The Blender

Title Page
History of PVC
Manufacture of PVC
Producing Chlorine
Producing Ethelyne
Producing PVC
Producing VCM
Disposing of PVC

Additives are blended with PVC to determine the properties of the PVC we want to form. These include; texture, colour, stability, mechanical and electrical properties, clarity and weather fastness.

The relevant additives are mixed with the polymer in a process called compounding which is carried out in one of two ways:

One method blends all the ingredients using an intensive high-speed mixer to form a 'dry blend' powder, which is then fed into the processing equipment. The second method blends the ingredients in either a high or low speed mixer and then the powder is transferred to a melt compounder. this produces a melt which, when cool, is cut into granules ready for processing.

A variety of processing methods such as extrusion, injection moulding, blow moulding and coating are then applied to the PVC compounds to form products.

Common/main additives are as follows:

  • plasticisers (make products flexible)
  • heat stabilisers (prevent PVC decomposing when heated)
  • lubricants (control its rate of flow when it is molten and prevents it from sticking to metal surfaces)
  • processing aids and impact modifiers (make plastic more workable or make the final article stronger)
  • fillers (make up half the weight of a PVC plastic article to increase profits)
  • colourants (organic dyes or inorganic pigments)
  • flame retardants (PVC is less flammable than most polymers but by adding a few % antimony oxide makes it even less so)

Other specialist additives are antistatic agents, biostabilisers and viscosity modifiers.

All the additives are tested for environmental compatibility and toxological safety before they are used.