The effect of water on polymer matrix and composite wear

Previous studies have demonstrated increased in vitro wear of composite after long-term water exposure. The increased wear effect was not clearly related to debonding of the filler from the matrix, resulting in accelerated loss of filler particles. The hypothesis tested in this experiment was that the changes in in vitro three-body wear of a composite following water storage are caused by changes in the wear resistance of the polymer matrix.

In the in vitro wear test used, a specimen wheel was rotated against an antagonist wheel in a slurry of millet seed and water. Specimens were fabricated of composite and polymer matrix only. Specimens were wear tested after 1 wk of ambient temperature dry storage and after 14, 20, and 26 mon of water storage at 37 degrees C.

The wear of the composite significantly increased (23%) during the 26 mon of water storage. The wear of the polymer specimens increased slightly; however, the increase was not statistically significant.

Analyses of the data using a series model for the wear of a composite indicated that the increase in wear of the composite was not due to changes in the wear resistance of the polymer matrix. Instead, the increased composite wear was more likely due to increases in the dislodgment rate of filler particles and the wear rate of the filler itself.