Waterborne Biopolymer Dispersions for Barrier Paper Coatings

Abstract

Demand for alternatives to synthetic, non-degradable, and single-use plastic packaging is continually increasing. Paper products are environmentally friendly and offer a potential solution, but typically do not meet performance demands without coating them with a polymeric film, usually polyolefins. Replacing conventional plastic coatings with biobased and biodegradable alternatives can substantially improve product sustainability. Furthermore, using water as a coating medium imparts further environmental and coatability advantages. In this thesis, the current state of waterborne coatings in industry is analyzed. Waterborne coatings are increasingly being used, containing conventional polyolefins, with the next step being to move towards more sustainable polymer options. Two different waterborne dispersions are formed using distinct biopolymers and stabilization mechanisms. First, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is dispersed in water via stabilization from the traditional surfactant sodium dodecyl sulfate (SDS). The dispersion demonstrates strong stability and coatability characteristics. Paper coated with the prepared waterborne PHBV dispersion exhibited strong barrier property performance relative to uncoated paper, with substantial improvements to water vapor permeability and grease resistance properties. A second study was performed in which a waterborne dispersion of cellulose acetate was formed using Pickering emulsion technique and cellulose nanocrystals. This dispersion exhibited similarly strong performance characteristics, with the coating again demonstrating strong barrier performance. Comparison to an industrially available product yielded competitive performance results as a food packaging container. Overall, the work demonstrates strong applicability of waterborne biopolymer dispersions as sustainable coating options.