Encapsulation of non-chemically modified montmorillonite clay platelets via emulsion polymerization

This paper demonstrates that a covalent bonding between clay platelets and polymer chains is not necessary for a successful encapsulation of the inorg. compds. through emulsion polymn. In the work described in this paper, the chem. modification of clay was performed using two kinds of titanate coupling agents: titanium IV, (2-¿propanolato)¿tris(2-¿propanoata-¿O)¿, 2-¿(2-¿methoxyethoxy) ethanol and titanium IV, 2-¿propanolato,¿tris(isooctadecanoato-¿O)¿, where the former is satd. and the second has unsatd. alkyl groups. The hydrolytic stability of the organoclays thus synthesized was thereafter investigated. It was found that the titanate modifiers were highly sensitive towards hydrolysis as evidenced by Fourier transform IR and thermal gravimetry analyses. The effect of a chem. modification step on clay encapsulation was studied by comparing the results obtained between reactions using the synthesized organoclays and the ones using native clay platelets. It was found that the incorporation of polymerizable double bonds on clay platelets was unnecessary to achieve successful encapsulation and that, surprisingly, the chem. modification step could be omitted for the synthesis of clay-¿contg. latex particles. The effects of monomer feed compn., i.e., monomer mixts. consisting of different wt. ratios Me methacrylate¿/butyl acrylate, and process types on clay encapsulation were also investigated. Both parameters were found to have a strong influence on clay encapsulation. Finally, the surfactant concn. and the surfactant type were statistically found to have a significant effect on the clay¿/polymer interaction as evidenced by the results of glass transition temps. of dried latex¿/clay nanocomposites powders