High Biobased Content Coatings and Pressure Sensitive Adhesives through Blends of Natural Rubber Latex and Tailored Acrylic Dispersions

Abstract

Natural rubber latex is a widely available, biobased polymer dispersion but the mechanical properties limit its use in a number of common applications of colloidal polymers, such as coatings and adhesives. In this work, the synthesis of a series of biobased acrylic latexes is discussed, which are capable of manipulating the mechanical properties of films cast from natural rubber latex in order to expand the range of potential applications. On the one hand, a series of isobornyl acrylate-rich, hydroplasticizable latexes containing methacrylic acid are synthesized. Blends of the neutralized form of these acrylic latexes with natural rubber latex lead to a phase-separated film structure containing glassy domains of the poly(isobornyl acrylate)-rich polymer and softer domains of the natural rubber latex. This film structure results in an increase of the Young's modulus of several orders of magnitude, which makes them of interest for coatings. On the other hand, when similar non-hydroplasticizable poly(isobornyl acrylate) latexes are synthesized but with much lower molar mass, the relatively high T_g acrylic component and the low T_g natural rubber latex are miscible, leading to a tackified system that displayed reasonable adhesive properties. These results demonstrate a route to coatings and adhesives with high biobased content.