Research On The Relationship Between Heat-resistance And Structure Of Castable Polyurethane Elastomer

Polyurethane elastomer has excellent physical charactertistics such as high tensilestrength, high elasticity and high elongation,and it has excellent abrasion resistance, oilresistance,tear resistance and chemical resistance,except that,the polyurethane elastomer alsohas good damping performance and can change its hardness in wide adjustment. All of theseexcellentperformances make polyurethane elastomer have a wide range of applications. But,because of its big internal heat generation in danamic conditions and poor heat resistanceperformance, itsmechancial performances reduce significantily inhigh temperature conditons,whichmakes the strength, handness and modulus of the elastomer drop badly and the overallsize change, in high temperature conditons, and also limiting the application of polyurethaneelastomerindynamicand high temperature working conditions.In this paper, prpolyme method was usded in order to prepare castable polyurethaneelastomer with low endogenous heat and good heat resistancer, the effects of the nNCO/nOHstartingratio of prepolymers,the soft segments and nano SiO₂filler on dynamic performance,heatresistantand elsatomerstucture of the polyurethane elastomerwere investigatedin detail.Thestudy showed that:1) The increase of nNCO/nOHstarting ratio of prepolymers, improved the uniformity ofprepolymers, and promoted the formation of more perfect elastomer structure, which wasbeneficial to the orderly arrangement of the soft segments and hard segments, and form moreperfectmicrophase structure.2) The more perfect microphase structure was benefit to bring down internal heatgeneration, which can improve the heat resistance of the matertial on internal heat generationpart, and, to some ectent, also improve elastomers mechancial properties under normal andhigh temperature to raisethe elastomerheatresistance.3) The method of nano SiO₂filler modifying elastomer had significantly enhancedstrenghth and toughness, and improved heat resistance. The effect mechanisation of SiO₂enhancementwas found that the hydroxylgroups on thesurfaceof SiO₂, had reactedwith the–NCO groups of the polyurethane hard segments, which enhanced intermolecular forcesbetweenhardsegments, thusimproved strenghth,toughness and heat resistance. 4) As nano SiO₂had increased material mechanics performance, it had aslo incresasdinternal heat generation in dynamic conditions. But increasing of nNCO/nOHstarting ratio ofprepolymers, and modifying the elastomers with nano SiO₂, was found that could reduceinternalheat generation, at the same time improved the heatresistance.