1) Binders – Binders hold the other constituents together during manufacture. eg. Natural or synthetic resins or cellulose derivatives, etc

Binders influence the properties of plastics. The type of treatment during moulding operation also depends upon binders.

If a binders used has comparatively low molecular weight, then plastic article gets moulded easily & vice versa.

2) Fillers or Extenders – Fillers impart better tensile strength, hardness, finish, workability, opacity, etc to the plastic material. eg. Organic fillers – Wood flour, cotton pulp, paper pulp, carbon black, graphite, powdered rubber, etc.

In organic fillers – asbestos, powdered mica, silicate clays, talc, Zn & Pb oxides, Cd & Ba sulphides, Al, Fe, Cu, metal in powdered form, etc.

They reduce shrinkage & brittleness. They also reduce cost of the plastic per unit weight.

3) Plasticizers – These help to increase the plasticity of the plastics. eg. Vegetable oil, camphor, esters of stearic, tri-phenyl phosphate, diethyl phthalate, etc

These help to reduce the forces of intermolecular attraction & thereby increases tendency of sliding or moving. Thus the plastics which are plasticized possess high percentage of flexibility. They are essentially used in thermo softening plastics.

4) Pigments / Dyes – These imparts desired colors to the plastic. eg. Organic dyestuffs & inorganic pigments

The coloring matter used in plastics should be resistance to the action of sunlight.

5) Catalysts or accelerators – These are used to increase the rate of polymerization of fusible resin binder to form cross linked infusible form during moulding operations. eg. Hydrogen peroxide, benzoyl peroxide, metallic oxides, etc

6) Lubricants – lubricants help during moulding operations, especially during low or room temperature moulding. eg. Soaps or esters of fatty acids such as oleic & stearic acids or waxes.

The use of lubricants imparts flawlessness, & glossy finish to the plastic products. They form a layer between they article & mould. This layer prevents the plastic material from sticking to the surface of the mould, & thereby facilitating the moulding operations.

7) Stabilizers - Stabilizers helps to improve thermal stability of the plastic. eg. Salt of lead, white lead, lead chromate, red lead, & transparent moulding compounds are stearates of lead, cadmium & barium, etc.

These are required especially in the processing stage for plastic, which have tendency to decompose or change their colours at moulding temperatures.