The force-elongation curves and key tensile parameters of a set of polyethy
lenes were studied over the temperature range from -100 degrees C to their
respective melting temperatures, at a fixed strain rate. The polymers chose
n possessed a diverse molecular architecture and constitution. They were cr
ystallized in such a manner as to generate a wide range in crystallinity le
vels and supermolecular structures. Unique to this work are accompanying di
latometric studies. These enabled the changing level of crystallinity with
temperature to be monitored. The force-elongation curves that were obtained
varied in a systematic manner with the chain structure and deformation tem
perature. The yield stresses of all the polymers were very similar to one a
nother in the region of the glass transition temperature. However, they div
erged at elevated temperatures, depending on the chain structure, linear or
branched, and the level of crystallinity. The change in the ultimate prope
rties, the draw ratio, lambda(B), after break a nd the true ultimate tensil
e strength, with deformation temperature could be correlated with the chang
ing level of crystallinity. The temperature dependence of these properties
are strongly dependent on molecular weight and, except for the very highest
molecular weights, a maximum is observed. Possible mechanisms that govern
the ultimate properties are presented and discussed. The temperature depend
ence of the yield stress could not be correlated with the dislocation theor
y that has been developed to describe yielding. (C) 1998 Chapman & Hall.