Preparation And Characterization Of Acrylic Polymer Emulsion For Polypropylene Coating

With the performance improvement of synthetic materials, plastic has gradually replaced steel, leather and other materials and become an important material. Polypropylene, as one of five general-purpose plastics, is now widely used in many fields because of its good performance and low price. The development of polypropylene promotes the development of polypropylene coating. Polypropylene is non-polar material with low surface energy, so it is difficult for waterborne coating to adhere to it. Improving the adhesion of waterborne coating on polypropylene substrate becomes the critical issue for developing polypropylene coating. In this paper, isobornyl acrylate and organic silicone monomers, which can improve the adhesion of the emulsion on untreated polypropylene substrate were used as two key monomers to prepare acrylic polymer emulsions for untreated polypropylene coating. The main studies are as follows:(1)A core-shell acrylic polymer emulsion for untreated polypropylene coating was synthesized with butyl acrylate(BA) /butyl methacrylate(BMA) as core monomers, isobornyl acrylate(i BOA) /butyl acrylate(BA) /acrylic acid(AA) as shell monomers. Firstly, the effect of the hydrophilic property of the core monomers on the structure of the latex particles was investigated. Then the effects of polymerization condition, such as the polymerization temperature, the content of emulsifier and initiator, on the emulsions and the latex films were explored. The results showed that the emulsion with good polymerization stability and storage stability, high monomer conversion could be obtained when the polymerization temperature was 80℃, the content of the emulsifier and initiator were 3wt%, 0.5wt% respectively.(2)The effects of the content of AA on the structure of the latex particles, the surface tension of the emulsions, the contact angle of the emulsions on untreated polypropylene substrates were investigated. The results showed that AA was conducive to prepare normal core-shell latex particles. When the content of AA was 5wt%, the latex particles had clear core-shell structure, the emulsion had low surface tension and good wettability, the contact angle of the emulsion on untreated polypropylene substrate was small.(3)The effects of the content of i BOA on the surface tension of the emulsions, the contact angle and adhesion of the emulsions on untreated polypropylene substrates, mechanical property and thermostability of the latex films were investigated. The results showed that i BOA was conducive to improve the wettability and adhesion of the emulsions on untreated polypropylene substrates. When the content of i BOA was 45wt%, the surface tension of the emulsion and the contact angle of the emulsion on untreated polypropylene were small, the adhesion was 2 grade. In addition, i BOA improved the waterproof, tensile strength and hardness of the latex films.(4) Organosilicone was used to modify the acrylic polymer emulsion. Firstly, the effects of the organosilicone type and addition way on the polymerization stability were investigated. Then the effects of the content of vinyl triisopropoxy silane(AC-76) on polymerization stability, waterproof, Tg, surface morphology, thermostability and mechanical property of the latex films were investigated. The results showed that AC-76 improved the waterproof, Tg, surface smoothness, thermostability and mechanical property of the latex films. Moreover, AC-76 was conducive to decrease the surface tension of the emulsions and the contact angle of the emulsions on untreated polypropylene substrates. When the content of AC-76 was 2wt%, the performances of the emulsion were excellent and the adhesion of the emulsion on untreated polypropylene substrate was 1 grade. The emulsion can be used for untreated polypropylene coating.(5) The surface energy and dispersion force of the polymers were measured by Owens two liquids method. The adhesion mechanism of coating on untreated polypropylene substrate was investigated briefly. The study found that i BOA and AC-76 improved the adhesion of the emulsion on untreated polypropylene substrate by decreasing the surface energy of the polymer and increasing its dispersion force.