The Study On Properties Of Insulting Thermal Conductive PA6 Composites

The development of insulating thermal conductive polymer composite materials is the important subject to solve the heat dissipation of electronical devices and LED lamps. Since mechanical properties or thermal conductivity of many insulating thermal conductive composites reported can not meet the demand of many strict situations, in this paper, PA6 was used as the matrix and Al2O3 was used as thermal conductive filler, the insulating thermal conductive composites were prepared by a twin-screw extrude machine. The effect of Al2O3 content and particle size on the properties of PA6/Al2O3 composites were studied. The results showed that the thermal conductivity of PA6/Al2O3 composites increased with the increasing of Al2O3 content, while the mechanical properties decreased. And the thermal conductivity of PA6/Al2O3 composites increased with the increasing of Al2O3 particles size, while the mechanical properties also decreased.. When Al2O3 content was 70 wt%, the thermal conductivity of 4μm、6μm、15μm and 40μm Al2O3/PA6 composites reached 1.213 W/(m K),1.268 W/(m K),1.289 W/(m K) and 1.455 W/(m K), respectively, while the tensile strength were just 57.37 MPa,53.77 MPa,52.12 MPa and 49.5 MPa, respectively.In order to improve the mechanical properties of PA6/Al2O3 composites, in this paper, a blocked isocyanate silane, which was prepared by methyl ethyl ketone oxime and isocyanate, was used as a coupling agent to modify the surface of Al2O3 particles. And the properties of blocked isocyanate silane modified PA6/Al2O3 composites were investigated. The SEM images showed that the blocked isocyanate silane can improve the dispersion of Al2O3 particles and enhance the interaction within PA6 matrix. Balance torque and mechanical properties results showed that the blocked isocyanate silane could deblock in the process of melting process and react in situ with amino and carboxyl groups of PA6 chains, which have a effect of chain extension, resulting in improving the mechanical properties of the PA6/Al2O3 composites. The thermal conductivity of blocked isocyanate silane modified PA6/Al2O3 composites was also increased compared to unmodified at the same loading of Al2O3. When Al2O3 content increased to 70 wt%, the tensile strength reached 85.16 MPa, showing significant enhancement compared with neat PA6. The thermal conductivity was 1.18 W/(m·K), higher than that of pure PA6 by 2.8 times.Considering the mechanical properties and the difficult of preparation,60 wt% filler loading was suit, but the thermal conductivity of composites were lower at that loading. In order to improve the thermal conductivity of composites, the mixture of different size Al2O3 were studied. The results showed that mixture of 6 microns and 40 microns Al2O3 with the mass ratio of 1:1 filled PA6 composites owned higher mechanical properties and thermal conductivity. Then the above optimum distribution of Al2O3 were mixed with high thermal conductive filler, AlN, BN and SiC, resprctively. the effect on high thermal conductivity filler type and content of high thermal conductivity filler on the properties of composites were studied.