Polytetrafluoroethylene‐based composites with improved thermal properties and excellent mechanical, dielectric properties using the synergy of mesoporous silica and aramid fiber

Abstract The high coefficient of thermal expansion (CTE) and low thermal conductivity (TC) restrict the application of polytetrafluoroethylene (PTFE). Improving the CTE and TC of PTFE requires high filler content, which dramatically deteriorates the dielectric and mechanical properties. Here, we propose mesoporous silica (mSiO₂) and aramid fiber (AF) as a hybrid filler, utilizing the synergy of the hybrid filler to develop a low additive filler for fabricating PTFE‐based composites with excellent comprehensive performance. The hybrid filler has a close interfacial combination with PTFE, and the uniformly dispersed mSiO₂ in PTFE impedes the thermal expansion of PTFE. Meanwhile, the AF constrains the PTFE expansion and acts as the “bridge”, inducing the hybrid filler to construct filler pathways to transfer the thermal stresses in the composite. Thus, the composite (AF‐5) exhibits a low CTE (59 ppm/°C) at a filler loading of only 15 vol%. Benefiting from the creation of thermal conductive pathways by the hybrid filler, the TC of AF‐5 increases by 50.4% relative to pure PTFE. Moreover, AF‐5 maintains good tensile strength (σ_c, 23.64 MPa), low dielectric constant and loss (ε_r, 2.21; tan δ, 2.25 × 10⁻³; 30 GHz). This work presents a novel avenue for designing polymer‐based composites with excellent overall properties. Highlights The mSiO₂ and AF synergistically construct ideal connected filler pathways. Hybrid filler reduces PTFE's CTE to 59 ppm/°C with only 15 vol% addition. Composite's TC is increased due to the creation of thermal conductive pathways. Composite shows excellent CTE, TC, mechanical, and dielectric properties.