Synthesis And Performance Research On Organic Siloxane Modified Acrylic Emulsion

Poly (siloxane-acrylate) emulsion has advantages both of polyacrylate and silicone. Compared with the polyacrylate emulsion, incorporation of silicone components with polyacrylate can much improve the water resistance、dirt resistance、heat resistance and mechanical strength of the corresponding latex film, which is very useful in many application fields.Although the synthesis of polysiloxane modified polyacrylate latex has been well concerned, it should be point out the the most commonly used synthesis methods are only capable for the latex with low silicone content. Obvious floating oil is generally observed in the emulsion using high silicone content, and the transmission on the latex film would sharply decrease because of the dramatically large-scaled phase separation. In this dissertation, we aimed to the synthesis of stable poly (siloxane-acrylate) latex with relatively high siloxane content. A one-pot-two-step emulsion polymerization method was put forward. In this method, cyclosiloxane firstly copolymerized with coupling monomers via a ring-opening polymerization (ROP) carried out in emulsion condition. The emulsion ROP reaction was followed by the free radical copolymerization reaction of acrylate monomers which were sequently added in the system together with the initiators. The influence of the synthesis condition especially the coupling agents was systematically studied. Stable poly (siloxane-acrylate) latex has been successfully synthesized with the silicon content as high as40%and the application performance of the latex as waterborne coatings has also been explored. The main research works are as follows:1. Monomer A was used as the monomer and the influences of emulsifier, initiator, functional monomer, polymerization protocol on the polymerization as well as the properties of the polymer latex emulsion studied in detail. On the basis of above-mentioned research, the influence of silane coupling agent structure and content on polymerization stability of the one-pot-two-step method was investegated. Alkylsilane (ALKYLSILANE-B) was chosen as silane coupling monomer with polymerization proceeded with good stability, high organosiloxane conversion rate, no floating-oil and no obvious phase separation.2. The structure of copolymer, morphologies and particle size distribution of latex particles were characterization by Transmission Electron Microscope(TEM)、Fourier Transform Infrared Spectroscopy (FTIR) and dynamic light scattering(DLS).etc respectively. The further researches about the influence of ALKYLSILANE-B content on the properties were studied. The results showed that the when the content of AYLSILANE-B was4wt%, stable emulsion with monomer A content as high as40%can be prepared. The transmittance of visible light of the latex film was to91%under400-800nm wavenumber. No large scaled phase separation of the latex particles or the films can be observed. The storage stability of the synthesized emulsion was up to six months. Continuous latex film can be formed at ambient temperature. With the increasing content of monomer A, the water contact angle of the latex was also increased.3. Waterborne coatings using the synthesized latex as the matrix were also prepared. After the addition of water-based adhesive curing agent the film adhesion on glass substrate was up to level1and with excellent resistance to water.