Bio-Synthetic Emulsion Polymer Latexes for Adhesive Applications

Abstract

Petroleum resources are the dominant feedstock used in polymer production, however, with the depletion of petroleum resources and the associated environmental concerns, it is necessary to explore alternative renewable resources to produce polymeric materials. Using experimental grade starch nanoparticles (SNPs) provided by EcoSynthetix Inc. (Burlington, ON) we have replaced a significant amount of non-renewable feedstock to yield SNP-containing latexes for adhesive applications. Due to the hydrophilic nature of SNPs, they tend to reside in the water phase or, at best, at the particle-water interface. Thus, to maintain expected polymer performance, we encapsulated SNPs in the acrylic polymer latex particles. To achieve this, SNPs were modified by increasing their cross-link density, then by functionalizing with a sugar-based monomer, and finally, by tuning their hydrophobicity. The modified SNPs were then incorporated in a semi-batch emulsion polymerization to produce stable SNP-based latexes. To understand the effect of each SNP modification procedure, a series of controlled experiments was conducted. Stable and low viscosity latexes with up to 45 wt.% SNPs and 55 wt.% solids have been produced. TEM and STEM images confirmed the presence of a core-shell morphology (SNP core/acrylic polymer shell), and mass balance calculations suggested a significant degree of encapsulation of the SNPs in the latex particles. Crosslinker and chain transfer agent were then used to produce SNP-based latexes with a variety of latex and adhesive properties by manipulating the acrylic shell polymer microstructure.