Formulation of Polyhydroxyalkanoate Aqueous Dispersions for Paperboard Food Packaging

Polyhydroxyalkanoates (PHAs) have been explored for use in paperboard food and beverage packaging as an environmentally friendly replacement to petroleum-based coatings like polyethylene. Paperboard coatings are primarily extrusion coated; however, extrusion coating requires the material to be processed above its melting point. The PHB homopolymer has a polymer melting transition peak around 175° C, which also coincides with the onset of thermal degradation, making it difficult to thermally process. Although tuning the PHA composition improves processability, the higher molecular weights inherent to PHAs are a drawback for extrusion coating. Thus, aqueous dispersion coatings have been an area of interest as an alternative. Herein, formulation components like surfactant systems, viscosity modifiers, and other additives are described and their use in formulating and optimizing stable dispersions are outlined. The functionality of the coating is assessed via barrier properties testing like water absorption, oil and grease resistance, cracking at the fold, and heat sealing ability. The results of these tests show competitive barrier performance when compared to polyethylene coated substrates currently used in the market and have led to the production of a completely biologically degradable and repulpable coated paperboard.