Spent coffee ground derived bio-polyol based flexible polyurethane foam with improved mechanical and sound absorption properties

Recently, bio-based polyols are gaining significant attention as sustainable alternatives to petroleum-based polyols for polyurethane (PU) foam production, promoting eco-friendly processing, renewable resource utilization, and reduced CO ₂ emissions during polyol synthesis. This report considered fabrication of flexible thermoset PU foam by partially replacing a conventional polyol with a recycled and bio-based polyol from different spent coffee grounds. To resemble properties like cream time, gel time, tack-free time, density, height, and other physical traits of the original foam, different experimental designs have been set up using the design of experiment (DOE) and statistical analysis considering different catalyst and surfactant contents. The effects of silicone surfactant and gelling catalyst with different contents on the physico-mechanical properties of modified with 10 parts by weight (pbw) recovered bio-polyol and unmodified PU foams were investigated. With the desire for higher compressive strength and lower heat shrinkage, the formulations of the bio-polyol-based foams are optimized with 0.75 pbw of catalyst and 1.2 pbw of surfactant amounts. Consequently, at optimized condition, the PU foam displays a compressive strength of 62 gf/cm ² and the lowest heat shrinkage rate (2.26%). Furthermore, the fabricated foam with unique cellular morphology shows a higher sound absorption coefficient at the lower and higher frequencies than the original foam, signifying its applicability in electric vehicles. Thus, owing to their impressive mechanical and acoustic characteristics, the developed bio-foams could serve as viable alternatives to traditional flexible PU foams for minimizing vibrations and noise pollution.