Study On The Modification Of Polyacrylate Emulsion Adhesive By Nano- CaCO₃

This paper is aimed at the modification of a traditional polyacrylate emulsion adhesive to overcome its shortages such as low solid content and poor alkali-resistance. After the modification, a novel adhesive with the application in glass fiber cloth coating was obtained, which has the property of non-conglutination and easy handling, so as to enhance the performance of the glass fiber mesh further. By in-situ dispersing nano-CaCO₃ powders in the acrylate monomers and emulsion polymerization, a novel CaCO₃/polyacrylate nanocomposite emulsion adhesive with possible core-shell structure was prepared. This composite emulsion adhesive was used as the coating of a glass fiber mesh. The coated glass fiber mesh showed greatly improved performances such as non-conglutination after drying and easy handling, which enlarges its application.The main contents of this study are as the follows. Hexadecyl trimethyl ammonium Bromide(CTAB) with different dosages were used as the surface modification reagents for the nano-CaCO₃ powders. The effect of different dosages on the settlement ratios of nano-CaCO₃ powders were discussed in detail. Different dispersion methods were used to compare the dispersion effects. It is found that the nano-CaCO₃ powders were uniformly dispersed in MMA, VAC, BA and other monomers by the in-situ dispersion. CaCO₃/ Polyacrylate nanocomposite emulsion adhesive with a possible"soft-core and hard-shell"structure was synthesized by seed emulsion polymerization. The polymeric parameters such as temperature, core-shell content ratio, the ratio of hard/soft monomer, the dosage of water and initiator, etc. were discussed in detail. The basic properties of the prepared composite emulsion adhesive were measured. Then it was coated on glass fiber cloth and the coating performances were tested.The optimum polymeric parameters are as follows. As the core material, MMA, VAC and BA were in the ratio of 1/2/7; while as the shell material, the relative ratio was 7/2/1. The ratio of core/shell content was 5/7. The NMA was about 10% of the monomers. The water was about 138% of the monomers. The emulsifier was 2.38% of the monomers. The initiator was 0.72% of the monomers. The reaction temperature is about 78℃. It was found that the mean diameter of the composite latex particles increased obviously with the increasing content of the nano-CaCO₃ powders. When the loading of nano-CaCO₃ powders was 2‰, there was no powder conglomeration during the polymerization process. The solid content and thermal stability of the composite emulsion adhesive were the highest compared with other nano-CaCO₃ powder loadings. In addition, the composite emulsion adhesive showed proper viscosity and good leveling. The coating performances of the glass fiber cloth were measured and the results were as the follows. When the loading of nano-CaCO₃ powders was 3‰, the cohesive force of the coated glass fiber mesh was only slightly higher than that of the 2‰loading mesh. The alkali-resistance performance was the best in the 2‰nano-CaCO₃ loading mesh, which was proved by the SEM micrographs too. Moreover, the coated meshes with 1‰and 2‰loading of nano-CaCO₃ powders showed excellent tacky adhesion property, which could reach to gradeâ… . Therefore, the mesh coated with the composite emulsion adhesive of the 2‰nano-CaCO₃ powder loading had the best overall performances.