Study On Preparation And Performance Of Two-component Polyurethane Sealant

In recent years, the high-speed railway of our country develops fast, the slabballastless track occupy a large proportion of China`s high-speed rail track. Thecantilever bumping abutment between two track boards needs caulk compound.The frequently-used silicone sealant and polysulfide sealant have low intensity,poor adhesion and deformation. Although the strength and adhesive performanceof the polyurethane sealant are good, enduring high-low temperature and wet-heataging are poor. So the paper will develop a lowcost two-component polyurethanesealant, mainly to solve the problem of enduring high-low temperature andwet-heat aging.The paper selects MDI-100LL modified by the carbodiimide as the hardsegment, the hydrolysis resistance performance is excellent, preferably flexiblepolyether polyols PTMEG as a soft segment, small molecule alcohol BDO withmoderate activity as chain extenders. We adopt prepolymer method to synthesizethe two-component polyurethane sealant. Two n-butyl amine titration method isadopted to measure the content of NCO, we determine the optimum reactiontemperature of synthesis is80℃, optimum reaction time is2h. After determiningthe synthetic process, we research n-NCO/n-OH value （R value） affect theperformance of polyurethane sealant, including the mechanical properties, thermalstability and water absorption. The results showed that when the R value is1.15,the mechanical properties of polyurethane sealant is best, the viscosity is5865mPa.s, the tensile strength is18.97MPa, the elongation at break is436.85%, theadhesive strength is7.96MPa, water absorption is1.79%, the thermallydecomposable performance is relatively stable. Based on the best R value, weresearch the influence of polyurethane sealant with complex of different molecularweight PTMEG. The results found that when PTMEG2000/PTMEG1000is1:1,the integrated performance of polyurethane sealant is best, the tensile strength is17.07MPa, the elongation at break is502.23%, the adhesive strength is8.53MPa.Based on the above tests, in order to reduce costs as well as to increase themechanical properties of the sealant, a kind of light CaCO3filler and carbon blackwere added into the system. The results showed that when the content of CaCO3is30%, the filler uniformly dispersed in the polyurethane system, the mechanicalproperties is best, the tensile strength is20.07MPa, the elongation at break is412.19%, the adhesive strength is9.43MPa, the water absorption is1.99%, the residual mass of600℃is8.22%and the thermal decomposition is stable.Compared with the filler of CaCO3,5%,10%,15%and20%carbon black particleswere added, the results showed that when the content of carbon black is10%, thefiller uniformly dispersed in the polyurethane system, the mechanical performanceis best, the tensile strength is21.76MPa, the elongation at break is411.32%, theadhesive strength is9.76MPa, water absorption is1.99%,600℃residual mass is8.22%and the thermal decomposition is stable.The optimum formulation of the three samples of pure PU,30%CaCO3/PU,10%carbon black/PU were selected for high-low temperature and damp-heat test.Before and after the high-low temperature and damp-heat test, we found that10%carbon black/PU has the lowest rate of aging, followed by30%CaCO3/PU and thepure PU material has the highest rate of aging.