Concerning elongation at break vs temperature relationships, 226 a maximum
at 20°C to 60°C above Tg of the soft segment is obtained. However, in the
working range of most elastomers, elongation at break decreases with increasing
temperature. The upper temperature limit for practical use of segmented elastomers
is related to the softening of the hard segment. Bonart has tried to
measure heat distortion temperature (THD) and relate it to the structure of the
hard segment. 52'227 THD is measured by measuring the change of length of the