Production of flexible foams derived from waste cooking oil

A preliminary paper published yesterday in the journal Scientific Reports outlines a novel method of making flexible polyurethane foams with bio-based content derived from waste cooking oil.

The paper is published with a disclaimer that it is an unedited version of the manuscript, and may contain errors, but it has been published to give early access to its findings.

The study explores the production and characterization of open-cell flexible PU foams with a high bio-based content. Waste cooking oil (WCO) serves as a precursor for polyols, replacing conventional fossil-based ones. WCO undergoes heterogeneously catalysed oxidation to varying degrees (66–94%) using Amberlite IR 120. This is followed by ring-opening reactions with ethanol to create polyols with hydroxyl numbers ranging from 132 to 177 mg KOH/g.

These polyols were then used to create PU foams through confined expansion. This involved a partially bio-based diisocyanate water as a blowing agent and carefully chosen additives. A specific isocyanate-to-hydroxyl molar ratio (NCO/OH) of 0.9 was used to achieve efficient foaming with various crosslinking densities. Detailed chemical, morphological thermal and mechanical analyses confirmed the successful production of open-cell flexible foams.

The results showed cell size decreased as the hydroxyl number of the polyol increased, leading to a higher crosslinking density. The foams contained an exceptionally high bio-based content of around 80% and had densities ranging from 82 ± 1 to 87 ± 1 kg/m³. Compression force deflection (CFD) values at 50% deformation ranged from 6.7 ± 0.5 to 56.5 ± 2.9 kPa. Higher hydroxyl numbers in the polyols resulted in increased CFD values, demonstrating the effectiveness of hydroxyl number as a strategy for controlling foam cellular structure and mechanical properties.

The research has been carried out by researchers in Italy: Damiano Rossi, Irene Anguillesi, Miriam Cappello, Maurizia Seggiani and Maria Michela Dell’Anna, who are affiliated to the University of Pisa, INSTM Florence, and Polytechnic of Bari. The researchers give acknowledgements to Covestro, for supplying the project with Desmodur CQ N7300, Evonik Industries for supplying foaming agents, and Dr Rüdiger Sehling of Netzch for providing technical support on performing DMA analysis on the waste-oil-derived foams.

The research was a recipient of funding from the European Union Next Generation EU National Sustainable Mobility Centre.

Photo by Fulvio Ciccolo on Unsplash

Scientific Reports