rystallization behavior of ultrahigh molecular weight polyethylene polymerized with HE--1 type catalyst has been studied by means of small angle X--rayscattering (SAXS)

wide angle X--ray diffraction(WAXD) and differential scanningcalorimetry(DSC). It was found that crystallinity

long periods

crystallite regionthickness and amorphous region thickness formed in dilute solution are independentof molecular weight and are related with crystallization temperature. If crystalswere obstained from melt crystallization. Its long periods are independent of mo-lecular weight

but related with crystallization temperature and time. Crystallinity and crystallite region thickness decrease with molecular weight increase. Amorphous regions increase with molecular weight and the melting temperature increases with molecular weight. The nascent crystals have higher melting points than those from melt

but the long period of nascent crystals has not been found.