5.6 Crystallisation of polymers
The major benefits of crystallisation of chain molecules to end users are:
since Tm > Tg, the maximum service temperatures are higher than with amorphous polymers;
above Tg , the modulus of a crystalline polymer is higher than that of an amorphous polymer owing to reinforcement and physical crosslinking of the amorphous matrix by the crystallites.
Both effects are evident by comparing the stress relaxation curves of atactic and isotactic PS of Figure 48. However, crystallisation morphology and kinetics differ from polymer to polymer as a result of structural and energetic factors.