Preparation of Nanocomposite Polymer Latex

Abstract

Nanocomposite latexes of encapsulated TiO2 nanoparticles with core-shell morphology were successfully prepared through in situ miniemulsion polymerization of styrene / butylacrylate monomers onto the modified surface of TiO2 in a semi-continuous operation. Oleic acid was used to act as a coupling agent between TiO2 surface and polymer. Neat latex and latex filled with unmodified TiO2 nanoparticles were also prepared under the similar polymerization conditions as a control samples to have a worthwhile comparison. Results of TEM revealed that; the TiO2 nanoparticles are coated with the polymer nanolayer in a core-shell structure and uniform distribution of the nanoparticles in size of about 55 - 65 nm without any agglomerations, while latex filled with unmodified TiO2 nanoparticles showed the nanoparticles placed on the surface of the polymer particles. Thermal analysis including DSC and TGA was used to investigate Tg and thermal stability of the samples. DSC analysis demonstrated that Tg of the nanocomposites was increased as the content of the modified TiO2 nanoparticles was increased in compare with the neat polymer and that filled with unmodified TiO2 nanoparticles, while TGA results showed remarkably improved thermal stability due to the uniform dispersion of the non-agglomerated nanoparticles within the matrix of the polymer. Furthermore, the nanocomposite latexes showed improved hardness as the content of the encapsulated TiO2 nanoparticles increased in compare with the neat polymer and that filled with unmodified TiO2 nanoparticles indicating their superior mechanical properties. The prepared nanocomposite latexes were evaluated as binder in the waterborne paint. The paint films of the nanocomposite latexes showed a good opacity and have superior scrub resistance comparing to the control samples prepared under the similar polymerization conditions.

Keywords: Latex; Nanocomposite; TiO2 nanoparticles; Oleic acid; Miniemulsion polymerization.