Abstract
The distributions of short-chain branching in some tvnical commercial high pressure polyethylenes were investigated by determining the degree of branching of their fractions. On the fractions of tubular-type polyethylenes fractionated with respect to molecular weight, the degree of branching was found to be lower at higher molecular weight fraction, while on those of vessel-type polyethylenes there was only small molecular weight dependency. These results are closely related to the wide distribution of polymerization temperature or pressure in tubular process.
The distributions of degree of branching within above mentioned fractions, which were obtained by measuring the degree of branching of the sub-fractions refractionated with respect to degree of branching, did not differ markedly between samples. However, in the high molecular weight fractions of vessel-type polyethylenes an anomalous behavior was observed and this seems to suggest the existence of long-chain branchings of complex structure in these fractions.
