PFAS-free, zero-VOC soybean hull-based biopolymer for packaging, printing and coating applications

Abstract Transitioning from petroleum-based to biobased polymers is a global responsibility that allows the packaging, coating and printing industries to cut fossil fuel use, reduce pollution, and contribute to a healthier, more sustainable future. In pursuit of this goal, soybean hulls (SBH), an abundant agro-industrial byproduct, were valorized as renewable, per- and polyfluoroalkyl substances (PFAS) free biopolymer. A scalable acid-catalyzed thermochemical treatment yielded a water-soluble SBH powder, which was structurally and functionally characterized. The material exhibited zero volatile organic compound (VOC) emissions, high thermal stability up to 450 °C, and a glass transition temperature of 116 °C. FTIR confirmed polysaccharide- and lignin-derived functionalities that support hydrogen bonding, electrostatic interactions, and cohesive film formation. Rheological studies demonstrated shear-thinning behavior and viscosity of 240 cP at 25 °C. The 10 wt% solids content level for SBH was found to provide optimal balance between ease of processing, film strength, and barrier performance. When coated on recycled paper, and hardwood (HW) kraft pulp paper the oil and grease resistance fully improved from KIT #0 to #12. Water vapor transmission rate (WVTR) decreased by 9–15%, and tensile and burst index increased up to 40–50% compared to uncoated papers. In addition, the coated substrates exhibited favorable printability, characterized by uniform ink transfer, stable ink–substrate interaction, and consistent color reproduction, indicating compatibility with conventional printing processes such as flexography. The findings suggest that SBH could serve as a safe, non-toxic, versatile, and durable biopolymer for use in inks, coatings, paints and adhesives. Leveraging this low-value agricultural residue as a high-performance material may support circular economy strategies while helping reduce reliance on petroleum-based polymers.