Preparation And Properties Of Filled Thermal Conductive Polyamide6-Based Composites

Nowadays electronical devices become more and more thiner, lighter andversatile, which requires the thermal conductive materials to have good overallperformances. The resin-based thermal conductive composites attract lots ofattentions in the field of heat dissipation because of their excellent properties, such aslight weight, good chemical resistance, easy processing and excellent mechanicalproperties. In this paper, polyamide6（PA6） thermal conductive composites filledwith different kinds of fillers were manufactured by means of melt mixing, andthermal conductivity, electrical property, mechanical properties, heat deflectiontemperature （HDT） and melt flow index （MFI） of the composites were investigated.Al₂O₃, AlN and BN were added to the PA6respectively to prepare insulatingthermal conductive composites. The results showed that thermal conductivity of thecomposites increased with increasing the filler content. At the same filler fraction,thermal conductivity and HDT of BN/PA6composites were the highest among threekinds of composites, but its mechanical property was the worst. Compared with theother two composites, AlN/PA6composites had the best mechanical property andprocessability. Thermal conductivity of the Al₂O₃/PA6composites was1.06W·m-1·K-1when the Al₂O₃weight fraction was60%. These three kinds of thermalconductive composites all retained excellent electrical insulation.In order to obtain high thermal conductivity, flake graphite was used as highthermally conductive fillers to manufacture PA6thermal conductive composites. Itshowed that thermal conductivity and HDT of the composites increased with theincrease of graphite content, while surface resistivity, volume resistivity and MFIdecreased with increasing the graphite content, and changes of the surface resistivityand volume resistivity presented percolation phenomenon. Moreover, mechanicalproperty of the composites decreased distinctly after filling the flake graphite. Whenfibers were introduced into the composites, mechanical property and HDT of thecomposites improved significantly, in addition, particles and fibers hybrids werebenefit for forming thermal conductive networks.Flame retardants were added to the PA6thermal conductive composites toimprove flame retardance of the composites, which could make the thermalconductive composites suitable for practical applications. The results showed that redphosphor had good effect on improving flame retardance of the composites that contained graphite. With increasing red phosphor content, flame retardance of thecomposites improved, thermal conductivity kept stable, but mechanical propertydecreased significantly. So at the base of keeping flame retardance of the composites,the less red phosphor used the better.