Potassium permanganate treatment produces a dramatic
change, as shown in Fig. 4. It can be seen that as-received UHMWPE
fibers show relatively smooth surface. After the surface treatment,
the highly developed cracks have now replaced the longitudinal
striations. The cracks are caused by the degradation of the molecule
chains on the fiber surface as a result of potassium permanganate
etching [20]. These cracks result in a great increase of the surface
area and, thus, provide more favorable conditions for various
physical and chemical interactions between fiber and NR. Of treated
UHMWPE fibers, the remarkable crack, into which rubber can
penetrate to produce a mechanical interlocking between fiber and
rubber matrix, is one of the most important factors in improving
the fiber/NR adhesion.