Film formation of Alkali Soluble Resin (ASR) stabilized latexes

Abstract

Alkali soluble resin (ASR) stabilized latexes are commonly employed in the development of waterborne coatings with good mechanical properties. However, despite their widespread use, little is known about how the nature of the hydroplasticized, high Tg ASR influences the film formation process and how systems can be designed to minimize the minimum film formation temperature (MFFT). In this work we synthesize a series of ASRs and ASR stabilized latexes in order to explore how the ASR influences the drying and deformation processes occurring during film formation. It is shown the ASR absorbs water and serves to increase the effective volume fraction of polymer during drying. Despite often being considered as an aqueous solution, the ASR behaves more like a conventional colloidal polymer and its film formation behavior is dictated by the wet Tg of the ASR. In ASR/latex blends both the wet Tg of the ASR and the Tg of the main emulsion polymer affects the MFFT. It is shown that high Tg ASRs (Tg > 100 °C) can be easily used in formulations that have MFFT <20 °C. In addition, for latexes with high Tg (Tg > 60 °C), using correct design strategies, hydroplasticized ASRs can be employed to lower the MFFT to below ambient temperature. These insights should allow for the effective development of latex films with low MFFT but mechanical properties more comparable to their solvent based counterparts.