Studies On Microstucture Control And The Relationship Between Stucture And Performance Of Pu Based Materials

As thermoplastic elastomer, polyurethane material is widely used in tire and rubber roller, considering its outstanding wear resistance, perfect wide-rage physical property and lower rolling resistance. In this application, polyurethane elastomers are frequently using at high-speed and under high-load. The buildup of heat can lead to melting, tearing, or debonding. So the problem of polyurethane rubber is to improve the service life of polyurethane elastomers in a dynamic environment. To meet the requirements of tire for polyurethane material, we have used different polyol, isocyanate, chain extender and heat treatment to regulate and control the microstructure of polyurethane material, then research the effect of microstructure on the dynamic performance. What’s more, we characterize structure and properties through FTIR, SAXS, XRD, GPC, DSC, TG and DMTA. Here comes the specific work:(1) Three kinds of polyurethane material have been synthesized via a two-step method using HDI (Hexamethylene diisocyanate) as hard segment, polycaprolactone, polycarbonates and polyether as soft segments, respectively. Then researches about the effect of the compatibility and interaction between soft and hard segment on micro-phase separation, crystallization of hard segment and dynamic mechanical properties have been made. (2) Another three polyurethane materials also have been prepared, with polycarbonate as soft segment; HDI, PPDI (benzene diisocyanate), MDI (4,4’-diphenyl methylene diisocyanate) as hard segments by two-step method. Through the analysis of the symmetry and rigidity of hard segment, we discuss the influence of this properties on the micro-phase separation, crystallization of hard segment and the dynamic mechanical properties. (3) Different chain extenders HQEE(hydroquinone bis(2-hydroxy ethyl) ether), LBEF(biphenyl-4,4’-diol) and BDO(1,4-butanediol) have been used to prepare HDI-PC based polyurethane materials. And we also discuss the influence of chain extender on the micro-phase separation, crystallization of hard segment and the dynamic mechanical properties. (4) The impact of different heat treatment temperatures on the microstructure and the dynamic mechanical properties are studied in the last.The results shows that:the micro-phase separation and crystallization ability of hard segment in polyurethane materials could be regulated by the compatibility between soft segment and hard segment, the symmetry and flexibility of hard segment and the structure of the chain extender. The multi-level structure of polyurethane material and the crystallinity of hard segment have an important impact on the dynamic losses under low temperature and thermodynamic stability at high temperature. Meanwhile, the heat treatment of polyurethane material can improve the crystallization behavior of the hard segment, so as to achieve the purpose that the modulus and thermodynamic stability at high temperature of material could be enhanced.