Preparation Of Hybrid Latex Particles By Pickering Emulsion Polymerization And Their Film Properties

Compared with traditional solvent-based paints,latex paints use water as solvent,which are non-flammable,non-explosive,environmentally friendly,have high production safety,and have high adhesion on substrates such as cement,metal and wood.Based on the above advantages,water-based emulsion coatings represented by latex paints have been widely used.At present,industrial emulsion polymerization requires the use of large amounts of surfactants.After the polymer emulsion forms the coating,the residual surfactant molecules in the coating will greatly reduce the water resistance and gloss of the coating,so that the service life of the coating will be reduced.Pickering emulsion polymerization technology uses solid particles as emulsion stabilizer,which can greatly improve the water resistance and mechanical properties of the latex film.At present,there is still a lack of systematic research on the influencing factors and polymerization mechanism of Pickering emulsion polymerization,and the adsorption mechanism of solid particles is still unclear.In view of the above key scientific issues,this topic uses silica nanoparticles as solid stabilizers to prepare hybrid latex particles by Pickering emulsion polymerization,and systematically studies the factors affecting the adsorption of inorganic particles and the physical properties of hybrid films.The main research contents are as follows:1.First,silica nanoparticles with a size of 50 nm were prepared by the Stober method,and the silica nanoparticles were introduced into the Pickering emulsion polymerization system in the form of powder and sol,respectively.The silica particles were used as Pickering emulsion polymerization solid stabilizers,and conduct emulsion polymerization to prepare hybrid latex particles.The effects of silica nanoparticle state,pH value,initiator type,and reaction monomer type on the morphology of hybrid particles were explored.The results show that the dispersibility of silica particles in water has an important influence on the morphology of hybrid latex particles.At the same time,the interfacial tension between the monomer and water has a greater impact on the adsorption of silica particles on the polymer surface,and silica nanoparticles are more easily adsorbed on the surface of the polymer latex with higher interfacial tension.Subsequently,the cationic monomer 2-(methacryloyloxy)ethyltrimethylammonium chloride(MTC)was introduced as an auxiliary monomer to participate in the styrene Pickering emulsion polymerization,in order to promote the adsorption of silica nanoparticles on the surface of polymer latex particles.The surface morphology of the hybrid latex particles was the best when the pH of the system was 11 and the MTC concentration was 8 wt%.2.Second,silica sol(Ludox TM-40)was used as Pickering stabilizer,and hybrid latex particles were prepared by Pickering emulsion polymerization to explore the experimental factors affecting the adsorption of inorganic nanoparticles on the surface of polymer latex.Hybrid latex particles were prepared by using MMA as the monomer,and the hybrid latex particles with uniform particle size and raspberry-like hybrid structure were prepared near pH=5.5.It was confirmed that pH has an important effect on the adsorption of silica nanoparticles on the surface of polymer latex.In the case of initiating polymerization,lowering the reaction temperature is beneficial to increase the adsorption amount of silica particles.When the sodium ion concentration in the reaction system was controlled at 5 mM,the adsorption amount of silica particles reached the maximum value,exceeding 25 wt%.Hybrid latex particles were prepared by Pickering emulsion polymerization with different monomers.The hydrophilicity and hydrophobicity of monomers will also affect the adsorption of inorganic particles on the surface of latex particles.Hydrophilic monomers are beneficial to improve the adsorption efficiency of inorganic particles on the surface of latex particles.3.Finally,Ludox TM-40 silica nanoparticles were used as Pickering emulsion polymerization stabilizer,P(MMA-co-BA)/SiO2 hybrid latex particles with a particle size of 400 nm and a narrow particle size distribution were successfully prepared by one-step method,to investigate its film-forming properties.By introducing the monomer butyl acrylate(BA)into the polymerization reaction system,the glass transition temperature of the hybrid latex particles was lowered to-14℃,so that the polymer hybrid latex could form a film at room temperature.The effect of different MMA/BA ratios on the properties of the hybrid films was investigated.When the mass fraction of BA in the polymer is 40-45%,the film-forming properties of the hybrid emulsion are the best.The heat resistance of P(MMA-co-BA)/SiO2 hybrid latex films is good,and the thermal decomposition temperature of the films is about 300℃.For the hybrid latex particles prepared with different MMA/BA ratios,the loading rates of silica nanoparticles were all above 20 wt%.The light transmittance of the hybrid film can reach 88%,and the hybrid emulsion remains stable within 48 hours after dilution.The water resistance and water absorption tests showed that the water resistance of the hybrid latex films prepared by Pickering emulsion polymerization was significantly better than that of the hybrid latex films prepared by emulsion polymerization using surfactants.