Abstract
Melt viscosities of polyethylene fractions were studied. The fractions of the polyethylene polymerized by a slurry process using the Phillips type chromium oxide catalyst in a poor solvent showed a peculiar melt flow behavior compared to the usual linear polyethylene fractions. The former showed a considerably higher melt viscosity and stronger extent of non-Newtonian behavior than the latter in the high molecalar weight region, above 5×104.
Nevertheless, there is no difference between the two series of fractions in the solution behavior, such as the relation between the inherent viscosity and the weight average molecular weight Mw, or the radius of gyration and Mw. In addition, the existence of microgels which may be a cause of the high viscosity of the polymer melt was not proved.
From the fact that the polyethylene fractions in question have smaller terminal vinyl groups determined by the IR spectrum than the usual linear fractions at the same number average molecular weight Mn, together with the results cited above, it was presumed that they include star type molecules by a few percents having long chain branches centered by the very fine particle of the catalyst.
