SURFACE MODIFICATION OF UHMWPE FIBERS

Ultrahigh molecular weight polyethylene (UHMWPE) fibers have a high sp ecific strength, high specific modulus, and outstanding toughness, but their poor adhesive properties has limited their use for composite ma terial applications. In this research, the effects of chemical etching on the surface chemistry and topography have been explored using chro mic acid, potassium permanganate, and hydrogen peroxide etching. The s mooth surface observed on the as-received fiber was rich in ether and/ or hydroxyl oxygen. This smooth surface resulted from the presence of an outer layer, a weak boundary layer, that was removed by all the etc hants. A fibrillar structural hierarchy was revealed beneath this oute r layer and the fiber was relatively unchanged by further etching. Chr omic acid, the strongest etchant studied, produced a rough and oxidize d UHMWPE surface with both ether and carbonyl oxygen. The combination of outer layer removal, roughness, and changes in oxygen bonding helps explain the improved adhesion on chromic acid etching in spite of the reduction in surface oxygen. Neither hydrogen peroxide nor potassium permanganate etching roughened or oxidized the surface to a great exte nt and neither yielded improved adhesion. (C) 1994 John Wiley & Sons, Inc.