What are important constitutents of plastics??
Constituents of Plastics:
The constituents of plastics are resin, plasticizer, filler, pigment and dye, lubricant and catalyst.Resin acts as binder for holding different constituents together.
Plasticizer (for workability) modifies plastic to impart desirable combination of strength, flexibility and toughness. Plasticizers, which are mostly liquids, are usually organic compounds or resins. Their addition is particularly necessary when the softening temperature of a resin is too high. Some of the examples of plasticisers are vegetable oils, camphor, esters of stearic and oleic acids, tributyl phosphate, tetrabutyl phosphate and triphenyl phosphate.
Filler (to produce bulk) is added up to 50 per cent of the mouldingmixture to increase the hardness, tensile strength, bond, opacity, finish and workability besides reducing the cost, shrinkage on setting, and brittleness of the final product. Some of the fillers are wood flour, asbestos fibers, mica, saw dust, ground cork, paper pulp, corn husk, carbon black, cotton fiber etc.
Pigment is added to achieve desired colour of the plastic and should be resistant to the action of sunlight or weathering.
Lubricant is used to make the moulding of plastic easier to prevent sticking of materials to the mould for a flawless finish e.g. soaps.
Catalyst is added only in the case of thermosetting plastics to accelerate the polymerization of fusible resin during moulding operation into cross-linked infusible form.
Fibers – added for strength and durability Blowing Agent Sodium bicarbonate and ammonium carbonate are sometimes added to plastics to produce porous articles.