Abstract:At present, the tensile strength of UHMWPE fibers prepared by melt spinning was lower to gel spun fibers. In this paper, the microstructures of the melt spun and gel spun UHMWPE fibers were studied by XRD,DSC and SAXS. The results are shown, compared with UHMWPE fiber produced by gel spun, the melt spun UHMWPE fiber has lower tensile strength primarily because it contains a small volume of extended-chain crystallites. Its macromolecular chains do not stretch fully. Thus, monoclinic crystals inside the UHMWPE fibers produced by melt spinning have a low degree of orientation, and its structure is not as compact as that of fiber produced by gel spun. The fundamental reason for this result is that the effective draw ratio of the melt-spun UHMWPE fiber is not high.