Improving thermal properties of ultrafine-glass-fiber reinforced PTFE hybrid composite via surface modification by (3-aminopropyl)triethoxysilane

Hybrid Polytetrafluoroethylene / ultrafine-glass-fiber (PTFE/UGF) composites were fabricated via a cold pressing and sintering method. The UGF were modified with coupling agent (3-aminopropyl) triethoxysilane (APTES) with different concentrations of 0%, 5%, 10% and 15%, respectively. Various thermal properties, including thermal conductivity, crystallization behavior, thermal decomposition temperature, coefficient of thermal expansion, high-temperature compressive creep behavior were investigated based on the composite morphology. Due to the substantially different properties between the inorganic particles and polymer matrix, the thermal conductivity and the thermal resistance index were increased, while the thermal expansion coefficient and high-temperature compressive creep strain of composites were decreased upon the addition of the UGF. Meanwhile, the thermal properties of the composites filled with surface treated ultrafine-fibers were significantly improved compared to the untreated composites. The thermal conductivity and thermal resistance index of PTFE hybrid composite with 15 wt% t-UGF content increased by 67.46% and 2.17% respectively, and the thermal expansion coefficient and high-temperature compressive creep strain decreased by 85.03% and 89.64% respectively in comparison with neat PTFE. These improvements were attributed to the surface treatment which could effectively enhance the interfacial compatibility between the UGF and the PTFE matrix, reducing the internal defects and improving the crystallinity in the composites.