Research On Heat-resistant Modification Of Injection Molded UHMWPE

Ultra-high molecular weight polyethylene（UHMWPE）is a thermoplastic material with extremely high molecular weight,characterized by high wear resistance,corrosion resistance,low temperature machinery,medical equipment and other fields.However,UHMWPE has high viscosity and is difficult to process by molding.Its poor heat resistance alresistance,impact resistance,as well as excellent biological compatibility,non-absorbency,and self-lubrication.UHMWPE products prepared by injection molding are widely used in textile industry,food packaging machinery,chemicalso limits its application in high temperature environments.Therefore,improving the heat resistance of UHMWPE is currently one of the important research topics.Previous studies on UHMWPE heat resistance modification were mostly based on compression molding and extrusion molding.Compared to compression molding and extrusion molding,UHMWPE injection molding has obvious differences in terms of products,molding principles,processing characteristics,and melting modes.In the injection molding process,UHMWPE materials are injected into the mold in the form of"jet stream"particles from the nozzle,and then the molten particles inside the mold melt together,resulting in dense and smooth products,due to its unique"jet flow"phenomenon,different material systems will affect the viscoelastic and microscopic morphology of the"jet flow"particles and further affect the performance of the product.In this study,cross-linking agents,inorganic fillers,and organic fillers were used to improve the heat resistance of UHMWPE through injection molding,while maintaining its excellent properties such as wear resistance and toughness,expanding its application range.The main work and conclusions of this paper are as follows:（1）The study investigated the effects of different crosslinking agents（DCP,DBPH）and their contents on the gelation rate,heat resistance,mechanical properties,and wear resistance of UHMWPE.The microstructure changes were observed through SEM,polarizing microscopy,and DSC testing.The results showed that a small amount of crosslinking agents can effectively improve the heat resistance and mechanical properties of UHMWPE.Among them,DCP had better modification effect.When the DCP content was 0.01%,the heat deformation temperature of UHMWPE reached a maximum of 99.1℃,with an increase of 22.3%,and the wear resistance basically remained unchanged.（2）Two inorganic fillers（Mo S₂and glass microbeads）and their contents were studied for their effects on the heat resistance,mechanical properties,and wear resistance of UHMWPE.The results showed that Mo S₂can improve the heat resistance and mechanical properties of UHMWPE.When the Mo S₂content was 5%,the heat deformation temperature of UHMWPE/Mo S₂composite material was 97.9℃,with an increase of 20.8%.However,its toughness decreased and the wear resistance also decreased significantly.A certain amount of glass microbeads can also improve the heat resistance and mechanical properties of UHMWPE,but the modification effect is worse than that of Mo S₂.（3）The effects of organic filler PTFE on the heat resistance,mechanical properties,and wear resistance of UHMWPE were studied.The results showed that PTFE can greatly improve the heat resistance of UHMWPE.When the PTFE content was 15%,the heat deformation temperature of UHMWPE/PTFE composite material reached a maximum of 104℃,with an increase of 28.4%.However,the mechanical properties and wear resistance decreased.Afterwards,keeping the PTFE content at 15%,the effects of different compatibilizers（maleic anhydride-grafted polyethylene and titanium ester coupling agent）on the mechanical and thermal properties of UHMWPE/PTFE composite material were studied,and it was found that the mechanical and thermal properties of UHMWPE/PTFE composite material became worse after adding different compatibilizers.（4）Using the fillers（DCP,PTFE,Mo S₂）with better modification effects from the above research results,further study was conducted on the effects of modification on the heat resistance and mechanical properties of UHMWPE.The results showed that the modification effect of PTFE/DCP on UHMWPE was relatively better.Compared with pure UHMWPE,its heat resistance and mechanical properties were improved.However,compared with adding a single filler,its heat resistance and mechanical properties were worse.