TENSILE PROPERTIES OF MIXTURES OF LINEAR POLYETHYLENE AND RANDOM ETHYLENE COPOLYMERS HAVING SIMILAR MOLECULAR-WEIGHTS

The stress-strain curves of mixtures of linear polyethylene and random ethylene-1-alkane copolymers have been studied. The molecular weights in each series were closely matched so that complications due to poly dispersity and chain length differences were avoided. The pertinent va riables were the composition, counit content, and crystallization mode . Comparison would be made of mixtures of the same molecular weight, d epending on whether on whether or not cocrystallization took place. Th e characters of the stress-strain curves were found to be different fo r these two different situations. The small-deformation properties, su ch as the initial modulus and yield stress, were found to depend only on the total core crystallinity irrespective of crystallization mode a nd composition. On the other hand, ultimate properties such as the dra w ratio break are very dependent on the phase structure of the system. In an important observation, which has other implications, it was fou nd that crystallinity levels and ultimate properties were the same in the mixture and pure copolymers when comparison was made at the same n ominal branch content.