Correlation of Silicone Incorporation into Hybrid Acrylic Coatings with the Resulting Hydrophobic and Thermal Properties

• Published in: Macromolecules 2008-11, Vol.41 (22), p.8537-8546
• Main Authors: Rodríguez, Raquel, de las Heras Alarcón, Carolina, Ekanayake, Piyasiri, McDonald, Peter J, Keddie, Joseph L, Barandiaran, María J, Asua, José M
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Inorganic and organomineral polymers; Physicochemistry of polymers; Preparation
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma8006015

A series of high-solids hybrid silicone−acrylic latexes, with varying silicone concentrations and reactivities, was prepared via miniemulsion polymerization. The properties of the resulting coatings have been correlated with their structure and the extent of silicone grafting. The highest silicone incorporation was obtained with silicones containing two reactive vinyl groups polymerized by a semicontinuous method with a delayed addition of neat monomer. It was found that the amount of silicone grafted to the acrylic chains, not the overall total amount in the formulation, was the main factor affecting film properties. Hydrophobicity, water resistance, and thermal stability all increased with the amount of grafted silicone. Coatings that contained high levels of nongrafted silicone displayed separate submicrometer silicone phases and exhibited inferior properties. When silicone was incorporated into the acrylic particles, the total drying time of the coating was shorter, and the water distributionas determined with magnetic resonance profilingwas more uniform, in comparison to an acrylic coating. A blend of a silicone emulsion and the acrylic latex displayed a nonuniform water distribution at later times with significantly slower dryingindicative of the formation of a “skin” layer consisting of coalesced silicone droplets. Thus, incorporation of the silicone within the acrylic particles offers clear advantages in the film formation process. These results indicate that the hybrid latex is superior for coatings in comparison to the acrylic or to blends of the acrylic with silicone.