Effect of Cooling Temperature on Crystalline Behavior of Polyphenylene Sulfide/Glass Fiber Composites

Poly (phenylene sulfide) (PPS) is a super engineering plastic that has not only excellent rigidity and high chemical resistance but also excellent electrical insulation properties; therefore, it can be applied as an electronic cover or an overheating prevention component. This plastic has been extensively applied in the manufacture of capacitor housing as, in addition to being a functional and lightweight material, it has a safety feature that can block the electrical connection between the electrolyte inside and outside the capacitor. Moreover, the fabrication of PPS composites with high glass fiber (GF) content facilitates the development of lightweight and excellent future materials, which widens the scope of the application of this polymer. However, the crystallinity and mechanical properties of PPS/GF composites have been found to vary depending on the cooling temperature. Although extensive studies have been conducted on the influence of cooling temperature on the crystalline behavior of PPS-based composites, there has been limited research focused particularly on PPS/GF composites for capacitor housing applications. In this study, to apply PPS/GF composites as film capacitor housings, specimens were prepared via injection molding at different cooling temperatures to investigate the composites' tensile, flexural, and impact energy absorption properties resulting in increases in mechanical properties at high cooling mold temperature. Fracture surface analysis was also performed on the fractured specimens after the impact test to confirm the orientation of the GF and the shape of the micropores. Finally, the crystallinity of the composites increased with higher cooling temperatures due to the extended crystallization time.

Thermal Aging Effects on the Mechanical Behavior of Glass-Fiber-Reinforced Polyphenylene Sulfide Composites

In this article, the thermal aging behavior of polyphenylene sulfide (PPS) composites, reinforced by 20% glass fibers (GFs), in thermal aging temperatures ranging from 85 to 145 °C was studied. Tensile and bending properties and color changes in the thermally aged samples were investigated. The results showed that thermal aging at this temperature range resulted in the degradation of mechanical properties. Both the tensile and flexural strength of the GF/PPS composites were significantly reduced after thermal aging at 145 °C. Decreased strength and brittle fracture were observed because thermal aging at high temperatures resulted in the deterioration of the interfaces between the GFs and PPS matrix. The degradation of the mechanical properties of the composite samples can be reflected by the color change, which means that the mechanical properties of the GF/PPS composite samples under thermal aging are predictable using color change analysis.

Effect of isothermal heat treatment on crystallinity, tensile strength and failure mode of CF/PPS laminate

The present work concentrates on the crystallinity, tensile strength and failure mode of CF/PPS laminate subjected to isothermal heat treatment of different temperatures and time periods. Results show that in the range of 100–210°C and 1–3 hours, with the increase of heat treatment temperature and time, both crystallinity and tensile strength of CF/PPS laminate increase firstly then decrease. Under the condition of 150°C-2 hours treatment, the CF/PPS has the optimal crystallinity level of 65.3% and the optimal tensile strength with a value of 718.2 MPa. Compared with the as-received specimen without heat treatment, the crystallinity and tensile strength have been increased by 46.4% and 15.3%, respectively. A laser confocal microscope has been used to observe and analyze the fracture morphologies of the specimens, results show that the failure modes of the specimens under conditions of 100°C and 150°C isothermal heat treatment are fiber extraction and fiber breakage, respectively, and both are AGM, while that of 210°C is debonding and delamination, which is DGM.