Development And Application Of HMDI-polyurethane Elastomer

As the most widely used materials in polymer, polyurethane is widely used in all walks of life, because of its adjustable performance and flexible formula. But there is still be some non-ideal results, for example,insufficient anti-yellowing properties of elastic expansion joints in railways and bridges, it is prone to yellowing with water, oxygen, light and other environment factors. So it will destroy the material appearance,and affect the performance of the product.By HMDI, PTMEG1000 and EP3600, we prepared a polyurethane material by semi-prepolymer method, which has good anti-yellowing,strength, and elongation. The different factors in the experimental formula, the different isocyanate-type materials, and the performance of the HMDI-PU coating was studied.(1) Through the study of formula that is based on HMDI,PTMEG1000, EP3600, and BDO, testing the effect of different experimental factors on the performance of materials, it showed that when the ratio of the polyether polyol PTMG1000 to EP3600 in the pre-polymer component was 4:6, the NCO content of the pre-polymer was 9.5%, the amount of the chain extender BDO was 2.7g, and the isocyanate index R value was 1.10, the HMDI-polyurethane has best properties, and the hardness of Shore A was 48, the tensile strength was 7.21 MPa and the elongation at break was 500%.(2) Without changing the other conditions in the experiment,different types of isocyanates were used as reaction materials. The experimental results showed that the mechanical strength of HMDI-PU was higher than other types, and the elongation at break was weaker than IPDI-PU. Both the contact angle test and the water absorption test showed that HMDI-PU was best, IPDI-PU was second, and TDI-PU was worst in water resistance. Moreover, the HMDI-PU had better heat resistance than other types.(3) Through experiments in enterprise, we succeeded in converting the previously resin formulation into a product of coating by adding other supporting auxiliaries. By comparison and analysis of experimental results, we found that, the HMDI-PU coating had a low hardness and a feeble tensile strength, but the elongation at break had increased, and the water resistance of the materials had definitely improved. Moreover, the degree of discoloration of the HMDI-PU coating was just between the non-discoloration and the slight discoloration after UV irradiation experiment, so the HMDI-PU coating had a better anti-yellowing performance. With the results of other performances,it showed that the performance of the HMDI-PU coating could meet the requirements.