Starch nanoparticle-based latexes for pressure-sensitive adhesive applications
May 20-25, 2018
Petroleum-based materials are the dominant feedstock for polymer production. Given the depletion of petroleum resources and associated environmental concerns, it is necessary to explore alternative renewable resources to produce polymeric materials.1,2 Experimental grade starch nanoparticles (SNPs) provided by EcoSynthetix Inc. (Burlington, ON) were used to partially replace non-renewable materials to yield SNP-containing latexes for pressure sensitive adhesive (PSA) applications. Emulsion polymerization was selected for the production of bio-based polymer latexes, because it uses water rather than organic solvents and therefore, is considered a more sustainable polymer production technology. Due to the hydrophilic nature of SNPs, they tend to reside in the water phase or, at best, at the particle-water interface. However, to maintain expected polymer performance, one would prefer to have the SNPs encapsulated in the particle by acrylic polymer, or to be at least partially covered by the acrylic polymer.3 To achieve this, SNPs were modified to encourage their incorporation into the latex particles. The modification of SNPs began with cross-linking using sodium trimetaphosphate (STMP), a non-toxic cross-linker, followed by attachment of vinyl groups to the SNP and subsequent polymerization of a moderately hydrophilic monomer (butyl vinyl ether) to the SNP. The modified SNPs were then incorporated in a semi-batch emulsion polymerization to produce stable SNP-based latexes for PSA applications. Stable latexes of up to 17 wt.% SNP loading and 42 wt.% solids were successfully produced with relatively low viscosities (97.5 to 131.5 mPa.s). Adhesive properties of films prepared using the SNP-containing latexes were investigated and compared with a basic acrylic formulation and blends of the basic acrylic formulation with SNPs. Increases in peel strength and tack, and decrease in shear strength for the SNP-containing latex films compared to the base acrylic formulation suggests that the modified SNPs are largely incorporated into the latex particles instead of mainly presenting in the aqueous phase.
(1) Zhang, Y.; Dubé, M. A. Green Emulsion Polymerization Technology. In SpringerLink; Advances in Polymer Science; Springer, Berlin, Heidelberg, 2017; pp 1–36.
(2) Belgacem, M. N.; Gandini, A. Monomers, Polymers and Composites from Renewable Resources; Elsevier: Oxford, UK, 2008; Vol. First.
(3) Benedek, I. Pressure-Sensitive Adhesives and Applications; Marcel Dekker Inc: Hoboken, 2004.
Yujie Zhang, Marc Dubé, and Michael Cunningham, "Starch nanoparticle-based latexes for pressure-sensitive adhesive applications" in "Polymer Reaction Engineering X (PRE 10)", John Tsavalas, University of New Hampshire, USA Fouad Teymour, Illinois Institute of Technology, USA Jeffrey Stubbs, HP Inc., USA Jose R. Leiza, University of the Basque Country, Spain Eds, ECI Symposium Series, (2018). https://dc.engconfintl.org/prex/11