Ultra-drawing of low molecular weight polyethylene — ultra-high molecular weight polyethylene blend films prepared by gelation/crystallization from semi-dilute solutions

Abstract

Greatest drawability was studied for blend films with branched low molecular weight polyethylene (B-LMWPE) and ultra-high molecular weight polyethylene (UHMWPE) prepared by gelation/crystallization from solutions. The morphology of B-LMWPE–UHMWPE dry gel film and its deformation mechanism were mainly estimated by using differential scanning calorimeter, small-angle X-ray scattering, wide-angle X-ray diffraction and solid-state 13C NMR. The detailed analysis was carried out for the blend films including large amounts of B-LMWPE. As a result, it was found that the UHMWPE and B-LMWPE were crystallized separately from the mixed solution. The greatest drawability was attributed to a suitable number of entanglements between UHMWPE crystal lamellae that are highly oriented with their large flat faces parallel to the film surface. These entanglements play an important role to transmit the drawing force as intermolecular cross-links and ensured smooth crystal transition of UHMWPE from a folded to a fibrous. In this process, large amount of B-LMWPE is thought to be almost independent of the ultra-drawing behavior of UHMWPE, since the domains of UHMWPE and B-LMWPE within the blend have no interaction and B-LMWPE crystallites take almost a random orientation.