Page 222 - Engineered Interfaces in Fiber Reinforced Composites

204 En,qinerred interfaces in ,fiber reinforced composites

The first mechanism is thought to be particularly important for the ultrahigh
modulus polyethylene (UHMPE) fibers as the poor adhesive properties of
polyolefine are commonly associated with the presence of weak boundary layers
(Tissington et al., 1991). Fig. 5.23 compares the SEM microphotographs of
untreated and plasma treated (for 120 s) Tekmilon fiber surfaces, which display
dramatic changes in the surface morphology after treatment. The surf. clce cross-
linking of polyethylene fibers appears to start as soon as the fiber is exposed to
plasma, and its growth rate being a function of the discharge power and exposure
time. The increase in surface free energy is due to the introduction of polar groups
on the fiber surface during the treatment (Gao and Zeng. 1993a, b).

Fig. 5.23. Scanning electron microphotographs of (a) untreated and (b) plasma treated (120 s) Tekmilon
UHMWPE fibers. After Tissington et al. (1991). Reproduced by permission of Chapman & Hall.