Growth of Bulky Extended Chain Single Crystals of Polyethylene

Crystallization process of fractionated polyethylene (PE) about 10 µm thick from liquid at high pressure was observed by optical microscope and X-ray method. The needle-like crystal obtained was unchanged in the shape except for appearing of striation through the hexagonal-orthorhombic transition and it gave spotty X-ray pattern corresponding to the a * -b * plane of reciprocal lattice of hexagonal and orthorhombic form. The direction of its long axis coincided to that of [010] in the hexagonal form and to that of [010], [110] or [\=110] in the orthorhombic form. These results suggests that the needle-like crystal was composed of rather bulky single crystals of µm dimension as compared with the usual polymer single crystals of 100 A thick and that the formation of the hexagonal needle-like crystal corresponds to that of extended chain crystal of PE.