Density, water, and swelling characteristics of cellular palm kernel oil bio-polyol modified polyurethane toward more sustainable growing media application

Developing a bio-based polyol polyurethane foam with the desired properties for use as growing media for green vertical walls could be beneficial in the quest to create a more sustainable urban living. In this work, palm kernel oil-based polyol (PKOP) was mixed with petroleum-based polyol (PP) at different ratios in synthesizing polyurethane foam. The impacts of PKOP/PP formulation on the density, cell morphology, water absorption, water retention, swelling behavior, and their chemical functional groups were evaluated. It was determined that replacing PP with low levels of PKOP could reduce the water absorption ability due to the introduction of hydrophobic plant-based fatty acids. On the contrary, polyurethane foam containing more than 30% PKOP has improved the water absorbing ability and retention properties. Fourier-transform infrared (FTIR) spectrum indicates that the synthesized foams are isocyanate-free and stable toward pH changes. The trial planting attempt was a success where the plants were grown from seeds using the synthesized foam media. It was proposed that 50% PKOP is most suitable for use as a growing media, based on its water absorbing and retention properties. The findings of this study highlight the potential for the use of bio-based polyol polyurethane foam for more sustainable growing media in urban gardens.