热压成型温度对PTFE/SiO_2复合材料性能的影响

Influences of thermoforming temperature on the properties of PTFE/SiO_2 composites

采用热压工艺制备了PTFE/SiO2微波复合基板材料,研究了热压温度对PTFE/SiO2复合材料的性能及显微结构的影响。差示扫描量热法分析表明PTFE结晶度随热压成型温度上升而升高,熔限先变宽后变窄。同时通过扫描电镜观察发现,热压成型温度升高使复合材料表面出现气孔,材料内部气孔数目增多,从而导致材料密度、相对介电常数下降,吸水率A升高。由于PTFE树脂结晶度与材料显微结构共同作用,介电损耗先降低后增高,热导率Kc则先增高后降低。热压温度为370℃时,复合材料性能较好(εr=2.90,tanδ=0.001 1,A=0.58‰,Kc=0.566W/(m·℃))。

PTFE/SiO2 composite materials were prepared by thermoforming process under a certain pressure. The influences of thermoforming temperature on the microstructure and properties of PTFE/SiO2 composites were investigated. Differential scanning calorimetry analysis indicates that the degree of polymerization of PTFE decreases and crystallinity increases with an increase of thermoforming temperature. The melting range is broadened then get narrowed as the temperature increases. Pores are observed in samples by scanning electron microscope and porosity is raised by increasing temperature, which lead to the decrease of density and relative permittivity, and the increase of water absorption. The dielectric loss is decreased and then increased as the temperature increases due to the influences of crystallinity and microstructure of composites. On the other hand, the thermal conductivity increases and then decreases. When the thermoforming temperature is 370 ℃, the composite material possesses good performance （ετ=2.90, tanδ=0.00l 1, A=0.58‰, Kc=0.566 W/（m · ℃））.