Some morphological aspects of polyolefins

A study was made of the crystallisation of three commercially available linear low-density polyethylenes from the melt by quenching in iced water. Solvent extraction and nitric acid etching techniques were used to show the variation in the degree of branching with respect to molecular weight, and the almost total rejection of branches from the crystalline core. Linear polyethylene crystallised under the influence of an extensional flow field, as exists in traditional melt spinning of fibres, was also studied, with a view to assessing the effect of a molten metal coolant on the spinline. A metal spinning rig operating in conjuction with a molten metal reservoir was designed and built at Southampton, using a standard extruder to inject polymer through a die into the reservoir base. High degrees of crystalline orientation were observed, correlating with improved physical properties of the spun filaments. (D82613)