Studies On Preparation And Permormances Of Thermal Conductive PA6Composites

With the rapid development of social society and industry, the demanding for materials are increasing, further, the requirement of multi-functional and high performance materials are put forward. Recently, the research of thermal conductive composites with good heat dissipation performance is one of the hot spot. Companies such as DSM, polyone and Coolpolymer introduce their new thermal conductive composites from time to time. Alumina are generally used to make high thermal conductive and electrical insulation composites. For the thermal conductivity ratio of alumina (30Wm-1K-1) and polymer (0.2～0.3Wm-1K-1) are higher than100and it is with extensive resource and lower cost. However, we usually have to fill high concentration fillers to fabricate high thermal conductive materials, and this always increase the viscosity of the composites and lower the mechanical properties. This two issues are widely exist in the preparation of thermal conductive composites. Focused on the issues, we chose PA6as the matrix, Al2O3as the main filler, further adding some other high thermal conductive fillers to product an complementary effect with Al2O3to reduce the whole filler content as much as possible. Finally, a series of excellent comprehensive composites were gained. Our detailed research works are implemented follows:1. PA6and different Al2O3particles are mixed to prepare PA6/Al2O3composites by melt extruding methods, and their thermal, electrical and mechanical properties were researched. The thermal conductivity test results showed that composites with large alumina particle sizes (20～60μm) have better thermal performance than smaller alumina particle sizes (1～2μm) under the same filler loading. For example at the alumina content of70wt%, the through-plane thermal conductivity of the two single filler composites are1.24W/m-1k-1and1.09W/m-1k-1respectively. The SEM images of the two composites showed that alumina particles are uniformly dispersed in the PA6matrix and showed well adhesion with PA6matrix. The electrical testing results showed that all the PA6/Al2O3composites are insulation. The mechanical results showed that with the increasing content of alumina, the tensile modulus and strength and the flexural modulus and strength are increasing. When the Al2O3content is more than60wt%, the tensile and flexural strength are beginning to decrease, but the descender is less than10%under our testing range. 2. We chose BN, graphite and MWNT to mix with alumina and prepared three phrase composites respectively, and researched their thermal, electrical and mechanical properties also. The thermal conductivity results showed that in through-plane direction, natural graphite and MWNT have the same effect, but in in-plane direction, graphite has the best results. The testing results of electrical properties were as follows, the PA6/Al2O3/BN and PA6/Al2O3/graphite composites were insulative materials at the BN and graphite content of5wt%; However, at the MWNT content of3wt%, the electrical conductivity of PA6/AI2O3/MWNT could reached10-1S/m, it is a very high magnitude for polymer materials. The mechanical properties results showed that the three high thermal conductive filler made no great influence on the mechanical performance compared to the PA6/Al2O3composites.3. Al2O3, graphite and MWNT were incorporated into PA6matrix simultaneously and the thermal and electrical multiphase composites were investigated. The thermal conductivity test results improved that a variety of different dimensions of mixed fillers were helpful to the formation of thermal conductive networks. In our project, fixed the loading of Al2O3, graphite and MWNT at65,5,1.5wt%, the through-plane thermal conductivity of the multiphase composites could reach1.80Wm-k-1. Compared with the same content of PA6/Al2O3/graphite composite, the addition of1.5wt%MWNT can improve the electrical conductivity from10-10S/m to10-6S/m.