Abstract
The extended-chain crystal structure of the UHMWPE fibers prepared by melt spinning method was studied with WAXD, DSC and SEM. At draw ratio (DR) values higher than 24, double melting peaks were observed from the DSC thermograms, the corresponding temperatures being 137.1–142°C and 142–145°C, respectively. With the increase of DR values, the lengths in a and b axis of the unit cell shortened, and the unit cell remained orthorhombic even if the DR values increased to 60. At DR values lower than 24, the crystallinity and orientation degree of the UHMWPE fibers affected the tensile strength of fibers markedly. At DR values were higher than 24, the abundantly produced extended-chain crystals mainly dominated the improvement of tensile strength of the UHMWPE fibers.