A study on the properties and working mechanism of a waterborne polyurethane-modified silicate-based coating

Herein, the effects of the amount of waterborne polyurethane, silica sol and fillers on the compressive and bending strength, temperature resistance and acid resistance of waterborne polyurethane-modified silicate-based coatings were investigated. The results indicated that the modified coating showed higher mechanical properties, impermeability and bonding properties when the amounts of polyurethane and silica sol were 10% and 4%, respectively. The room temperature strength, temperature resistance and acid resistance of the modified coating were 25.1%, 34.1% and 32.4% higher than those of unmodified coatings, respectively. Moreover, the flexibility of the coating was significantly improved. The compression-bend ratio of the modified coating was 7% higher than that of the unmodified coating. The impermeability of the modified coating was 53% higher than that of the unmodified coating. The bond strengths of the modified coatings with a concrete and an acid-resistant ceramic tile were 3.08 MPa and 5.84 MPa, respectively, which were higher than the standard value of 1.2 MPa. SEM analysis showed that the morphological structure of the coating was changed. The results showed that a dense micro-structure with an interpenetrating network was formed. EDS analysis showed that the sulfur atom was absent in the modified coating after acid storage. The MIP test showed that the porosity of the modified sample decreased and the pore distribution was improved. TGA analysis showed that the modified coating could meet the requirement of temperature resistance at 250 °C.