Effect of epoxysilane oligomer on the stability and properties of Poly(Acrylic Acid) Solutions Used in Waterborne Paint Applications

Abstract

This study evaluates the effect of different amounts (0–6 wt%) of 3-glycidoxypropyl trimethoxysilane oligomer (ESO, CoatOSil MP 200) on the properties of partially neutralized poly(acrylic acid) (PAA) in aqueous solution at pH 5.6. The results revealed that ESO had a significant effect on the stability, viscosity, water absorption, glass transition temperature (Tg), and thermo properties of PAA. It has been demonstrated that it is possible to determine an optimal content of ESO, and higher ESO concentrations (> 2 wt%) led to increased viscosity, and the samples gelled within two months, making them unsuitable for aqueous PAA solutions and waterborne paints. The introduction of ESO enhanced thermal stability and residual mass, while FTIR analysis indicated a possible chemical reaction between epoxysilane and carboxyl groups of PAA. The viscosity increased over time for different ESO concentrations due to crosslinking and ester bond formation via epoxy ring-opening reactions. However, there is a concentration limit for the oligomeric silane used. At concentrations below 3 wt% of ESO, the mixture remained stable, whereas at 3 and 6 wt% the stability was compromised, leading to a significant rise in viscosity. Higher ESO content decreased the Tg and hardness of PAA, and an endothermic event was observed above 120 °C, evidencing chemical interactions between ESO and PAA. In summary, this study contributes to overcoming the challenges associated with PAA/ESO with a dispersing agent and provides additional insights into the gelation of waterborne paints and adhesives.