Siloxane-based high solid acrylic latex

Scientists have developed a siloxane-based acrylic latex by mini-emulsion polymerisation for coatings with improved water resistance.

Latex in a beaker.
Samples with higher Young's modulus and higher terminal relaxation times result in improved blocking resistance.  Image source: 350543 - Pixabay (symbol image).

Water resistance of a coating is an important parameter in its protective nature. Therefore, developing a viable coating formulation for improved water resistance has significant research interest. In a new study, researchers have prepared an acrylic latex composed of poly (methyl methacrylate-co-butyl acrylate-co-acrylic acid) having high solid content (54–57 %) by mini-emulsion polymerisation. They synthesised a methacrylate-terminated tetrafunctional siloxane monomer (MTS) and used it at 0.5–4.0 wt% as a crosslinking comonomer in the acrylic emulsion formulation. The structural elucidation of MTS was performed by FT-IR, 1H & 13C NMR and ESI-MS analysis. The copolymer latexes were characterised in terms of their solid content, particle size and viscosity.

Improved water resistance

All the high solid latexes were stable for months without any coagulum. The analysis of microscopic, optical, thermal and mechanical properties of the air-dried cast films exhibited that the copolymers with MTS had rough surface morphology, high optical transparency (~98 % transmittance), and improved thermal properties and poor mechanical properties. In addition, the films showed improved water resistance as observed from the increased water contact angle from 43.0° (0 % MTS) to 64.2° (1 % MTS) and reduced water absorption from 50 % (0 % MTS) to 18.2 % (1 % MTS).

The study has been published in Progress in Organic Coatings, Volume 171, October 2022.

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