Preparation Of Water-based Acrylic Clearcoats And Study On The Film Properties

With human paying great attention to environmental protection, low VOC emissions of water-based paint and high solids coatings and powder coatings of zero-pollution is becoming the mainstream of development of the world paint, powder coatings and high solids coatings were limited application due to the special construction techniques, therefore, the water-based paint is becoming the protagonist of environmentally freidlly coatings market.Acrylic resin has excellent light resistance and weather resistance, good durability of outdoor exposure, not easy to decompose and turn yellow under UV irradiation, it could maintain original gloss and color for long term and has good heat resistance、corrosion resistance、chemical resistance and excellent performance of decorative and protective, so it has become the most popular resin in coating industry.Nano-materials have small size effect, surface effect, quantum size effect and macroscopic quantum tunneling effect, adding them to paint can greatly improve the impact resistance、adhesion、resistance to aging、corrosion resistance、UV resistance and other properties of film.Aqueous acrylic resin was synthesized in this work, using it and crosslinker amino resins made of water-based automotive clearcoats and adding nano-silica to modify, the main contents include the following aspects:1Effect of molecular weight of resin on film propertiesWhile molecular weight of resin is low, its viscosity is small, the crosslinking reaction can occur, but because of low molecular weight, poor performance of film, in contrast, while molecular weight of resin is high, its viscosity is big, the crosslinking reaction could not occur adequately.2Effect of different solvent of resin on film propertiesPropylene glycol monomethyl ether and isopropyl alcohol by volume ratio of2:1as the solvent and n-butyl alcohol and isopropyl alcohol by mass ratio of1:1as the solvent, results show the film using the first solvent do have better performance than the second, this shows the first solvent have better solubility for acrylic resin, so cross-linking reaction occurs more fully.3Effect of different monomer concentration of resin on film propertiesFilms were prepared with monomer concentrations of resin were75%,70%,65% and60%, respectively, it was found that when monomer concentration is low, the crosslinking reaction occurs more fully, but reduces the monomer concentration, also means the VOC emissions increase, therefore, the monomer concentration should not be too low.4Effect of mixing high and low molecular weight of resin on film propertiesHigh molecular weight resin and low molecular weight resin ratio of20/80,30/70,40/60,50/50were mixed, and the crosslinking groups on the high molecular weight of the resin increases one times, so as to make the cross-linked network structure more compact to promote the performance of film, it was found that the chemical resistance of the film of resin mixing ratio is20/80has been greatly improved, but the mechanical properties are still unqualified, reason is that the crosslinkage of film is too high, so reduce amount of crosslinking groups on low molecular weight resin, the amount of crosslinking agent also reduce appropriately, the film finally has excellent mechanical properties and chemical resistance.5Effect of different nano-silica content on film properties0.5%,1%and2%nano-silica of film forming matter weight were added clearcoats, part of nano-silica were conglomerated in2%nano-silica content of clearcoats one hours after dispersing, the hardness of film of0.5%nano-silica content increases, but the impact strength decreases, the hardness and impact strength of filmof1%nano-silica content both decreases, chemical resistance of two film both decreases, this result shows experiment of adding nanoparticles to modify is not successful.