The concept polymer properties

The properties of materials can always be divided into three distinct, though inseparable, categories intrinsic properties, processing properties and product or article properties. Fig. 3.1 (Van Krevelen, 1967) gives a survey. It should be emphasised that these three categories of properties are strongly interrelated. Whereas intrinsic properties always refer to a substance, product properties refer to an entity they also depend on size and 

The intrinsic properties lend themselves to almost exact reproducible measurement. The Processing properties are combinations of some intrinsic properties that determine the possibility of processing materials and the efficacy of this operation. During processing a number of properties are added, e.g. form and orientation. It is the combination of certain intrinsic properties and the added properties that constitutes the product properties. 

As the actual material properties are anchored in the chemical and physical structure of the material, all intrinsic properties relate to a material with a distinct processing history. Usually the change in chemical structure during processing is small compared with the change in physical structure. 

In each of these phases the material is subject to changing temperatures, changing external and internal forces and varying retention times, all of which contribute to the ultimate structure. It is this fluctuating character of the conditions in processing which makes it so difficult to choose criteria for the processing properties. 

In order to find answers to the problems of processability and to bridge the gap between research data (i.e. the behaviour expected) and the behaviour in practice, usually simulation experiments are carried out. As regards processing, the simulation experiment has to approach actual practice as closely as possible. 

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