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.
relevant additives are mixed with the polymer in a process called
compounding which is carried out in one of two ways:
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.
variety of processing methods such as extrusion, injection moulding,
blow moulding and coating are then applied to the PVC compounds
to form products.
additives are as follows:
(make products flexible)
(prevent PVC decomposing when heated)
(control its rate of flow when it is molten and prevents it from
sticking to metal surfaces)
aids and impact modifiers (make plastic more workable or make
the final article stronger)
(make up half the weight of a PVC plastic article to increase
(organic dyes or inorganic pigments)
(PVC is less flammable than most polymers but by adding a few
% antimony oxide makes it even less so)
specialist additives are antistatic agents, biostabilisers and viscosity
the additives are tested for environmental compatibility and toxological
safety before they are used.