Insight into the Excellent Tribological Performance of Highly Oriented Poly(phenylene sulfide)

Achieving low friction and wear of poly(phenylene sulfide) (PPS) without using fillers or blending is a challenging task, but one of considerable practical importance. Here we describe how neat PPS with high tribological performance is achieved by manipulating processing parameters (pressure, flow and temperature). The key to achieving high tribological performance is comparatively high molecular chain orientation, realized in neat PPS, at high shear rates and low pressure. The friction coefficient and wear rate are as low as ∼0.3 and ∼10−6 mm3·N−1·m−1, respectively, which break the record for neat PPS. These values are even better than those for PPS-based blends and comparable to PPS composites. Further studies show, for the first time, that wear rate decreases exponentially with increasing molecular chain orientation, prompting us to revise the classical Archard’s law by including the effect of molecular chain orientation. These findings open the possibility of using neat PPS in highly demanding tribological applications.