Abstract: Two-component polyurethane （PU） sealants with an inorganic CaCO3 filler were developed to improve the performance for use as a high-speed railway sealing sealant. The surface morphology of polyurethane sealants with different contents of the CaCO3 filler was observed using a scanning electron microscope. The mechanical and adhesion properties of the PU sealant samples were analyzed and their heat and water resistance were evaluated. The results indicated that the inorganic filler could reduce the surface flatness of the sealants but improved their roughness. The appropriate addition amount of the CaCO3 filler enhanced the tensile strength， elongation at break， and modulus of the sealants； however， the excessive amount of the filler reduced their elongation at break. With the addition of the filler， the adhesion， heat resistance， and water resistance of the sealants were all improved considerably. In addition， the addition amount of 30 wt% CaCO3 filler was recommended for the PU sealants to achieved optimal comprehensive performances. The findings in this study provide a reference for enhancing the cost-effectiveness and performance of PU-based high-speed railway sealing sealants.

Key words: high-speed railway, polyurethane sealant, performance evaluation, heat resistance, micro-morphology