PU made from waste cooking oil suitable for lightweight structures

Researchers at the Indian Institute of Engineering Science and Technology (IIEST), Shibpur have developed and optimised a semi-rigid polyurethane foam derived from waste cooking oil (WCO), demonstrating a potential low-carbon alternative to petroleum-based foams for packaging applications. The study was published yesterday in the journal Waste and Biomass Validation.

The study reports the synthesis of waste-oil-derived polyurethane foam (WCODPU) using a Box–Behnken experimental design to optimise formulation parameters. The resulting foam achieved a density of 130.2 kg/m³, porosity of 89.15%, and a mean pore size of 483.6 μm, placing it in a range suitable for lightweight protective packaging.

Chemical and structural characterisation confirmed successful conversion of waste oil into a functional polyol and formation of a consistent polyurethane network. FTIR analysis verified urethane linkages, while SEM–EDS and XRD showed uniform pore morphology and elemental distribution throughout the foam structure.

The material also demonstrated improved durability and surface properties compared with polyurethane foams produced from edible oils. After 96 hours of UV ageing, the foam showed a controlled mass loss of 6.3%, alongside an increase in carbonyl index indicative of predictable degradation behaviour. Hydrophobic performance was significantly enhanced, with water uptake reduced to 15.9%, compared with 28.3% for edible-oil-based PU foam, and a higher contact angle of 84.5°.

Mechanical compression testing showed strong agreement with finite element simulations, with less than 10% deviation between experimental and modelled results. The authors validated the Ogden hyperelastic model for describing the foam’s mechanical response, supporting its use in predictive design.

A cradle-to-gate life-cycle assessment using the ReCiPe 2016 method calculated a carbon footprint of 19.1 kg CO₂-equivalent per kilogram of foam. The analysis found that environmental impacts were dominated by TDI production and process energy, while the contribution from waste cooking oil valorisation was minimal.

The researchers conclude that WCODPU offers a tunable, sustainable polyurethane foam platform with potential to replace fossil-based materials in packaging and other lightweight structural applications.

Photo: © Springer/IIEST

Waste and Biomass Valorization