Ageing of materials is a widespread phenomenon,occurring in all areas of modern life,particularly in relation to technical problems associated for example with building of machines.The fact that it such a common phenomena explains why it attracts increasing attention in the literature both from the point of view of discovering the mechanisms of the ageing process and assessing its effect on the properties of constructional materials.The gradual and inevitable increase in the demand for polymeric materials,which are often irreplaceable in the construction of machines,tools and everyday products,means that research studies have for many years been directed towards explaining the complex mechanisms of ageing(refs.1 and 2),determining its effect on the properties-mainly physical and chemical-of this type of materials(refs.3 and 4)and assessing the influence of processing conditions on the occurrence of this phenomenon(refs.5 and 6).The concept of ageing of polymeric materials covers the whole range of physical and chemical changes occurring in their structure and causing a change in their properties during processing and also in the course of their storage or use.
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