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 differential scanning calorimetry. The microstructure of the gels was investigated by substitution of the solvent by methacrylate monomers which were subsequently cured by ultraviolet radiation at low temperature. TEM images of RuO4-stained thin sections showed a network of lamella crystals in which the links were formed by local contacts of the crystal surfaces. Electron spectroscopic imaging yielded carbon concentration profiles across the width of isolated crystals. Annealing of the dried gels above T(alpha) illustrated a high mobility of the polyethylene chains within the crystal above the alpha-transition and well below the melting point. Long lamellae became decorated by shorter and thinner crystallites which appear to be grown perpendicular on the surface of the long ones.