Study On Properties Of Nano-particles/Polyacrylate Emulsions Cured At Room Temperature

Polyacrylate polymer emulsions are widely used in coatings,adhesives and so on due to their good lightfastness, acid-alkali resistance and corrosion resistance. But it also has some disadvantages, such as high film forming temperature, low hardness, poor anti-after tack, poor water-resistant, low adhesion, etc. A series of acrylate polymer emulsions were prepared through the way of pre-designing particle and property of polymer, introducing a small quantity of functional monomer, selecting emulsification systems and initiation systems and emulsion polymerization technology. They can raise the ratio of performance to price of coatings and decrease VOC content in emulsion paint. Therefore, there are great meanings in theory and practice.Three kinds of emulsions with active carbonyl groups, including ketonic, aldehyde and acetoacetylate group have been prepared by copolymerization of styrene, acrylic acid, butyl acrylate and the corresponding functional monomer respectively. The film of polyacrylate emulsion can be cured at room temperature by dehydration reaction between a carbonyl-containing acrylic copolymer having an active aldo group or keto group and a hydrazine derivative having at least two hydrazino groups per molecule under the acid catalysis condition. The performance of the films was tested. The reaction parameters and the monomer composition on the properties of the films were mainly studied.Nano-silica/polyacrylate composite emulsion and MWNTs/polyacrylate composite emulsion were prepared by in-situ polymerization and blending methods respectively. The surface morphology, microstructure of the films were measured and analyzed by SEM, TEM and infrared spectrometer.It is shown that the water resistance, hardness, solvent resistance and gel content of the films obviously improved after crosslinking reaction. With the increasing content of crosslinking agent, the properties of the films continuously improved. But when excess crosslinking agent existed, the appearance, transparency and impact strength of the films decreased. The crosslinking reaction can be carried out under acidic condition and completed after 72h. The lower the initial pH, the faster the crosslinking reacted. The storage time of the emlusions can be prolonged by adding ammonia to adjust the pH value to 8.Nano-silica/polyacrylate composite emulsion prepared by in-situ polymerization had better performance. The hardness, water absorption and stain resistance of the films improved effectively. The emulsions exhibited best performance when the molar ratio of DS and OP-10 was 2:1 and the content was 2.5wt%, and nano-silica content was 9wt%. The addition of nano-particles can effectively improve the mechanical properties and water resistance of the films.The results of TEM showed that MWNTs/polyacrylate composite emulsion had better dispersibility after MWNTs carboxylation. The MWNTs dispersed homogeneously in the films and distributed on the fracture surface by single tube. The hardness, water resistance, adhesion of the films improved after MWNTs additon.