Preparation Of Waterborne Acrylic Resin Microcapsules And Study On The Restorability Of Wood Coatings

As a natural polymer composite material,wood material has unique texture,color and texture,which is a common green resource in nature.The surface treatment of wood materials with wood coatings can form a dense and even film on the surface,which plays a role of protection and beautification.However,in the long-term use of the coating,due to the change of environmental factors,the lack of toughness of the coating and other factors,micro cracks will occur in the interior of the coating and then expand,or even destroy the overall structure of the coating,thus affecting the service life of the coating and wood.As a new effective way to restrain microcracks,self-healing technology has become a research hotspot in many application fields.In this paper,the most widely used waterborne acrylic coating in wood coatings was selected as the research object,and the microcapsule self-healing technology was applied to the waterborne coating on wood surface for experimental research.Two kinds of core materials were selected to prepare and optimize urea formaldehyde resin coated waterborne acrylic resin microcapsules.The effects of core-wall ratio,concentration and coating process on the coating performance were studied.The aging resistance of waterborne coating with microcapsules was tested to characterize the crack suppression effect.The main conclusions are as follows:(1)In this paper,two kinds of waterborne acrylic resin microcapsules,Dulux and Nippon,were prepared by in-situ polymerization.Through the control of the core-wall ratio,water bath temperature and depositing time of the two microcapsules,the microcapsules with different yield,particle size,coating rate,morphology and chemical structure were obtained.The best preparation process of the two microcapsules was determined as follows: water bath temperature was 70 ?,depositing time was 5 days;the most important factor affecting the performance of the microcapsules was the core-wall ratio.(2)The core-wall ratio was used as a variable to prepare microcapsules with different core-wall ratio.The results showed that the performance of Dulux waterborne acrylic resin microcapsules with core-wall ratio of 0.58:1 and Nippon waterborne acrylic resin microcapsules with core-wall ratio of 0.67:1 were better.The two kinds of microcapsules were deposited for different times.With the increase of the depositing time,the microcapsule particles gradually increased,and with the phenomenon of adhesion,but the microcapsules would not be completely deposited and agglomerated because of the depositing time too long.(3)To explore the effect of the concentration of microcapsules with different core-wall ratio on the performance of the film.The microcapsules with different core-wall ratio and different concentrations were added into the waterborne coating.The optical properties,mechanical properties and liquid resistance of the film were tested,and the microstructure and chemical composition of the film were characterized.The results showed that when the core-wall ratio of Dulux waterborne acrylic resin microcapsule was 0.58:1 and the concentration was 10.0%,the comprehensive performance of the waterborne primer and topcoat film was the best.When the core-wall ratio of Nippon waterborne acrylic resin microcapsule was 0.67:1 and the concentration was 10.0%,the comprehensive performance of waterborne primer and topcoat film was the best.(4)Based on the determination of the best core-wall ratio and concentration,the effects of primer number,topcoat number and microcapsule adding method on the film performance were studied.Dulux waterborne acrylic resin with core-wall ratio of 0.58:1 and concentration of 10.0% was added into the coating.The film was prepared by different coating processes.The coating process of “primer 3 times,topcoat 2 times,microcapsule added in the primer” had the best performance.At this time,the color difference was 0.9,gloss was 29.1%,hardness was 3H,adhesion was 0 level,impact resistance was 11 kg·cm,elongation at break was 29.78%,and the film had good liquid resistance and micro morphology.Nippon waterborne acrylic resin with core-wall ratio of 0.67:1 and concentration of 10.0% was added into the coating,and the film was prepared by different coating processes.The coating process of “primer 2 times,topcoat 3 times,microcapsule added in the primer” had the best performance.At this time,the color difference was 0.9,gloss was 23.2%,hardness was 3H,adhesion was 0 level,impact resistance was 12 kg·cm,elongation at break was 26.31%,and the film had good liquid resistance and micro morphology.(5)The film stability and aging resistance of the two kinds of microcapsules were studied.It was found that the color difference and gloss of the film without microcapsules were more obvious than those with microcapsules.In different environments,the film without microcapsules was destroyed more obviously.Different aging environments had no effect on the composition of the film.The film with microcapsules had good stability and aging resistance,which showed that Dulux waterborne acrylic resin microcapsules and Nippon waterborne acrylic resin microcapsules can repair the film to a certain extent.