Effect Of Cross-linking Structure On Properties Of Polyurethane Elastomer

Polyurethane(PUE)is a kind of widely used material with excellent comprehensive properties,which is used in household products,national defense industry,medical and health care,sporting goods and other industries.These excellent properties of PUE are closely related to its physical crosslinking structure and chemical crosslinking structure.Therefore,in order to broaden the application field of PUE,it is of great significance to study the influence of crosslinking structure on PUE performance.In this thesis,the effects of physical crosslinking,chemical crosslinking and reinforcement on the properties of PUE were studied.It was found that:1.The influence of physical crosslinking on PUE performance(1)Under physical crosslinking,the crosslinking density of polyester PUE is higher than that of polyether PUE.Among several polyols studied,the mechanical properties and wear resistance of polyester PUE are better than those of polyether PUE,especially PCDL PUE.The elasticity and tensile permanent deformation of polyether PUE are obviously larger than those of polyester PUE.Ppp PUE has the worst dynamic performance.On the whole,among the polyols discussed in the experiment,PTMG PUE has excellent comprehensive performance.(2)Under physical cross-linking,when the proportion of PCL in soft segment increases,the cross-linking density of PUE increases,and then the strength of PUE increases,while its permanent deformation and elasticity decrease,glass transition temperature increases and dynamic performance decreases.(3)When all the crosslinking in PUE is physical crosslinking,with the increase of physical crosslinking density,the mechanical properties and wear resistance of PUE become better,the glass transition temperature increases,but the permanent deformation and elasticity decrease.2.Influence of chemical crosslinking on PUE performance(1)Only different triols are introduced,so that the different chemical crosslinking structures in PUE are only caused by the different triols added.The results show that when the relative molecular weight of polyether triols increases,the crosslinking density of PUE decreases,the mechanical properties become better,and its dynamic properties improve.(2)Only by introducing different ternary chain extenders,the different chemical crosslinking structures in PUE are only caused by different ternary chain extenders.The results show that the strength of PUE is the highest when TIPA is used as chain extender,while the elasticity of PUE is the best among the three PUEs when TEOA is used as chain extender.In the range discussed in the experiment,when TMP is used as chain extender,the measured PUE performance is between TIPA and TEOA.(3)Only changing the chain extension coefficient(F),the results show that the crosslinking density of PUE decreases gradually with the increase of chain extension coefficient in the range of chain extension coefficient discussed.Moreover,when the chain extension coefficient increases,the mechanical properties and dynamic properties of PUE become better and better.In the range of chain extension coefficient discussed in the experiment,the chain extension coefficient has little effect on the glass transition temperature of PUE.(4)Only by changing the types of isocyanates,the different chemical cross-linked structures in PUE are only caused by different isocyanates.The results show that PUE synthesized by MDI and TDI-80 has good mechanical properties.NDI PUE has the best heat resistance.However,the effect of isocyanate types on the glass transition temperature of PUE is not obvious.The order of dynamic properties of PUE prepared by four isocyanates is TODI > NDI > MDI > TDI-80.(5)By changing the ratio of triol to diol or the ratio of ternary chain extender to binary chain extender,it was found that with the increase of the proportion of 330 N in soft segment or TMP in chain extender,the crosslinking density of PUE gradually increased,the mechanical properties and dynamic properties decreased,the glass transition temperature increased and the heat resistance improved.(6)For the system with chemically crosslinked PUE,when the chemically crosslinked structure is too much,the mechanical properties and dynamic properties of PUE will decrease.In addition,when the chemical crosslinking structure increases,the glass transition temperature of PUE increases,and the heat resistance improves.3.Influence of reinforcement on properties of PU materials with different cross-linked structures.(1)In the range discussed in the experiment,when the amount of fumed silica increases,the cross-linking density and mechanical strength of PUE increase continuously,but when the amount of fumed silica exceeds a certain range,the cross-linking density and mechanical strength may decrease in some areas of the test piece.(2)In the range discussed in the experiment,when the content of aramid short fiber increases,the mechanical strength of PUE gradually increases,and the dynamic properties are improved.