Studies On The Hydrolysis-aging Resistance Of Thermoplastic Polyurethane Elastomer

Thermoplastic polyurethane (TPU) elastomer has excellent mechanical properties, high abrasion resistance, anti-oil properties etc, which is widely used as a toughing material to improve toughness. However, polyester-based TPU is easily hydrolytic, which limits the application, and there's few reseach work about how to improve TPU's hydrolysis-aging resistance. In this paper, the effects of PCD, epoxy compounds (glycidyl phenyl ether (PGE), 3-(2, 3-Epoxypropoxy) propyltrimethoxy- silane (KH560) and epoxy (E51)), SEBS-g-MAH, inorganic filler (CaCO3, BaSO4) on the hydrolysis-aging resistance, mechanical properties, processing properties, thermo- stability of TPU are inverstigated.Firstly, the influence of PCD and SEBS-g-MAH on mechanical properties, hydrolysis-aging stablity and thermostabity of TPU were studied. The results showed: adding PCD to TPU, the maintenance of mechanical properties in 25℃air or 80℃water, tensile strength and elongation at break of TPU were increased, while water absorptivity in 25℃air or 80℃water and the melt flow index were decreased. When the content of PCD was 3%wt, the hydrolysis-aging resistance of TPU became the best. For the TPU/SEBS-MAH blends, as the amount of MAH-SEBS increased, the tensile strength, elongation at break and maintenance of mechanical properties in 25℃air or 80℃water were increased, while the melt flow index and water absorptivity in 25℃air or 80℃water were decreased. When the content of SEBS-MAH reached 15%wt, the hydrolysis-aging resistance of the TPU became the best. The FTIR analysis revealed that the characteristic groups of the PCD and SEBS-g-MAH have grafted on the TPU backbone chain, separately. The DSC analysis showed there were exisisting some compatibity between the TPU and PCD or SEBS-g-MAH and TPU. The TGA results indicated that the addition of PCD increased the thermo stablity of TPU while SEBS-g-MAH made it worse.Secondly, the effects of glycidyl phenyl ether (PGE), 3-(2, 3-Epoxypropoxy) propyltrimethoxysilane (KH560) and epoxy (E51) on the hydrolysis-aging resistance, mechanical properties, thermostabity of the TPU were investigated. The results showed: adding KH560 to TPU, the tensile strength, elongation at break, and the maintenance of mechanical properties in 25℃air or 80℃water were increased, while water absorptivity in 25℃air or 80℃water and the melt flow index of TPU were decreased. Adding PGE or E51 to TPU, the tensile strength, elongation at break, water absorptivity in 80℃water or in 25℃air and the melt flow index of TPU were decreased, while the maintenance of mechanical properties in 25℃air or 80℃water increased. The DSC analysis indicated that there was exsisting some compatibility between TPU and these there epoxy compounds. The FTIR analysis showed the characteristic groups of there epoxy compounds had grafted on the TPU backbone chain respectively, moreover there might be exsisting hydrogen bond between the epoxy compounds and TPU. The TGA analysis indicated that all of them decreased the thermo stability of TPU.Thirdly, the effects of BaSO₄, CaCO₃ on mechanical properties, hydrolysis -aging resistance and thermostabity of TPU were studied. The results revealed that adding BaSO₄ to TPU, the mechanical properties and maintenance of mechanical properties in 25℃air or 80℃water showed a trend from ascent to descent, while water absorptivity in 25℃air or 80℃water and melt flow index were decreased. Adding CaCO₃ to TPU, the mechanical properties were firstly increased then decreased, water absorptivity in 25℃air or 80℃water and melt flow index were decreased, maintenance of mechanical properties in 25℃air or 80℃water were increased. When the content of CaCO₃ achieved 20%wt, the hydrolysis-aging resistance got the best effect, while the mechanical properties were decreased compared with pure TPU. The TGA results indicated that adding BaSO₄ or CaCO₃ both decreased the thermo-stability of TPU.Fourthly, the effects of different hydrolysis resistance agents on the balance torque of TPU were investigated. The results showed that the processing properties of TPU were decreased by PCD while improved in the presence of SEBS-g-MAH, epoxy compouds and inorganical filler.