Study On The Improvement Of UV Resistant Properties Of PPS Fibers Modified By TiO₂/benzotriazole

Polyphenylene Sulfide （PPS） is a linear semi-crystalline polymer with excellent high-temperature resistance, chemical resistance, flame resistance and dimensional stability. With the continuous improvement of quality of PPS resins, the applications of PPS fiber have expanded a lot, not only in industrial use but also in daily usages. As a result, the photo stability of PPS fiber must be paid enough attentions.After several years of study, our group has successfully prepared the PPS filaments with good performance. During the research of PPS fiber formation, we found that whether the imported or domestic PPS production’s color changed from yellow to dark after the UV irradiation. In fact, the color gets darker and darker with longer irradiation. At the same time, the fiber becomes brittle and the break strength decreases significantly. These changes will greatly limit the applications of PPS fiber.In this paper, the PPS photo-aging phenomenon has been studied. Molecular structure, crystalline properties and dynamic mechanical properties of PPS changed after different time of UV irradiation. Results showed that molecular structure changed significantly after the irradiation. Molecular chain fractured and small molecules were formed, while the crystallinity of the sample decreased. At the same time, a cross-linked structure has formed which made sample’s glass temperature （Tg） higher. As found in this study, the cross-linking of PPS molecular structure is dominating at first. On the other hand, as irradiation goes, the molecular fracture gradually becomes dominating. Nano TiO₂ and benzotriazole have good absorption effects on 200-400 nm wavelengths which can effectively reduce the damage of UV irradiation on polymers. 1.5%wt benzotriazole, 1.5%wt nano TiO₂ and of 1.5%wt of the benzotriazole/nano TiO₂ mixtures were added to the PPS matrix respectively, in order to study the photo stabilizers’ impact on the PPS fiber processing and usage performance. From the results of thermal degradation properties, crystalline properties, rheological properties, and chemical resistance of modified PPS fiber, we demonstrated that the selected photo stabilizers did not destroy the high temperature resistance and chemical resistance of PPS fiber. By adding the photo stabilizers, the complex viscosity of PPS compounds was smaller than that of the pure PPS at low shear rate. With the increasing of shear rate, the descend rate of PPS compounds complex viscosity declined. However, at high shear rate, the complex viscosity of PPS became higher than that of the pure PPS. The PPS compounds trended to be viscous rheological behavior after adding the photo stabilizers. The photo stabilizers promoted the nuclearation, changed the supramolecular structure of PPS fiber, thereby, affected fiber tensile properties.The significant changing of color from yellow to dark and the great mechanical properties decreasing of PPS fiber after UV irradiation restrict the applications of this high performance product. By comparing the color change degrees and the mechanical properties descent degrees of pure PPS fiber and PPS/photo stabilizers modified fiber before and after UV irradiation, the influence photo stabilities were study. The results showed that the color change of modified PPS fiber, which the selected nano TiO2/ benzotriazole compounds added, decreased significantly after UV irradiation. In addition, this study found that by the help of photo stabilizers the break strength of modified PPS fiber increased significantly. After the UV irradiation, the break strength of modified PPS fiber also declined, but the decline ratio was smaller than the pure PPS fiber’s. Based on these two observations, the modified PPS fibers maintain better mechanical properties. As a conclusion, the photostability of PPS fiber improved.