Synthesis And Properties Of Low-Temperature Resistant Thermoplastic Polyurethane Elastomer

Thermoplastic polyurethane elastomer(TPU)is a kind of polymer synthetic material between plastic and rubber.It not only has a high elasticity of rubber and high strength of plastic,but also has unique melting and soluble properties.Therefore,it is widely used in aerospace,medical equipment,shipbuilding and automobile industry,decoration materials,and other defense military and national economic fields.However,TPU tends to lose the high elasticity of the elastomer itself in low temperature environments,and the problem of embrittlement occurs,which limits its application in low temperature environments.Therefore,in this paper,the factors affecting the lowtemperature resistance of TPU were explored,and on this basis,the physical and chemical modification of TPU were carried out respectively to synthesize TPU with excellent low-temperature resistance and good mechanical properties.The main contents and results are as follows:(1)In order to explore the factors affecting the low-temperature resistance of TPU,this paper investigated the types and molecular weights of polymer diols,the types of diisocyanates,chain extension coefficient,hard segment content,and other factors.The soft segment structure has the greatest impact on the low temperature resistance of TPU,and the hard segment structure has the greatest impact on the mechanical properties of TPU.When polytetrahydrofuran ether glycol(PTMG),4,4'-dicyclohexyl methane diisocyanate(HMDI),and 1,4-butanediol(BDO)were used as raw materials,the chain extension coefficient was 1.00,and the hard segment content was 15%,the glass transition temperature(Tg)of when the chain extension coefficient is 1.00 and the hard segment content is 15%.(2)In order to systematically explore the effect of physical modification on the low-temperature resistance of TPU,inorganic fillers and organic fillers were mixed with TPU respectively by solution blending method in this paper.The influence law and mechanism of fillers on TPU were explored,and the problems of easy agglomeration and difficult dispersion of fillers in TPU were solved.The study found that the addition of filler makes the Tg change of the soft segment of TPU not obvious,but it has a greater impact on the Tg of the hard segment.Inorganic fillers can significantly improve the mechanical properties of TPU,especially nano-CaCO3 modified TPU,whose tensile strength is 36.8%higher than that of unmodified TPU,while Tg remains unchanged.(3)In order to explore the effect of chemical modification on the low-temperature resistance of TPU,the chemical structure of TPU was modified from the perspective of the chain extender.Three novel TPUs were synthesized by imidazoline(IM),piperazine(PPA)and 2-methylpiperazine(2-PPA)as chain extenders.The high elasticity of TPU was maintained at a very low temperature,and good mechanical properties were taken into account at room temperature.Among them,the Tg of TPU synthesized with IM as a chain extender can be as low as-103.9 ?,and the tensile strength is 12.97 times that of TPU synthesized with alcohol chain extenders,which well solves the contradiction between low-temperature resistance and mechanical properties of TPU.The new TPU not only maintains good high elasticity at low temperatures,but also has excellent mechanical properties,providing a new technical approach for the application of TPU in extremely low-temperature environments.