Functionalized Al2O3 fillers/glass fibers cloth/PTFE composites with excellent thermal properties

The alumina/glass fibers cloth/polytetrafluoroethylene composites were prepared by blending impregnation followed by hot compression method, and the dielectric, thermal, and mechanical properties of the composites with various Al2O3 contents (15–40 wt%) were investigated. The results show that the thermal conductivity and dielectric constant of the composites increase gradually, while the coefficient of thermal expansion decreases, with the Al2O3 content increasing. Composite substrates with 40 wt% Al2O3 exhibited ideal performance, which have reliable dielectric constant (er = 3.49), admissible dielectric loss (tanδ = 0.0027), low water absorption (0.04 %), low CTE of 8.73, 10.14 and 110.39 ppm/°C (X-, Y-, Z-direction, respectively), relatively high thermal conductivity (0.61 W m−1 K−1), and satisfactory flexural strength (66.1 MPa). Such compositions may be a promising material in high-frequency microwave substrates.