Deformation of Ultrahigh Molecular Weight Polyethylene Precursor Fiber: Crystal Slip with or without Melting

Temperature effects on deformation behaviors of extracted ultrahigh molecular weight polyethylene (UHMWPE) precursor fibers are studied with the in situ synchrotron radiation wide-angle X-ray scattering technique (WAXS) during tensile deformation at temperatures from 25 to 130 degrees C. The structural and mechanical evolution behaviors during tensile deformation can be divided into four temperature regions with boundaries located at temperatures of alpha(1) and alpha(II) relaxations and the onset of melting, respectively, which reveal that the deformation behaviors of polymer crystals are determined by the interplay between intrinsic structural dynamic or chains mobility and external stress field. Irrespective of temperature, yield and strain-softening proceed via partial melting while crystal slip via cutting crystal planes occurs in the strain-hardening zone. Finally we construct morphological diagrams containing crystallinity, crystal size, and orientation in temperature strain space, which may serve as a roadmap for UHMWPE fibers processing.