Preparation And Film-Forming Investigation Of Polysilsesquioxane Emulsion Modification Of Composite Polyacrylate Emulsion

Polyacrylate (PA) latex currently widely used as water-borne coating. The latex of PA is one of the popular waterborne resins, which can provide many specific properties, such as good film-forming ability, transparency, and flexibility. However, there are some disadvantages on the pure PA latex film, such as the low hardness, poor water resistances, and poor thermostability. Polysilsesquioxanes (PSQ) is recognized as an intermediate between silica and siloxane. The characteristic properties made PSQ attractive as good modifiers for waterborne coatings to compensate the disadvantage of polymer latex. In present dissertation, we prepared aqueous PSQ latexes in the existence of small amount of emulsifiers and catalysts. We further modified polyacrylate latex by using PSQ latex with different process. The as-synthesized composite latexes have potential industrial application as a matrix for waterborne coatings. The main research works are as follows: (1) Polysilsesquioxane (PSQ) particles with different organic functional groups, such as methyl (PMSQ), phenyl (PPSQ), and vinyl (PVSQ), were prepared via hydrolysis and condensation reactions of various organotrialkoxysilane precursors in water. We can obtain PSQ latexes with controllable particle size and narrow distribution, by changing the amount of catalyst and emulsifer. In order to introduce the reactive functionalities for the next graft reaction, the particle surface of PPSQ and PMSQ were further modified by using γ-methacryloxypropyltrimethoxysilane(MAPTS).(2) These PSQ functionalized by polymerizable groups were used for the further seeded emulsion copolymerizations of methyl methacrylate (MMA) and butyl acrylate (BA). The DLS and TEM characterization results indicated that both the size and the morphology of the composite particles were influenced by the size and the surface functionality of PSQ seed, which were determined by the kind of precursor, the type and the amount of catalysts and emulsifiers, and the surface modification during the PSQ synthesis process. The composite latexes were available to form the continuous film under a moderate condition. And the performance of the PMSQ composite latex films were noticeably improved, such as hardness, water resistance, thermal stabilities, and flame retardance.(3) By different polymerization process, the different ways of PPSQ modified polyacrylate latex were studied. We studied modified polyacrylate latex by the characterization the morphology of latex particles, the thermostability and performance of latex film. The results show that compared with Pickering emulsion polymerization and physical blending process, PPSQ/PA and PA/PPSQ films performed the best film properties, which were prepared by seed emulsion polymerization.And the performance of the PPSQ/PA and PA/PPSQ composite latex films were also improved, such as hardness, water resistance, and storage modulus.