Oriented Crystallization of Polyethylene at High Pressure from Flowed Melt

In the course of the study of polymer crystallization at high pressure, oriented crystallization of extended chain crystals of polyethylene were examined. Molten polyethylene were extruded into a die at a few hundred atm, and follwed by crystallization by high pressure application above 3000 atm. Resulting sample shows chain orientation to extruded direction. Thick lamella nearly a few thousand angstrom, which are typical feature of high pressure crystallization, were observed to be stacked parallel each other. In spite of favorable condition for crystals to grow to chain direction, remarkable growth to normal direction to them were also observed.