The setting angle of extended chain linear polyethylene

Abstract

The unit cell parameters and the setting angle have been estimated for a series of linear polyethylene specimens crystallized at pressures from atmospheric to 6 kbar. Slight variations in unit cell parameters occur, however, significant differences can be discerned in the setting angles as a function of crystallization pressure. It is suggested that the setting angle of extended chain crystals is the equilibrium value for the crystal and that the setting angle is influenced by the presence of folded chains and the structure of the fold surface. Such a hypothesis would account for the spread in published values of setting angles for specimens crystallized both at atmospheric pressure and under strain.