Preparing And Properties Of High Thermal Conductivity PA6/Graphite Composites

With the development of electron industry and high technology integrated circuit, requirement of thermal diffusivity of products is increasing. While the difficulty of metal molding and the poor anti-corrosion property limit its using. Plastics have excellent comprehensive performances, such as processing easily and cheap price, in which many areas can replace metal, but most plastics are the heat insulator, which largely limit their application in some field, so endowing plastics with the thermal performance can promote their practical value. In this paper, we choose graphite as the major thermally conductive filler, PA6 as the matrix resin, and filled thermally conductive filler to the matrix resin in order to prepare the thermal PA6 composites by melt blending. The main contents are as follows.The PA6/graphite composites with low and middle thermally conductive property through melt compounding was prepared. Three different types of coupling regents were applied to graphite’s surface treatment. The performance of PA6/graphite composites, in which the graphite was treated, was higher than that of PA6/graphite composites, in which the graphite was not treated. And the effect was outstanding when the amount of KH560 was 0.5% of the amount of graphite. With the increasing amount of graphite, the heat conductivity coefficient of the composites was increased obviously, the volume resistivity was reduced, meanwhile, the tensile strength, flexural strength and flexural modulus were increased, while the impact strength changed a little. When the amount of 325 mesh flake graphite was 50%, the composites’ heat conductivity coefficient was 2.35 W/(m-K). When the 325 mesh flake graphite and 1000 mesh colloidal graphite were mixed up at a ratio of 3:2, the fill effect was better than filling with a single graphite, and the good comprehensive properties were gained.The use of graphite improved the crystallization temperature of PA6, reduced the degree of crystallinity, and had little impact on the melting point. Non-isothermal crystallization kinetics study shows:the crystallization process of PA6 and PA6/graphite composites was divided into three-dimensional growth at the beginning and the 3-D growth at late stage. The crystallization half time is reduced with increasing of the cooling rate, Mo equation proved that crystallization activation energy first decreases and then increases with increasing graphite content. The addition of elastomer can improve the composites’ impact strength, while the tensile strength, flexural strength and flexural modulus were decreased, in which the effect of POE-g-MAH was more pronounced. The results showed that elastomer does not much affect the heating property and the volume resistivity, but will reduce its mobility.The composites PA6/graphite with high thermal conductivity was prepared. Three different types of lubricants were used cooperatively with paraffin and stearic acid to abtain the high thermal conductivity composites. The results showed that the heat conductivity coefficient of the material had been improved magnificently, while the mechanical property was decreased substantially. When the amount of 1000 mesh colloidal graphite was 85%, the heat conductivity coefficient was as high as 4.61 W/(m·K), and the volume resistivity was 1.01 X 106Ω·m, which had achieved the antistatic effect, however, the tensile strength decreased to 23.34 MPa. The addition of carbon fiber did not much affect the thermal conductivity and volume resistivity of composites but did good to the improvement of mechanical properties of the composites. When the content of 1000 mesh colloidal graphite was 70% and the amount of carbon fibers 12%, the heat conductivity of the composite was 4.37W/(mK), and the tensile strength can be obtained as high as 62.3 MPa.