fiber in which fiber-forming substance is long chain synthetic polyamide in which LESS than 85% of amide linkages attached directly to two aromatic rings FTC- Aramids- polyamides where 85% or MORE of amide linkages are attached to two aromatic rings- Nylon first synthetic produce; Wallace Carothers chemist working for DuPont Co. in Delaware NYLON- Nylon 66 and nylon 6 are isomers (each polymer contains same elements by weight but polymers molecules are arranged differently); such differences in structure cause differences in fiber properties- Generic name nylon proposed in 1938 by DuPont o Considered Delawear (for state in which DuPont labs located) & Duparooh ( for DuPont pulls a rabbit out of a hat)- Production grown in volume of past several decades but share of synthetic mkt. declined as other synthetics such as polyester and olefin have grown Manufacture- Nylon 66 synthesized from adipic acid and hexamethylene diamine o 6 carbons atoms in each molecule of adipic acid & 6 carbon atoms in each molecule of hexamethylene diamine o Sometimes Nylon 6,6- Nylon 6 made form caprolactam o 6 carbons in caprolactam- Polymerization of Nylon 66 o 1) preparation of nylon salt (compound but not polymer of adipic acide and hexamethylene diamine); salt prepared first to ensure proper ratio of acid and amine in subsequent polymerization step o 2) condensation polymerization takes place in air-free atmos; water (which is split off during polymerization) allowed to escape from reacting tanktitanium dioxide added in this step o 3) synthesized nylon extruded directly as fibers **in earlier processes, molten polymer extruded from tank as ribbon; quenched in cold water; then broken into smaller nylon chips- Polymerization of Nylon 6 o Method 1 Caprolactum melted, heated, and filtered under high pressure; during this condensation polymerization takes place o Method 2 Water in amt. of 10% of weight of caprolactam added; then water & caprolactam heated to high temp, steam escapes, and polymerization takes place- Spinning o Both are melt spun66 has higher melting pt (500 F) than 6 (430 F) o Melted polymer delivered form extruder or directly from polymerizer and passed through filter to remove any impurities o Fed to metering pump that delivers measured amt of polymer to pack (consists of small filter & spinneret) o As exiting from spinneret, molten filaments enter chimney where theyre air cooled and simultaneously stretched to orient molecules o Spin finish coated onto fiber Complex mix of oil lubs emulsified in water together with additional materials such as wetting agents, antistatic agents, and adhesives Lubricates fibers for subsequent processing and disperses static electrical charges that would interfere with yarn formation Eventually washed from fabric- Drawing o Fiber wound onto bobbin then stretched to 400-600% of orig. length because not particularly strong at Fiber wound onto bobbin then stretched to 400-600% of orig....
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- Fall '08