Preparation and molecular regulation of two-component microporous polyurethane elastomers with low viscosity
Terminated isocyanate(—NCO)two-component microporous polyurethane with low viscosity(LVMPU)prepolymer was synthesized from isophorone diisocyanate(IPDI)and polytetramethylene ether glycol(PTMEG)by prepolymer method.Then,two-component LVMPU was obtained from curing reaction at high temperature(130℃)after static defoaming at room temperature in the mold using 1,4-butanediol(BDO)and trimethylolpropane(TMP)as chain extenders,and a small amount of water in the air as foaming agent.The effects of m(IPDI)∶m(PTMEG),m(TMP)∶m(BDO),and residual—NCO content on the properties of two-component LVMPU elastomer were further analyzed.The results showed that when the mass ratio of IPDI to PTMEG was less than 5∶6 and the—NCO content was less than 2.4%,two-component LVMPU elastomer without—NCO could be obtained.Under the conditions of 20 g prepolymer prepared with m(IPDI)∶m(PTMEG)=2∶3,2.57 g BDO,and—NCO content 1.4%,the prepared two-component LVMPU elastomer exhibited the best mechanical properties.With the increase of—NCO content,the surface of two-component LVMPU had no cell structure,while the cross-sectional cells increased gradually with most of circular closed-cell structures with large pore sizes.When the mass ratio of TMP to BDO increased gradually,open-cell structures dominated the surface of two-component LVMPU elastomer,and the circular open-cell structures in the cross-section increased gradually,with relatively uniform pore size distribution and reduced average pore size.
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