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

Abstract

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.

Structural features of biobased composite foams revealed by X-ray tomography

“…This observation is supported by the residual strain data reported in the original study, where the control sample had only 3.1% permanent strain following 20 creep-recovery cycles. 3 Samples containing particles also experienced ligament fracture (Fig. 5c-e).…”

“…1,2 Recently, low-isocyanate polyurethane foams with improved stability and compression modulus have been successfully prepared from biosourced and landll-diverted materials. 3 As researchers strive to develop more sustainable alternatives to traditional petroleum-based foams, the changes in materials and processes will inevitably lead to unique structural properties. [4][5][6][7][8][9][10] In order to understand the structure-property relationships in these materials, it is critical to reveal the complex microstructure of the foam.…”

“…The variation of particle size significantly influences the foam properties. 3 Furthermore, the addition of rice hull particles not only provides mechanical reinforcements but can also alter the cellular structure of these foams. For example, foam structures may be influenced by rice hull particles acting as nucleation sites for pores or by particles hindering the expansion of pores during the foaming process.…”

“…Foam formulation nomenclature and properties of foam formulations as reported in the previous study 3. Compression modulus and creep-recovery test data shown were collected with samples oriented such that force was applied parallel to the foam rising direction…”

Satisfactory Tensile Strength and Strain of Recyclable Polyurethane with a Trimaleimide Structure for Thermal Self-Healing and Anticorrosive Coatings

“…TMI–DA is synthesized via the D–A reaction between TMI and furfuryl alcohol, and the bands at 3364 and 1772 cm –1 of TMI–DA are assigned to the corresponding −OH and CO bond in TMI–DA (Figure d). , Meanwhile, the characteristic band at 2270 cm –1 of MDI is the stretching vibration of −NCO groups, , and the bands at 2954 and 1720 cm –1 of PCL can be ascribed to corresponding −CH 2 and CO (Figure d). , During the reaction between MDI and PCL, the significant reduction of the characteristic band at 2270 cm –1 in MDI–PCL and the disappearance of the −OH band in PCL indicate the consumption of −NCO by the −OH group of PCL (Figure d) . In addition, the appearance of the −N–H band at 3320 cm –1 in MDI–PCL also confirms the formation of amide between −NCO and −OH (Figure d) .…”