Effect of variation in the chemical structure on the rate of crystallisation of polymers

Abstract

Seven linear polyesters having similar molecular weights
and closely related structures were prepared. The
crystallisation rates of these polyesters were measured by
using the Du Pont thermal analyzer and DSC cell. Additional
rate measurements were made using dilatometry. The
relative merits of the two techniques are discussed.

The results obtained by DSC and dilatometry were
analysed in terms of the Avrami equation using a computer
program. The variation in the Avrami integer n and its
possible significance are considered in detail.

Parameters which represented the readiness of a polymer
to crystallise, and the maximum crystallisation rates
obtainable were selected. These were used to compare the
crystallisation behaviour of the different polyesters. Chain
flexibility was found to be an important factor governing
nucleation. Crystallisation was inhibited by the presence of
bulky groups restricting chain movement.

Melting temperatures of the polymers were measured using
optical microscopy. An estimate of their thermodynamic
melting temperatures wags made using crystallisation half times.
The effect of polymer structure on melting temperature is
discussed.

Spherulite growth measurements were made wherever possible.
These results are related to the overall crystallisation rates.

X-ray powder photographs and fibre diagrams were
obtained. Results showed that crysallisation rates were not affected by crystal structure.

The degree of crystallinity of samples of some of the
polyesters was olttained from measurement of heats of fusion.
An explanation of the crystallinites obtainable in the
different polyesters is given.

Date of Award	1970
Original language	English