Polyurethanes (PU) have been used in various applications for decades such as foams, plastics, composites, films, sealants, coatings, inks, and adhesives. With increased global demand in sustainable and environmentally benign packaging, there is high demand to replace traditional petroleum-based materials with renewable, bio-derived sources. This research developed PU adhesives using plant oil extracts possessing naturally occurring hydroxyl functional groups towards development of a compostable, barrier multilayer flexible food packaging film. Intrinsic chemical functionality is beneficial to reduce cost and increase simplicity in comparison to traditional vegetable and plant oils that require chemical modification. Two oils containing different equivalents of hydroxyl functional fatty acids were used to understand the influence of a hydrocarbon side chain on adhesive physical properties and compostability of a multilayer film comprised of two commercially available compostable polymers. This study determined that the peel resistance possessed average peel strengths of 6-8 N relatively independent of oil composition. Furthermore, the adhesive glass transition temperatures were measured to be within the range of -25 to -44°C with higher concentrations of the hydrocarbon sidechain resulting in lower glass transition temperatures. The multilayer film was determined to have an average oxygen transmission rate of 14 cc/(m<sup>2</sup> day) and a water vapor transmission rate of 235 g/(m<sup>2</sup> day). These physical properties indicate their use in multilayer food packaging adhesive applications where isocyanate PU adhesives are still commonplace and requiring oxygen barrier properties. Understanding the PU adhesive network structure-property relationships will help develop the next generation of compostable bio-derived PU adhesives with additional sources of renewable feedstocks for food packaging applications. Additional research is in progress to further increase the barrier properties of this multilayer structure.

Sustainable plant oil-based adhesives for resealable multilayer food packaging films

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ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.