The Preparation And Properties Of Waterborne Damping Coatings

Waterborne polyurethane has excellent performance and is widely used. The modification by acrylate can improve its water resistance, weather resistance, the solids content and productivity of polymer. Nano-SiO2 has some advantages, such as high surface area, high temperature resistance, thickening property and with many hydrophilic groups in its surface, which means nano-SiO2 is easy to be modified so that the dispersion in polymer emulsion can be improved. This paper studied the preparation of polyurethane the modification by acrylate nano-SiO2. The main contents of the paper are as follows:1. This article chose 4,4’-Methylenebis(phenyl isocyanate) (MDI) and Poly(tetrahydrofuran) (PTMG) as the main monomers,1,4-Butanediol (BDO) and 2,2-Bis(hydroxymethyl)propionic acid (DMPA) as chain extender to prepare polyurethane prepolymer, and with Triethylamine (TEA) as a neutralizer, deionized water as the emulsifier, anhydrous ethyl diamine as chain extender to prepare polyurethane emulsion. This part explored effect of the MDI concentration r and molar ratio of -NCO and-OH on properties of polyurethane. From the results of Dynamic Mechanical Analysis (DMA), when R=1.5 and r=0.45, damping factor of film was the highest at both low temperature and high temperature, and film storage modulus was maximum. It can be seen from results of Thermogravimetric Analysis (TG), polyurethane thermal stability increased with the increase of R and r. Atomic Force Microscope (AFM) images showed that as r increased the roughness of films decreased.2. The effect of mass ratio of MMA and BA and prepolymer on damping properties was explored first. When the molar ratio of MMA and B A is 1:1, the effects of mass ratio of acrylic ester on the damping properties of copolymers were explored. Results of DMA showed, when the mass ratio was 10:90, damping properties of copolymer improved the most and the curves varied between 0.42-0.45.3. When ratio of Methyl methacrylate (MMA) and butyl acrylate (BA) and propolymer was 10:90, copolymer performance was studied when ratio of MMA and BA changed. Water resistance property, alkali resistance property and solvent resistance property of polyurethane were significantly improved by the modification of acrylic ester. According to the results of DMA, when the ratio of MMA and BA was 80:20, the damping properties of copolymers were well within the range of 30-80 ℃, maximum value of its Tan δ was at 0.53, but storage modulus decreased to 10MPa. It can be seen from TG that thermal stability of copolymer enhanced when acrylic was introduced. With the content of BA enhanced the stability of copolymer and the roughness of the film increased judging from the AFM image.4. In this article, surface of nano-SiO2 was modified through (3-Aminopropyl) triethoxy silane, damping properties was studied when the content of SiO2 changed. The DMA showed that when the content of SiO2 was 6% damping factor the composite was up to 0.46, but storage modulus reduced compared with polyurethane.