Preparation And Research On Structure And Properties Of UHMWPE Composite

Ultra-high molecular weight polyethylene(UHMWPE)has excellent comprehensive properties,so it is widely used in many fields.Due to the extremely high molecular weight of UHMWPE,the dense entanglement of molecular chains during melt processing leads to extremely high melt viscosity.Therefore,it is difficult to use conventional extrusion and injection molding equipment for processing and molding,which greatly limits the efficiency and application scope of its mass production.In this paper,UHMWPE is used as the matrix material,and the polymer materials polylactic acid(PLA),polyolefin elastomer(POE)and metallocene polyethylene(m PE)with higher melt flow rate(MFR)are added respectively,and small lubricants polyethylene glycol(PEG)with lubricating effect.In order to reduce the degree of molecular entanglement,increase molecular chain mobility and improve processing performance.And further analysis from the flow behavior,microstructure and macroscopic properties,etc,provides an important reference for the preparation of UHMWPE composites with good processing properties.The main work and conclusions of this paper are as follows:1.Melt flow behavior and processing properties of UHMWPE compositesComposite materials with different addition ratios and blending forms are prepared,using UHMWPE as a matrix,adding PLA,PEG,POE,and m PE with high MFR and lubricating effect.The degree of molecular chain entanglement,apparent viscosity and extrudate state of the composite material were studied,and the processing and molding properties were analyzed.The results show that all four additive phases can improve the processing performance of the composite in different ways.PLA can destroy the entangled network of UHMWPE to enhance the melt flow capacity of UHMWPE;As a small molecule lubricant,PEG plays a role of micro-phase lubrication between UHMWPE molecular chains,and part of it migrates to the surface during extrusion molding to play a role in wall lubrication;POE has a high MFR,which greatly reduces the apparent viscosity and shear pressure of the UHMWPE/POE;The molecular chains of m PE and UHMWPE can be more closely entangled,resulting in a weaker improvement in the processing performance of UHMWPE/m PE.2.Microstructure and properties of UHMWPE compositesThe quenched section morphology,crystallinity and nanoindentation properties of four kinds of UHMWPE composites were studied,and the influence of the addition phase,addition ratio and blending form on the internal structure and properties of UHMWPE composites was analyzed.It is found that the hardness and modulus of the added phase,the ability to bond with the matrix and the influence of the relative crystallinity of the addition determine the hardness and modulus of the UHMWPE composite.Therefore,the properties of different composite materials have different trends with the proportion of added components.The increase of PLA content increases the crystallinity of the composite material first and then decreases.The higher hardness and modulus of PLA increase the hardness and modulus of the composite material.Small molecule PEG has less damage to the internal entanglement network of UHMWPE.With the increase of PEG content,its soft molecular chain effect makes the hardness and modulus of composite material decrease slightly.When the content of PEG is 3%,the degree of entanglement of the molecular chains of the composite material is small,so the highest degree of crystallinity is obtained.As the content of POE and m PE increases,the crystallinity of UHMWPE decreases.POE with a smaller modulus and hardness reduces the modulus and hardness of the composite material,while the modulus and hardness of UHMWPE/m PE first decrease and then increase.3.Macroscopic properties of UHMWPE composite materialsThrough the tensile,compression,impact tests and the fracture surface morphology,the mechanical properties of the four composite materials were studied with the added phase content,and through the water contact angle test,the surface wettability of the four composite materials was analyzed with the addition of the phase ratio.It is found that the bonding between the additive phase and the matrix has an important influence on the mechanical properties of the composite material,and the surface wettability is closely related to the polarity and surface roughness of the composite material.It can be seen from the section morphology that the presence of PLA in the UHMWPE matrix causes stress concentration.With the increase of PLA content,the composite material gradually changes from toughness to brittleness,the impact strength decreases greatly,and the water contact angle changes little.The small molecule lubricant PEG containing hydrophilic groups has little effect on the mechanical properties of UHMWPE.With the increase of PEG content,UHMWPE/PEG can maintain high toughness and impact strength,and the water contact angle is reduced.POE is uniformly dispersed in the UHMWPE matrix.As the content of POE increases,the toughness and impact strength of UHMWPE/POE decrease,while the hydrophobicity increases.m PE can be miscible with UHMWPE,so as the content of m PE increases,the composite material can still maintain high impact strength and toughness,but the increase in surface roughness increases the water contact angle of the material.