Research On Rheological Behavior And Mechanical Properties Of UHMWPE And Its Composites

UHMWPE is a high-performance specialty polymer.The extremely long molecular chain increases the number of entanglements between the chain itself and the chain,resulting in a very large melt viscosity,which is difficult to process and produce by melt flow processing.At present,there are generally three ways to improve the processing properties of UHMWPE:by controlling the catalytic synthesis process,low-entanglement UHMWPE can be prepared,but the process is very complicated and expensive;by adding a certain amount of processing aids or low molecular weight polymers,UHMWPE can be improved to a certain extent.However,it will significantly reduce the mechanical and other properties of UHMWPE;by improving the processing equipment,melting defects cannot be avoided,and a large amount of processing aids are also required,which will also affect the environment.In this paper,the modification of UHMWPE by combining low molecular weight polymers and nanoparticles aims to improve the processing properties while enhancing the mechanical properties and expand the application of UHMWPE.（1）This topic first studies five UHMWPE raw materials and their molded products,explores the relationship between the particle size,molecular weight,entanglement and other factors of raw materials and product properties,using differential scanning calorimetry（DSC）,dynamic thermomechanical analysis（DMA）,Raman spectroscopy,etc.analyzed its phase composition and structure,and found that GUR400Fine has excellent mechanical properties and excellent processing properties.（2）In order to reduce the viscosity of UHMWPE,GUR400Fine was melt-blended with different contents of HDPE2200J with excellent fluidity,and the effect of HDPE content on the rheological behavior of the blend was studied by DMA and capillary rheometer.The mechanical properties and erosion properties were tested and analyzed,and it was found that the content ratio of 50/50 had the best comprehensive properties.（3）In order to further reduce the viscosity of the blends,UHMWPE/HDPE/Ti O₂composites with different particle sizes and contents were prepared by dissolving dispersion-melt blending,and the mechanism of disentanglement and viscosity reduction of polymers by nanoparticles was analyzed.Under the shear rate,the slip ability of the molecular chain increases and the viscosity of the matrix decreases further under the influence of Ti O₂.At the same time,the tensile properties and erosion properties of UHMWPE/HDPE/Ti O₂ composites are significantly improved.By combining low molecular weight polymers and nanoparticles to reduce the viscosity of UHMWPE,and at the same time to strengthen the mechanical properties,a composite material with processable viscosity and excellent performance was successfully prepared,which provides a new research for improving the processability of UHMWPE ideas.