Synthesis And Performance Research On Silicone/Polymer Composite Latex

Due to the excellent performance of both silicone and polymer materials, silicone/polymer composites have attracted more and more researchers' attention. Silicone can be introduced into emulsion polymerization, which incorporates with organic polymers like polyacrylate (PA) and/or polystyrene (PS) for the preparation of composite latex. The composites are widely used in the field of high-performance water-based coatings, functional coatings and other environmentally friendly composite emulsion. In this dissertation, we prepared polydimethylsiloxane (PDMS)/polyacrylate (PA) latex with high silicon content via two step emulsion polymerization method by using the well selected coupling agent system. Further, we prepared polymerizable double bond modified polysilsesquioxanes (PSQ) nano and submicron particles with fluorescence and introduced them into the emulsion polymerization to prepare PSQ/PS) and PS/PSQ two kinds of core-shell latex particles with photoluminescence properties. The PS/PSQ and PSQ/PS composite latex can transformed into polymer coating with fluorescence properties and hydrophobic surfaces with the assistance of a small amount of PDMS latex. The main research works are as follows:1. Preparation of siloxane containing acrylate polymer latex for architectural coatings with small particle size, high conversion rate and high silicon content:By using octamethylcyclotetrasiloxane (D4) as the monomer, trialkoxysilane and dialkoxysilane as the reactive coupling agent system. dodecylbenzenesulfonic acid (DBSA) as the inisurf, and anionic & non-ionic emulsifier to work together, PDMS latex was synthesized via ring opening polymerization in emulsion. The PDMS latex was used as the seed for the following emulsion polymerization of methyl methacrylate (MMA), butyl acrylate (BA) and a-methyl acrylic acid (MAA), to prepare PDMS/PA composite latex. The synthesis conditions of the PDMS seed and composite latex were systematically studied, namely, time, charging way, composition and content of emulsifier/catalyst, coupling agent system and the content of PDMS. The influence of above factors on particle size, dispersion stability, conversion rate, and water resistance, heat resistance and mechanical strength of the corresponding coating films were discussed. Through the optimization of reaction conditions, the particle size of final PDMS/PA composite latex was controlled around 100 nm with good stability and high conversion rate. Architectural coatings was prepared using the PDMS/PA latex with different silicon contents, and the properties of the coating films were characterized and compared. It is found that the composite latex coating with high silicon content are specialized by the excellent adhesion, water resistance, and surface hydrophobicity of the coating films.2. The preparation of fluorescent latex particles without dyes and metal complexes:By using methacryloxy propyl trimethoxyl silane (MPTS), (3-aminopropyl) triethoxysilane (APTES) and tetraethoxysilane as co-precursor, polymerizable double bond modified PSQ particle dispersions were prepared via sol-gel process. The influence of the pH, the different contents of the precursors and other synthetic conditions on the particle size of the sol and photoluminescence properties was examined, and synthesis control over the particle size in the diameter range between 20nm to 500nm was realized by adjusting the synthetic parameters. PSQ sol with small particle size(<100nm) as Pickering emulsifier, PS/PSQ core-shell composite particles with fluorescence were synthesized by Pickering emulsion polymerization. Using PSQ sol with large particle size(>200nm) as seeds, PSQ/PS composite particles with core-shell structure and fluorescence were prepared by seed emulsion polymerization. The particle morphology, structure and photoluminescence properties were characterization by transmission electron microscope(TEM), surface energy spectrum (EDS), photoluminescent spectra (PL), laser confocal microscope (LSCM), Fourier transform infrared spectroscopy (FTIR), respectively./The composite particle morphology and its photoluminescence were systemically studied by changing the pH, the emulsifier, the initiator, the sol content and reaction process related factors.3. The preparation of functional coatings with fluorescent properties and hydrophobic surfaces:Polymer coating films were formed by using PSQ/PS and PS/PSQ as the film formation resin blended with small amount of PDMS latex, respectively. We explored the influence of PDMS latex, the structure of fluorescent latex particles and post-processing temperature on the coating films, which was revealed by the surface contact angle and morphology study. The coating films showed blue fluorescence excited under UV light, and the contact angle of coatings of PSQ/PS can reach to 127.6° with 5wt% addition of PDMS dispersion.