Synthesis, Characterization And Properties Of Modified Waterborne Acrylic Latexes

Acrylic latexes have been widely applied in water-based coatings, printing ink and adhesives oweing to their environmental aspects, low costs, as well as excellent film forming abilities, decorative properties and regulation performance, and so on. However, conventional waterborne acrylic latexes can not meet the needs of some special applications because of their inadequacy properties/deficiencies of water resistance, chemical resistance and heat resistance, etc. In order to obtain good performance, modification methods including grafting, copolymerization, crosslinking and blending have been used to modify the acrylic latexes. The functional modification method is mostly used for this purpose, and received highly attentions recently. In this paper, different functional monomers were used to synthesize a series of modified waterborne acrylic latexes by copolymerization or crosslinking method. The main contents and conclusions of this paper are as follows:1. Allyl polyeylene glycol(APEG) modified acrylic latexes. APEG was used to copolymerize with acrylic monomers to synthesize the APEG modified acrylic latexes for two-component coating. The results showed that the APEG acted as vinyl monomer as well as nonionic surfactant in the copolymerization process. While increasing the APEG dosage from 0% to 10%, the monomer conversion and the average particle size of latexes almost keep unchanged, but the stability of modified latex increased for the gel ratio reduced from 3.2% to 0.5%. Meanwhile, the film showed increased elongation at break and thermal stability, but decreased water resistance and mechanical properties. When the latexes were applied in two-component coatings, the crosslinking reaction were took place between the hydroxyl groups provided by APEG and the hexamethylene diisocyanate trimer. As a result, the films were obtained with improved properties such as water resistance, mechanical properties and thermal stability.2. Epoxy modified acrylic latexes containing carboxyl groups. The modified acrylic latexes have have been synthesized by emulsion polymerization different amout of glycidyl methacrylate(GMA) and fixed amout of butyl acrylate and methyl methacrylate via three addition modes of GMA. The results showed that the stable latexes with core-shell structure were synthesized, and the GMA dosage and addition method have great effects on the performances of latex and film. With a higher GMA content, latexes with higher content of coagulum and bigger-sized particles were obtained. Meanwhile, the higher crosslinking extent was formed in the film. As a result, the crosslinking provided the films with improved/better mechanical properties, water resistance, chemical resistance, and thermal stability. Under the same of GMA content, the latexes and films have better performances when GMA was introduced at latter stage.3. Fluorinated modified acrylic latexes were synthesized by copolymerizing dodecafluoroheptyl methacrylate(DFHMA) with butyl acrylate and methyl methacrylate. The surface hydrophobic performance of the film was greatly improved because migration and enrichment of DFHMA on the film surface. With increasing of the DFHMA dosage, viscosity of the latexes increased, the surface hydrophobic performance, water resistance, chemical resistance, and thermal stability of films were greatly improved.