Preparation Of One-component Polyurethane Sealant

Building sealants, as an important class of building functional materials, play an irreplaceable role in ensuring the structural integrity of the building to extend the building life. Water and other media will soon result in corrosion and aging in the interface parts of the wall casting, until the structure of the stress failure, which will seriously affect the life and functions of buildings. The use of construction sealants for bonding and sealing cracks is the only way to solve this problem. Polyurethane(PU) sealant, which has a certain degree of flexibility, is a product with bonding and sealing performance. It can be used to fill gaps that shall be subjected to vibration or thermal expansion and cold contraction. PU also has other properties such as wear-proof, anti-aging, good elasticity, and strong bonding performance. However, most of the commercial polyurethane sealants face the problems such as high cost and the volume shrinkage. In this thesis, an organic/inorganic composite polyurethane sealant has been designed to obtain excellent performance and lower cost.According to the polymer theory, a novel series of one-component polyurethane/heavy calcium carbonate compound elastomer construction sealants were proposed. A series of polyurethane sealants were prepared and the list of raw materials was obtained. The effect of the contents of Isocyanate group on the performance of the final product was studied and the optimal reaction time was determined. The polyurethane formulations with high performance were determined by orthogonal experiments. The effect of calcium carbonate on the mechanical properties was investigated and the effect of the ambient humidity on the crossing linking network of the PU solidification was studied. The curing process was studied by a model and the effect of water and thermal on the properties was analyzed. The cost of the polyurethane sealant was calculate and a comprehensive comparison with silicone sealant was carried on.The result showed that the best time of synthetic prepolymer was 4～5h; As the isocyanate value of prepolymer increasing, viscosity of prepolymer decreased, cured tensile strength increased, elongation at break decreased. Along with amount of calcium carbonate increasing, the longitudinal strength and the elongation ratio at break reduced. Along with particle size of calcium carbonate decreasing, the longitudinal strength and the elongation ratio at break increased. The organic modified calcium carbonate was better than calcium carbonate; Ambient humidity had a great influence on the dry time of surface but has little influence on the crossing linking network. The Curing models showed that PU can form high density cross—linked network through the reaction between ureido and-NCO. The PU sealant not only showed several good properties but also cost lower than 12 Yuan/kilograms, so which may substitute silane sealant.