Before PVC can be made into products, it has to be combined with a range of special additives. These additives can influence or determine a number of the products properties, namely; its mechanical properties, weather fastness, its colour and clarity and indeed whether it is to be used in a flexible application. This process is called compounding.
PVC's compatibility with many different kinds of additives is one of the materials many strengths and is what makes it such a highly versatile polymer. PVC can be plasticised to make it flexible for use in flooring and medical products. Rigid PVC, also known as PVC-U (The U stands for "unplasticised") is used extensively in building applications such as window frames.
The functional additives used in all PVC materials include heat stabilisers, lubricants, and in the case of flexible PVC, plasticisers. Optional additives, include a range of substances from processing aids, impact modifiers, thermal modifiers, UV stabilisers, flame retardants, mineral fillers, pigments, to biocides, and blowing agents for specific applications. The actual PVC polymer content in some flooring applications can be as low as 25% by mass, the remainder accounted for by additives.
Its compatibility with additives allows for the possible addition of flame retardants although PVC is intrinsically fire retardant because of the presence of chlorine in the polymer matrix.
There are several different types of additives for PVC:
Enhance the heat stability in moulding and heating operations.
Confer flexibility and certain other product qualities.
“Antioxidants” and “UV absorbents”
Prevent quality deterioration during use of plastic products.
“lubricants”, “pigments” and “fillers”
Give additional properties to plastic products.
After addition of these various additives, PVC is moulded and fabricated into durable products such as pipes for water supplies and sewers, electric cable coverings and construction materials, or agricultural films (agro-films) and medical devices, which have long been used as important materials supporting our society and daily life.