Acrylic/Starch hybrid nanoparticles by emulsion polymerization for coating applications

CABRERA, SOFÍA F.; RONCO, LUDMILA I.; GUGLIOTTA, LUIS M.; MINARI, ROQUE J.

Buenos Aires

Congreso; 11th World Congress of Chemical Engineering (WCCE11); 2023

Asociación Argentina de Ingenieros Químicos (AAIQ)

Nowadays, the industry, technology, and science of polymers are very interested in developing new materials employing natural resources and, consequently, the total or partial replacement of petroleum-based monomers. In this context, starch is a great candidate to produce acrylic/biopolymer hybrid latexes, by limiting the use of synthetic monomers, and with potential application in adhesives and coatings.In this work, we studied the synthesis of acrylic/starch hybrid latexes, incorporating starch/zein bioparticles (BPs) as a seed in a semi-batch emulsion polymerization. The effect of acrylic formulation on the polymerization and the hybrid latex performance as water-based coating was investigated.BPs were synthesized by combining starch and zein following a nanoprecipitation method. Latexes were produced by semi-batch emulsion polymerization. Several BA/MMA formulations were studied: 90/10, 80/20, 70/30, 60/40, and 50/50. The mass ratio of BP/acrylic monomers was 20/80, with a theoretical solids content of around 20 %.All synthesized latexes presented a final monomer conversion above 90 %, with final average particle diameters (dp) ranged from 210 to 716 nm, which were influenced by the BA content. Lower dp were obtained from formulation with lower concentration of BA. In addition, hybrid particles with multi-lobular morphology were obtained for all the latexes, which contain a core of BPs surrounded by many lobules of acrylic copolymer. However, pure acrylic latex particles and free BPs were also observed.As was expected, the glass transition temperature (Tg) varied according the acrylic formulation, from -39.5 to 9.6, when MMA was increased from 10 to 50 %. All latexes presented a good film formation, with minimum film formation temperature (MFFT) below 3 °C. In addition, hybrid films showed a very good performance related to the blocking resistance, in spite of of their low Tg, due to the presence of some free BPs (with higher Tg) that reduce the tackiness of low Tg acrylic copolymer. Moreover, hybrid films showed a water swelling of around 40 %wt, lower than previous reported materials [1]. Most of the films presented a very good mechanical performance with high toughness, except when the highest BA concentration (BA/MMA = 90/10) was used. This might be because of phase segregation, as it was analysed by atomic force microscopy (AFM).In conclusion, the simultaneous incorporation of low Tg acrylic copolymer and starch/zein BPs (of high Tg) resulted in hybrid latexes which allow to overcame one of the biggest challenges in coating technology: to have at the same time a high blocking resistance and a low MFFT.