ON THE STRUCTURE OF ULTRA-HIGH-MOLECULAR-WEIGHT POLYETHYLENE GELS

Gel-crystallized ultra-high molecular weight polyethylene samples have been studied by transmission electron microscopy (TEM) and differenti al scanning calorimetry. The microstructure of the gels was investigat ed by substitution of the solvent by methacrylate monomers which were subsequently cured by ultraviolet radiation at low temperature. TEM im ages of RuO4-stained thin sections showed a network of lamella crystal s in which the links were formed by local contacts of the crystal surf aces. Electron spectroscopic imaging yielded carbon concentration prof iles across the width of isolated crystals. Annealing of the dried gel s above T(alpha) illustrated a high mobility of the polyethylene chain s within the crystal above the alpha-transition and well below the mel ting point. Long lamellae became decorated by shorter and thinner crys tallites which appear to be grown perpendicular on the surface of the long ones.