Study On Polymerzation And Performance Of Silica Sol-Polyacrylate Compostie Latex

The composite materials of polymer and inorganic compound are of important parts in the field of science and technology of materials. The process to make the hybrids is the one of most important methods in the preparation of the high performance polymer material. Polyacrylate's good processability.plasticity and functionality makes it is one of the best carriers of hybrid materials.This paper developed a new method for producing silica sol/polyacrylate composite latex. The new point was to use the product of hydrolyzed and condensated TEOS instead of the commercial silica sol. In this paper the preparation and properties of silica sol/polyacrylate were stuied. The TEOS was first hydrolyzed and condensated to become silica sol, and then MMA and BA were initiated by cationic thermal initiator and anionic thermal initiator respectively. The influence of the experimental conditions.containing the type and amount of initiator.the amount of TEOS.the reaction temperature, the pH value,the adding speed of monomer,the stirring speed, on the properties of emulsion. At the same time, the structure of latex particles were analyzed by transmission electron microscopy and fouier transform infrared spectroscopy (FTIR).The optimal synthesis conditions in the system of cationic thermal initiation were listed as follow:w(MMA):w(BA)=2:3,w(AIBA·2HCl)=0.42wt%～0.48wt%,w(TEOS)=9wt%～3wt%, T=75℃in the polymerization process, pH=5.7-6.5 in the polymerization process,v(monomer droplet)=ldrop/1s,v(stirring)=350r/min in the hydrolysis and condensation process of TEOS, v(stirring)=300r/min in the polymerization process,v(stirring)=180r/min in the heat preservation process. Electron spectroscopy imaging by transmission electron microscopy (TEM) studies revealed a well-defined core-shell morphology for these particles, and the core is silica sol and the shell is polyacrylate. The fouier transform infrared spectroscopy (FTIR) spectrum showed that there were chemical bonds between silica sol and polyacrylate. This also showed that the organic monomers were polymerizing on the surface of silica sol. With the increase of TEOS amount, the stability of the emulsion and the hardness of the film increase. But the emulsion will deposite and the film will crack with excessive TEOS. Experiments showed that the optimal amount of TEOS is 9wt%-13wt%.The optimal synthesis conditions in the system of antionic thermal initiation were listed as follow:w(MMA):w(BA)=2:3, w(KPS)=0.32wt%-0.40wt%, w(TEOS)=6wt%-10wt%,T= 80℃in the polymerization process, pH=6.8-7.5 in the polymerization process,v(monomer droplet)=1 drop/1 s,v(stirring)=350r/min in the hydrolysis and condensation process of TEOS, v(stirring)=300r/min in the polymerization process, v(stirring)=180r/min in the heat preservation process. Electron spectroscopy imaging by transmission electron microscopy (TEM) studies showed that the silica sol in the emulsion were existing in the free form. This also showed that there was no chemical bond between the silica sol and polyacrylate.Compared with the silica sol/polyacrylate compostie lates initiated by the cationic thermal initiator and the silica sol/polyacrylate compostie lates initiated by the anionic thermal initiator,the mechanical stability, freeze-thaw stability, calcium ion stability, dilution stability and storage stability of the fomer were better than the later. This proved again that there was no chemical bond between the silica sol and polyacrylate,and the silica sol would deposited in the external prssure.