Induced crystallisation of flexible polymeric molecules by pressure and stress

INDUCED CRYSTALLISATION OF FLEXIBLE POLYMERIC MOLECULES BY PRESSURE AND STRESS 

In practice, many fabrication processes take place under non-isothermal, non-quiescent and high-pressure conditions. Mechanical deformation and pressure can enhance the crystallisation as well as the crystal morphology, by aligning the polymer chains. This leads to pressure-induced crystallisation and to flow-induced or stress-induced crystallisation, which in fact is the basis for fibre melt-spinning (see Sect. 19.4.1) 

Important investigations in this field have been made by Wunderlich (1964/1972) and Basset (1973/1974). The effect of high pressure on the crystallisation process is threefold  

A high pressure enhances the formation of crystal modifications with packing that are as dense as possible. Since extended chains have denser packing than folded chains, an increase of pressure is favourable for chain extension. 

A high pressure raises the temperature of melting. For large pressure variations the change in the melting temperature is given by the Simon equation 

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