Design of Novel POB/h-BN Co-Filled PTFE Composites with Enhanced Thermal–Mechanical Properties

Abstract

Polytetrafluoroethylene (PTFE) is provided with excellent self-lubricating properties and corrosion resistance. However, the lower thermal resistance greatly limits its high-temperature applications. In the present work, two types of fillers with rigid organic polymers and submicron-sized inorganic hexagonal boron nitride (h-BN) were added to the PTFE matrix. The microstructure and thermal–mechanical properties of PTFE-based composites with different filler types or ratios were comparatively investigated. The results suggested that the polyphenyl ester (POB)/h-BN co-filled PTFE composites exhibited excellent thermal–mechanical properties compared with the polyimide (PI)/h-BN/PTFE materials at high temperature. The optimal ratios of POB and h-BN were 25 wt.% and 5 wt.%, respectively. The Vicat softening temperature of 25 wt.% POB/5 wt.% PI/PTFE composite increased by 41.3% compared to that of pure PTFE, which was due to the cross-linked reticulation structure with regularly distributed pores and higher crystallization degree. The storage modulus increased from 51.99 MPa to 685.76 MPa at 260 °C and reached 187.82 MPa at 320 °C. The uniform distribution of anisotropic orientation of the h-BN flakes showed an obvious pinning effect, and further improved the thermal–mechanical stability of POB/h-BN/PTFE composites.

Keywords

• polytetrafluoroethylene
• microstructure
• thermal resistance
• h-BN flakes
• dynamic thermomechanical analysis