Vulcanization and Thermoplastics Overview

Study Notes

In 1839, Charles Goodyear discovered vulcanization, a process that significantly improves the properties of natural rubber.

Polyethylene: Polymerised ethylene, a colorless gas produced by dehydrating ethyl alcohol at 160°C with concentrated H2SO4.
- LDPE (Low-density polyethylene): Produced using high-pressure methods (1050-2000 kgf/cm2) with free radical initiators.
- HDPE (High-density polyethylene): Produced using low-pressure methods (31 kgf/cm2) with ionic catalysts.
Polypropylene: Obtained by polymerizing propylene in the presence of Ziegler-Natta Catalyst. Applications include packaging for pharmaceuticals and cosmetics, sterilizable hospital equipment, washing machine parts, pipes, TVs, radios, molded luggage, and colorful furniture.
Polyvinyl Chloride (PVC): The most widely used plastic, made by polymerizing vinyl chloride, which is produced by directly adding HCl to acetylene at 60°C-80°C. Known for its high rigidity and chemical resistance, but brittle. Used in cables, water hoses, raincoats, petroleum industry pipes.
Polytetrafluoroethylene (TEFLON): Obtained by polymerizing a water-emulsion of tetrafluoroethylene under pressure and in the presence of benzoyl peroxide as a catalyst. Used in non-stick cookware coatings, gaskets, pump parts, tank linings, non-lubricating bearings, and non-reactive coatings.
Polyurethanes: A varied range of crosslinked polymers created from two liquids - a polyol and an isocyanate. Used as insulating material in refrigerators, pillows, mattresses due to its spongy nature.

Epoxy Resin: Obtained from the polycondensation of epichlorohydrin with polyphenols or polyalcohols. Used as the major constituent of adhesives in the paint industry and as an insulator in the electrical industry.
Polyester: Terylene (British name for Dacron) is produced by condensing ethylene glycol and terephthalic acid. Primarily used in synthetic fibers for garments and can be blended with wool for carpets, blankets, upholsteries, and quilts.
Silicones: Contain alternating silicon-oxygen bonds with organic radicals attached to silicon atoms. Used in cosmetics for damping, silicone-glass laminates for high-temperature applications.

Artificially produced rubber-like polymers capable of stretching to at least twice their length and returning to their original shape and size after stress release.
SBR (Styrene Butadiene Rubber): Similar in processing and finished product characteristics to natural rubber. Mainly used in tire manufacture and also in shoe soles, other shoe components, wire and cable insulation, adhesives, and vessel linings.

Laminate: Formed by joining two or more layers of solid materials using an adhesive.
- Plywood: Consists of odd numbers of wood layers (0.5-10 mm thick) bonded with the grain of alternate layers at right angles (cross-laminate). Applications include railway coaches, cabinets, false ceilings, and other house building purposes.
- Laminated Plastics: Paper, cloth, asbestos fiber, glass, metal, etc., are impregnated with thermosetting resins like phenol-formaldehyde or urea-formaldehyde solutions in solvent. Used in electrical and insulating materials, pump parts, and decorative purposes on table tops and wall panelings.
- Laminated Glasses: Two glass sheets are joined by a plastic sheet in between. Polyvinyl-butyl resin can be used for transparency. Bullet-proof or splinter-proof laminated glass is obtained by curing the laminates in an oven under heat and pressure.