Weathering and Other Properties

From a study done in 1977 on the ageing of about 35 high polymers and organic glasses, it was concluded that ageing occurs in broad temperature ranges below the Tg [10], (i.e., for PVC from +70 to -50 °C and for polycarbonate (PC) from +150 to -100 °C). 

Permeability, toxicity, flammability are also some of the important properties of polymers which must be considered during their structural use. 

The properties of polymers may be improved by the presence of appropriately selected additives. Types of additives and their purposes vary and the exact proportions and nature of the additives need some experimentation. Commercial plastics are mixtures of more polymers along with a variety of additives such as plasticisers, thermal stabilisers, flame retardants, processing lubricants and fillers. Specific applications or processing requirements depend on the exact formulation [1, 8]. 

In some cases, certain properties of a polymer can be enhanced by blending it with another polymer or by copolymerisation with a suitable monomer pair. Additives may be mixed with the polymer before processing by a variety of techniques, such as dry blending, extrusion, compounding, and other methods discussed in Chapter 8. 

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