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.