Processing Of UHMWPE/Vectra A950/PEEK Composite By Spark Plasma Sintering

High performance special engineering plastics are strategic materials and one of the frontier research directions in polymer field.Thermotropic liquid crystalline polymers(Vectra A950),Polyether ether ketone(PEEK)and ultrahigh molecular weight polyethylene(UHMWPE)are three kinds of high performance polymers which are widely studied.Both of them have shortcomings and complementarities,and can be combined to obtain excellent composite materials.However,due to difficulties in processing,there is no relevant report in the literature.Vectra A950 and PEEK have high modulus and strength,but low toughness.UHMWPE has high toughness,but low modulus and strength.Therefore,they have strong complementarity in properties.Vectra A950 has good fluidity and short processing time,but high melting point and easy thermal degradation.Conversely,UHMWPE has poor fluidity,low melting point and long processing time,but good stability.Usually,Vectra A950 can be processed by conventional screw extrusion and injection molding,while UHMWPE can be processed by non-conventional methods such as compression molding and ram extrusion.Therefore,it is necessary to explore new processing methods to compound the materials with great difference in properties and incompatible interfaces.Spark plasma sintering(SPS)is a new material preparation and processing technology.It has the characteristics of uniform heating,fast heating,low sintering temperature and short sintering time.Without powder pre-forming,metal and ceramic powders are loaded into dies made of graphite and other materials.Therefore,SPS technology is a potential molding method for UHMWPE/Vectra A950 and UHMWPE/PEEK composites.However,the application of SPS in the processing of polymer materials has not attracted enough attention,only a few references on the processing of polymer-derived ceramics by SPS have been reported.Here,the SPS processing technology of UHMWPE,Vectra A950 and PEEK by SPS was studied,and the effects of current,voltage,temperature,time and vacuum on the material processing were investigated.The preparation of Vectra A950/UHMWPE and PEEK/UHMWPE composites by SPS was explored.Scanning electron microscope observation displayed that the UHMWPE samples processed by SPS were compact,without obvious pores and fusion defects,and the crystal size was small.Thermal analysis showed that the sintering pressure had little effect on the crystallization of UHMWPE samples,while the sintering temperature increased,the melting point decreased by about 2 °C,and the crystallinity decreased significantly,which may be due to the destruction of the primary structure of the powder by sintering at high temperature.The results of X-ray diffraction and infrared analysis showed that the UHMWPE samples had better crystallization.Compared with the primary powder,the crystal size and crystallinity increased slightly,and the sintering did not lead to chain fracture and oxidation.The compression modulus of UHMWPE samples is 401 MPa,and the compression strength is 28 MPa when the compression strain is 10%,which is close to that of UHMWPE samples processed by other methods.The particle size difference between Vectra A950 and UHMWPE is too large,the composite uniformity of the two is poor,and the flowability of Vectra A950 is too high,which leads to the leakage in the processing process,so the mold needs to be redesigned.The difference of melting point between UHMWPE and PEEK is large,so the interface adhesion strength is weak and the SPS processing parameters should be optimized.Therefore,SPS can rapidly process UHMWPE,but compounding UHMWPE with Vectra A950 and PEEK still needs further exploration.