MORPHOLOGY OF CHEMICALLY CROSS-LINKED ULTRAHIGH MOLECULAR-WEIGHT POLYETHYLENE

Morphological characterization of chemically crosslinked ultrahigh mol ecular weight polyethylene was performed by differential scanning calo rimetry and scanning electron microscopy. The lamellar thickness of na scent UHMWPE inferred from DSC endotherms showed a very broad distribu tion, which was reduced significantly after melting and recrystallizin g in DSC. Peroxide crosslinking further reduced the lamellar thickness distribution compared to uncrosslinked samples. After gamma-irradiati on, a slowly cooled peroxide-free sample showed a greater increase in lamellar thickness distribution. Examination of the morphology of free ze-fractured surfaces by SEM showed that a slowly cooled peroxide-free UHMWPE exhibited a rougher fracture while chemically crosslinked samp les showed a smoother fracture. After compression molding at 300 degre es C for 2 h, the grain boundaries between particles disappeared for a ll UHMWPE samples, indicating a complete fusion of the original flakes . (C) 1998 John Wiley & Sons, Inc.