| At present,water-based coatings have gradually replaced solvent-based coatings.Acrylic resin is commonly used in water-based coatings,but compared to solvent-based resins,the conventional acrylic resin has some disadvantages such as low hardness and poor water resistance.In this paper,a core-shell structure acrylate emulsion with hard core and soft shell was prepared by using particle design.The design method of high performance emulsion was studied and improved.Secondly,the core-shell structure acrylate emulsion was modified by self-crosslinking and nano-silica sol blending,and the properties of the modified emulsion and its film were studied.The stability of the composite emulsion and the properties of the emulsion film were studied.The results can provide the theoretical basis for the preparation of acrylate emulsion and waterborne coatings with excellent properties.The specific contents of the study are as follows:(1)A core-shell acrylate emulsion was prepared by pre-emulsification,semi-continuous and seed emulsion polymerization.The composition and core-shell ratio of core-shell structure acrylate emulsion and its film properties are studied.The results show that the core-shell structure has a significant effect on the properties of the emulsion and its film,the film properties of the emulsion can be controlled.By the design of its structure composition,the poly-acrylate emulsion,which can form film at room temperature and has better film performance.TEM shows that the latex particles have obvious core-shell structure.At the same time,the thermo-mechanical properties of the film show that both core and shell could control the mechanical properties of the film.(2)Self-crosslinking modification,the functional monomer DAAM was introduced into the poly-acrylate molecular chain,and ADH was added as the crosslinking agent,room temperature self-crosslinking acrylic resin emulsion was prepared.The effects of the addition of DAAM and its amount on the stability of the emulsion and the effect of the ratio of DAAM/ADH on the properties of the emulsion and its film were investigated by measuring method of emulsion stability,gel rate and water absorption,tensile strength and TG,etc..The results showed that the crosslinking efficiency of the crosslinked monomer DAAM was the highest when it was added in the shell layer.When the addition amount is 5%,the gelation rate of the emulsion polymerization process increases fastest;when the mass ratio of DAAM-ADH is 1:1,the film properties are the best.The tensile properties,hardness and TG of the film increase with the introduction of DAAM-ADH system.Therefore,self-crosslinking modification greatly improves the properties of emulsion film,and this method is feasible for the preparation of high performance emulsions.(3)KH560 and KH570 silica sol were prepared by sol-gel method.The composite emulsion modified by nano-silica sol was prepared by pHysical blending of the prepared silica sol and acrylate emulsion.The effects of different doping amount of nano-silica sol on the stability and film properties of composite emulsion were studied.The results showed that the storage stability of the composite emulsion was the worst with the increase of the content of nano-silica sol.When the doping amount is more than 3%,the tensile strength decreases;KH560 silica sol doping greatly increases the tensile strength of the coating film and reduces the water absorption of the coating film;the doping of two kinds of nano-silica sol,The thermal stability of poly-acrylate film was improved significantly.The properties of KH560 nano-silica sol is better,used as the modified material of polyacrylate. |
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