Effect of fiber diameter on thermal properties of short-glass-fiber-reinforced PTFE-based composites

Polytetrafluoroethylene (PTFE) matrix has been reinforced by short glass fiber (SGF) with various diameters (8, 4 and 2 μm) in this experiment, and the effects of fiber diameter on the thermal properties of PTFE-based composites, including thermal resistance index ( T HRI ), thermal conductivity ( λ ), melting temperature ( T m ), coefficient of thermal expansion (CTEz) and high-temperature compression-creep, are investigated. The results show that the thermal properties could be improved with the amount of SGF. However, this could be due to the fact that the packings have been compelled by different compression forces caused by composite shrinkage during preparation, the interface between packing with large diameter and PTFE matrix is significantly different from that of the small one, resulting in the crystallinity ( X c ), and T HRI of PTFE-based composites decreases with the decreasing fiber diameter. Moreover, the small-diameter fiber is easier to debond from PTFE matrix due to the inferior physical stability of interface, the λ decreases with the decrease of the fiber diameter, while CTEz and creep strain value increases. From XRD analysis, the results of crystallite size revealed that the lamella thickness of composite decreases, which means that the T m of the PTFE-based composites has also decreased with the decreasing fiber diameter.