Aqueous Dispersions from Biodegradable/Renewable Polymers

Interest in sustainable materials is opening up possibilities for biopolymers. Decreasing environmental strain is the concept of today, and the trend to replace oil-based products with biopolymers is being emphasized. However, production capacity of biopolymers is limited, melt processing can be challenging and barrier properties, especially against moisture, are not yet on a sufficient level for demanding packaging applications. Aqueous polymer dispersions are used for coating of paper/board to provide barrier properties or binding potential. Dispersions today are based on synthetic polymers poorly degraded in a biological environment. Dispersions would allow alternative application techniques for biopolymers, thin coatings and freedom for the formulation. Unfortunately, there are only few biopolymer dispersions available. This article presents techniques for preparing dispersions from biopolymers to be used in barrier and pigment coatings. Even though polymers or processes were not optimized, visually stable (non-settling) dispersions with relatively high solids content were prepared from certain grades of polylactide, polyhydroxyalkaonates and polycaprolactone. Nanostarch dispersions and a dispersion prepared from wood xylan were also included in the study. However, further work is needed to improve the film formation, the coating composition and thus the performance of the biopolymer dispersions.