Effect of solid-state stress induced reaction on morphology and structure of metallocene polyethylene

Metallocene-catalyzed polyethylene (mPE) powder was prepared through a mechanochemical reactor in solid state at ambient temperature. The changes of morphology and structure of mPE were investigated by SEM, FTIR, DSC, viscosimetry, GPC, WAXD, dynamic rheometer, and high pressure capillary rheometer methods. FTIR measurement illustrated that the branching degree of mPE increased after mechanochemical reaction. Combined with the dynamic rheological analysis, it was proved that the rupture and combination of macromolecular chain undergo strong shear resulted in the formation of long chain branches. X-ray diffraction analysis showed that the crystal form of mPE transferred from rhombic to monoclinic system partly, and the crystalline degree increased slightly in the initial mechanochemical reaction period. Viscometer test results exhibited that molecular weight of mPE dropped during the mechanochemical treatment. Rheology measurement indicated that the critical shear rate of the shark-skin failure enhanced and the extruded stands exhibited smooth face for the mPE after mechanochemical treatment. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1691-1699, 2013