Preparation And Friction Mechanism Of Self-lubricating Microcapsule/polyurethane Composite

Thermoplastic polyurethane elastomer(TPU)has excellent tear strength,superior elasticity,wide application temperature and excellent solvent resistance.It is widely used in synthetic leather,tires,light textiles,construction,machinery,medical treatment,automotive industry and military field.However,under the external alternating stress,some strong polar groups in TPU will quickly accumulate heat,which will cause thermal damage to the material;at the same time,the hard and soft segments in the TPU molecular structure are connected to each other,and the structural difference makes them different.The ability of some to withstand pressure is different.These problems result in the friction coefficient of TPU being higher than that of polyvinyl chloride and polytetrafluoroethylene,thus limiting its application in high friction fields.In this study,the sol-gel method and the interfacial polymerization process were used to successfully synthesize the self-lubricating microcapsules with liquid paraffin as the core material and polyurethane(PU)/silica(Si O₂)as the hybrid wall material,and the optimal synthesis was determined.The environment is alkaline.The prepared self-lubricating microcapsules are intact spherical,with a smooth outer surface,regular structure,and an average particle size of 540 nm.The thickness of the hybrid shell is about 100 nm,and the maximum initial decomposition temperature is 301.8?.Furthermore,self-lubricating microcapsules are used as the filling matrix,and they are compounded with the TPU material by in-situ polymerization to improve the self-lubricating properties of the TPU material.The self-lubricating properties of TPU materials containing different amounts of self-lubricating microcapsules have been characterized by a plastic sliding friction and wear tester.The existence of spherical microcapsules can effectively reduce the friction coefficient and abrasion of TPU materials.When the content of self-lubricating microcapsules is 1.2wt%,the average friction coefficient of the self-lubricating TPU composite is the lowest 0.301.Compared with pure TPU material,the friction coefficient and wear amount are reduced by 64.8%and 66.7%.At the same time,the thermal decomposition temperature,tensile strength and elongation at break of the self-lubricating TPU composite material increased by 4.6%,69.1%and 30.8%respectively,showing better thermal stability and mechanical properties,and extending the TPU material in special Service life in the field.Finally,the friction and wear mechanism of self-lubricating polyurethane composites was analyzed by scanning electron microscope.It has been confirmed that due to the flexible structure of the microcapsule hybrid shell and the release of the core material,the friction and wear mechanism of the self-lubricating TPU composite has changed from severe fatigue wear and adhesive wear to slight adhesive wear.