Polymer-2-OUT-OF-2.pdf

Vulcanization of rubber During 1839, Charles Good Year developed the method of vulcanization of rubber by which the properties of natural rubber can be improved to a large extent. Important Thermoplastics 1. Polyethylene Polyethylene is polymerised ethylene. Ethylene is colorless gas at...

Vulcanization of rubber During 1839, Charles Good Year developed the method of vulcanization of rubber by which the properties of natural rubber can be improved to a large extent. Important Thermoplastics 1. Polyethylene Polyethylene is polymerised ethylene. Ethylene is colorless gas at ordinary temperature. It is prepared in the lab by dehydration of ethyl alcohol at 160°C with concentrated H2SO4. Important Thermoplastics Two types of polyethylenes are available: LDPE (Low density polyethylene) is produced by using high pressure methods (1050-2000 kgf/cm2) using free radical initiator, and HDPE (high density polyethylene) is produced by using low pressure methods (31 kgf/cm2) using ionic catalysts Important Thermoplastics 2. Polypropylene It is obtained by polymerizing propylene in presence of Ziegler-Natta Catalyst. It is used for packing of pharmaceutical and cosmetic products, for making sterilizable hospital equipment, washing machine parts, pipes, TV, radios, moulded luggage, colorful furniture etc. Important Thermoplastics 3. Polyvinyl Chloride Vinyl chloride is the monomer for PVC and the monomer is produced by direct addition of HCl to acetylene at 60°C- 80°C. It is the most widely used plastic. It has high rigidity and chemical resistance but brittle, so, its use is mainly in making cables, water hoses, rain coats, pipes of petroleum industry. Important Thermoplastics 4. Polytetrafluoroethylene (TEFLON) It is obtained by polymerization of water-emulsion of tetrafluoro ethylene, under pressure and in presence of benzoyl peroxide as catalyst. Non-stick cookware coatings are made of TEFLON. It can be used for making gaskets, pump parts, tank linings, non- lubricating bearings and to make non- reactive coating. Important Thermoplastics 5. Polyurethanes These are a varied range of crosslinked polymers made from two liquids—a polyol and an isocynate. It is used as insulating material in refrigerators. Due to its spongy nature, it is used for making pillows and matresses. Important Thermosetting 1. Epoxy resin Epoxy resins are obtained from a poly condensation of epichlorohydrin with polyphenols or polyalcohols. The epoxy resins are used as the major constituents of adhesives in paint industry and as insulator in electrical industry. Important Thermosetting 2. Polyester Terylene is the British name of Dacron, which is obtained by condensation of ethylene glycol and terephthalic acid. Polyester is mostly used for making synthetic fibers which are used for making garments for men, women and children. It can be blended with wool and used for making carpets, blankets, upholsteries, quilts etc. Important Thermosetting 3. Silicones Silicones have alternate silicon-oxygen bonds and organic radicals attached to the silicon atoms. They are used as damping in cosmetics, silicone - glass laminates for high temperature application, etc. Synthetic Rubbers Artificially produced rubber-like polymers which can be stretched to at least twice its length and on releasing the stress, it returns to its original shape and size. SBR is similar to natural rubber in processing character and also as finished product. It is mainly used for tke manufacture of tyres. It is also used as soles and other components of shoes, for insulating wires and cables, as adhesives and lining for vessels MISCELLANEOUS POLYMERS 1. Laminate. It is obtained by joining two or more layers of solid materials with the help of an adhesive. (a) Plywood. Odd numbers of layer of wood (0.5-10 mm thick) are bonded such that grains of alternate layers are at right angles to each other (cross-laminate). Plywood is used for making railway coack, cabinets, false-ceilings and in other house building purposes. MISCELLANEOUS POLYMERS (b) Laminated Plastics. Paper, cloth, asbestos fibre, glass, metal etc., are impregnated with thermosetting resin like phenol-formaldehyde or urea- formaldehyde solution in solvent. They are used for electrical and insulating materials, pump parts etc. They are also used for decorative purposes on table tops and wall panellings etc. MISCELLANEOUS POLYMERS (c) Laminated glasses. Two glass sheets are joined by a plastic sheet in between to form laminated glass. For transparency, polyvinyl-butyl resin can be used as adhesive. Bullet proof or splinter proof laminated glass is obtained by curing the laminates in an oven under heat and pressure. Conducting Polymers Conducting polymers are made by special powders and are classified as: (a) pi-electrons conducting polymer (b) Conducting element-filled polymer (c) Inorganic polymer (d) Doped-conducting polymer (e) Blended conducting polymer. Conducting Polymers Conducting polymers are used for making (i) button cells (ii) pkotovoltaic devices (iii) sensors and (iv) biomedical devices. References Brown L, Holme T. (2011). Chemistry for Engineering Students. Mary Finch. https://ionlights.keybase.pub/books/Chemistry%20for%20Engineering%20Stud ents%2C%202e.pdf Jain J. (2015). Engineering Chemistry. Dhanpat Rai. https://pdfcoffee.com/engineering-chemistry-by-jain-amp-jain-pdf-free.html WAKAS