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THERMOSETTING PLASTICS AND ITS TYPES

Thermosetting plastics are made from chains which have been linked together, referred to as cross-linked. These have a three dimensional network of molecules and will not soften when heated. They are practically insoluble, fireproof and usually hard and brittle. These plastics cannot be  reused.

EPOXY RESINS :

EPOXY RESIN is one of the new comers to the plastic field. It is cured or cross-linked by the addition of a hardener. Epoxies have excellent chemical resistance and electrical insulating properties. Their working temperature is from 150*C to 260*C with fillers additives.

Coatings made from these resins combine the properties of  toughness; flexibility, adhesion and chemical resistance to a degree not found in other coating materials. Epoxy adhesives are now finding applications in aircraft, automobiles and in the home.

While epoxy adhesive are well known, these plastics are also used as casting for pipe fittings , electrical and other equipment. These are also used in both low-pressure and high pressure laminates such as printed-circuit boards, boat bodies , etc. 


epoxy resins


AMINO RESINS :

The two important groups of amino resins are the urea-resins and melamine-formaldehyde resins. Both are used as adhesives in making plywood and melamine is laminated with cloth to make table and counter tops. The melamine can be molded into very hard, scratch-resistant dinnerware , business machine housings, electric switch cover plates, radio cabinets, etc. The urea compounds are less water resistant but better electrical insulators. 


Amino Resins


PHENOLICS : 

Phenol and Formaldehyde combine in the presence of  a  catalyst to produce phenolic resins. These are hard, brittle, heat-resistant thermosets widely known in the trade name of Bakelite. They are inexpensive, excellent insulator and have heat-distortion temperatures up to 180*C and working temperatures up to 260*C. They are often used with a wide variety of fillers.

These may be molded or cast and they are also used as coatings and in adhesive applications. 


Phenolics


SILICONES :

Silicones are chemical hybrid, a cross between organic and inorganic materials. Silicone base polymers possess a combination of  properties that make them valuable for a large group of  industrial products including greases, oils , adhesives , resins and rubber compounds.

Special silicone fluids are fast becoming an ingredient in cosmetics, The silicones are also useful in furniture, auto, shoe, glass and silver polishes. Silicone resins can be processed by extrusion, transfer molding, casting and compression molding. 


Silicones


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