The Preparation And Thermal Conductivity Propefrty Of Ultra High Molecular Weight Polyethylene Composites

Polymer materials are used in various applications due to their light weight, low cost.However, a majority of polymer matrices with thermal insulation materials restricts their wide use in applications such as thermal interface material and heat spreaders in microelectronic devices. Therefore, efforts to develop polymers possessing high thermal conductivity have attracted increasing attention. The most common way to improve the thermal conductivity of polymers is to add heat conducting particles in the polymer matrix which can form the thermally conductive networks to help phonon transmission. However, the interfacial interaction between the conducting particles and the polymer matrix introduces a continuous interfacial thermal resistance, which is disadvantage for improving the thermal conductivity of the polymer. Recent researches indicated that the geometric morphology and dispersion of filler within the polymer matrix have a significant effect on the interfacial structure.Additionally, the synergistic effects of hybrid filler and segregated structure formed in the polymer matrix are useful in reducing in interfacial thermal resistance. For this purpose, we study the effects of different conductive fillers with various morphology, hybrid thermal conductive particles, and the compression molding techniques on thermal conductive composites and thermal stability of UHMWPE. The details are as follows:The thermal conductivity of BN sheet?BN?/ultra-high-molecular-weight polyethylene?UHMWPE?, AIN particles?AlN?/UHMWPE and ?BN+MWCNT?/UHMWPE hybrid filler composites with segregated structures was investigated using a powder mixture and hot-pressing process. The thermal conductivity test show that the thermal conductivity of the composites increases with increasing filler content. When the filler content is 50wt%, the thermal. conductivity of ?BN+MWCNT?/UHMWPE>BN/UHMWPE>AlN/UHMWPE.Compared with the single filler BN/UHMWPE, ?BN+MWCNT?/UHMWPE composite's thermal conductivity is 1.505Wm^-1K^-1, increased by 64%.BN sheet and MWCNT entangled together, forming a compact thermal conduction networks, the synergistic effect between the two is helpful to improve the thermal conductivity of UHMWPE. Scanning electron microscopy ?SEM?, optical microscope ?OM?, atom force microscope ?AFM? shows that the networks of thermally conductive fillers and the interfacial thermal resistance at the filler boundaries played a major role in thermal conductivity of the segregated composites. TGA showed that the effect of BN+MWCNT on the thermal stability of the composites was not obvious, which is due to the formation of the thermal conductivity paths in the matrix and the inner energy can be quickly dissipated.In addition, the microstructure and thermal conductivity of BN/UHMWPE and?BN+MWCNT?/UHMWPE composite prepared by different temperature and pressure molding process were studied. The dispersion of filler under different compression molding was observed by optical microscopy and scanning electron microscopy. The results showed that integrated thermal conductive networks were formed after cold-pressing sintering. However,these networks would be destroyed by high pressure/high temperature treatment, and the thermal conductivity of composite decreased. The 1D-MWCNT is entangle with 2D-BNs and formed MWCNT-BN networks even at high pressure high temperature, leading to a nearly constant thermal conductivity(1.761Wm^-1K^-1 with addition of 50wt%?BN+MWCNT?). Besides,the dispersion of the fillers has a great influence on thermal stability of the composites.