Effect of Higher-Order Structure on Swelling Property in Toluene for Polyphenylene Sulfide

Polyphenylene sulfide (PPS) is a crystalline polymer with excellent properties such as high heat resistance, high strength, and high stability against solvent. PPS will not be degraded, even if it is exposed to gasoline fuel, diesel fuel, and alcohol fuel such as bio-ethanol. Because of these distinguishing properties, PPS is applied to many automobile parts around fuel system. In this paper, higher-order structure of PPS that influences the swelling property in toluene is elucidated by measuring the crystallinity. In the wide-angle X-ray scattering (WAXS) method, the negative relationship was observed in the wide range of the swelling amount (from 0.2 to 9 wt%). Before and after the swelling test of PPS in toluene for 700 hours at 60°C, the almost same scattering patterns were obtained in the WAXS method. The result shows the infiltration of toluene into the crystalline phase of PPS does not occur. In the small-angle X-ray scattering patterns, the peak position was unchanged even after the swelling test, although the half-width became larger. The result shows that the infiltration of toluene into the amorphous phase between the lamellar layers occurs.