Low-Isocyanate Polyurethane Foams with Improved Stability and Compression Modulus Prepared from Biosourced and Landfill-Diverted Materials

Polyurethane foams are widely used in a variety of applications that impact everyday life, including single-use packaging and durable furniture. Currently, the industry depends primarily on petroleum-based reactants, such as polyols and isocyanates. Isocyanates are particularly troublesome due to their harmful effects on human health but are also crucial for achieving foam properties, such as rigidity. In this study, we demonstrate that cost-competitive, scalable, and more sustainable foams can be attained using biobased polyol substitutes along with landfill-diverted biofillers (rice hulls and coffee chaff) at a lower ratio of isocyanate. To avoid the common collapsing issue, we designed a prepolymerization step that can consistently produce high-quality foam with zero volume loss after expansion. The addition of biofiller increased the foam compression modulus drastically up to 400% at the same isocyanate concentration. Therefore, the incorporation of the biofiller provided a mechanism to enhance the mechanical properties without increasing the amount of isocyanates. Additionally, the reproducibility and foam properties can be further improved through grinding and sieving. The finer particles can be loaded at even higher levels without negatively impacting the mechanical properties. The same approach can be expanded to other types of biobased cellulosic biofillers. The results put forward a scalable, economical, and more sustainable route to improve foam performance while reducing isocyanate usage by incorporating biobased content.