Preparation And Study Of Sulfur / Carboxylic Acid Mixed High Solid Waterborne Polyurethane / Nano - SiO 2 Composite Composites

Waterborne polyurethane materials, possessing the advantages of fire-retardant, low pollution, easy saving, convenient to use, as well as the low temperature resistance and flexibility, have become an important research in the polyurethane field. The unique excellent performance of nano composites provide new technique and route for all kinds of materials to achieve high performance and functionalization. The introduction of nano-silica in the aqueous polyurethane, we can prepare a comprehensive performance of nano-silica modified waterborne polyurethane hybrid emulsion.In this paper, we can use alkali metal silicates in acid-catalyzed and strong acid weak base salt in the double hydrolysis conditions by means of combination of precipitation and extraction prepared Nano silica dispersions. Reducing the surface of nano-silica hydroxyl, droping the surface energy of the particle surface and Weakening reunion between the nano-silica particles; the nano silica uniformly dispersed in the polyether (ester) diol, the dispersion directly as the raw materials to synthesis a series of carboxylic/sulfonic acid mixed type of waterborne polyurethanes, which solid content is up to50%. Using infrared spectrometer(FT-IR), thermogravimetric analyzer(TGA), X ray diffraction(XRD) and tensile strength methods to analysis the waterborne polyurethane.1. X-ray diffraction display modification of nano-SiO2particles before and after with no fixed patterns, and nano-SiO2surface morphology did not change its internal. Using nano-particle size and zeta potential analyzer display the average particle diameter of silicane coupling agents modified nano silica polyether(polyester) dispersion is50nm, FT-IR shows that nano silica have been linked up with the polyether(polyester) dispersion.2. Nano silica dispersion directly as raw materials of polyurethane, prepared a series of nano silica modified carboxylic/sulfonic acid mixed type of waterborne polyurethanes hybrid emulsion. With the increase of the amount of nano silica, the emulsion gradually change from milky to turbid, the stability of emulsion drop, the film hardness increases and water absorption of the composite film reduces. When the solid content of nano silica by amount of3%prepolymer, the pencil hardness and water absorption of the composite film is up to2H and reduce to6.5%, respectively.3. With the increase of the amount of nano silica, tensile strength polyurethane coating film the first increased and then decreased, while the elongation always decreased.With the increase of the amount of nano silica2%of the prepolymer, the tensile strength reached20MPa.4. When the content of nano SiO2from0to2%of the prepolymer, the thermal stability of the waterborne polyurethane coating films with increasing SiO2nanoparticles enhanced, and when the nano-SiO2content of more than2%of the prepolymer, the thermal stability of the coating films with the increase of nano-SiO2weakened.With the increase of the amount of nano silica2%of the prepolymer, the decomposition temperature of hard segment and soft segment reach330℃and400℃respectively, at this point, the thermal stability of waterborne polyurethane film is best.