Novel synthesis of flexible polyurethane foams with high biobased content derived from waste cooking oil

Sep 30, 2026

Production and characterization of open-cell flexible polyurethane foams with high bio-based content are investigated using waste cooking oil (WCO) as a precursor for polyols that replace fossil-based feedstocks. WCO is epoxidized to controlled degrees (66–94%) via heterogeneously catalyzed oxidation, then ring-opened with ethanol to obtain polyols with hydroxyl numbers of 132–177 mg KOH/g. These polyols are used in foam fabrication via confined expansion with a partially bio-based diisocyanate, tailored additives, water blowing, and an NCO/OH ratio of 0.9. Chemical, morphological, thermal, and mechanical analyses confirm successful foam formation, decreasing cell size with increasing hydroxyl number and dense, tunable structures (~80 wt.% bio-based; 82–87 kg/m3) and compression performance.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages16

Reading Time40 min

AccessFree to download

Introduction

Polyurethane foams: applications and production scale

Chemistry of polyurethane foams: structure and phase separation

Bio-based routes and need for renewable polyols

[www. nature.com/scientificreports](www. nature.com/scientificreports) OPEN Novel synthesis of flexible polyurethane foams with high biobased content derived from waste cooking oil Damiano Rossi1,2􀀍, Irene Anguillesi1,2, Miriam Cappello1,2􀀍, Maria Michela Dell’Anna3 & Maurizia Seggiani1,2 This study investigates the production and characterization of open-cell flexible polyurethane foams (PUFs) with high bio-based content, using waste cooking oil (WCO) as a precursor for polyols to replace conventional fossil-based polyols. WCO was epoxidized to varying degrees (66–94%) through heterogeneously catalyzed oxidation with Amberlite® IR 120, followed by ring-opening reactions with ethanol to synthesize polyols with hydroxyl numbers ranging from 132 to 177 mg KOH/g. These polyols were then used to produce PUFs through confined expansion, incorporating a partially bio-based diisocyanate, water as a blowing agent, and specifically tailored additives. An isocyanate-to-hydroxyl molar ratio (NCO/OH) of 0.9 was employed to achieve efficient foaming with different crosslinking densities. Comprehensive chemical, morphological, thermal, and mechanical analyses confirmed the successful production of open-cell flexible foams. The results indicated that cell size decreased with an increasing hydroxyl number of the polyol, corresponding to a higher crosslinking density. The foams exhibited an exceptionally high bio-based content of approximately 80 wt.%, densities ranging from 82 ± 1 to 87 ± 1 kg/m3, and compression force deflection (CFD) values at 50% deformation between 6.7 ± 0.5 and 56.5 ± 2.9 kPa. Higher hydroxyl numbers in the polyols resulted in increased CFD values, highlighting the effectiveness of hydroxyl number as a strategy to control foam cellular structure and mechanical properties. These findings demonstrate the potential ofWCO-derived polyols as a sustainable and efficient alternative to fossil-based raw materials in the production of flexible PUFs, offering a customizable approach for diverse applications. Keywords Waste cooking oil, Flexible polyurethanes foams, Bio-based polyols, Epoxidation, Recycling Polyurethanes (PUs) are a versatile class of macromolecular materials with an exceptional range of properties, making them widely employed in various sectors, including packaging, coatings, cushioning, insulation, footwear, construction, and automotive industries1. Global PU production reached nearly 26 million tons in 2022, and it is projected to grow to 32 million tons by 20302. Among these, polyurethane foams (PUFs) account for about two-thirds (15.6 million tons) of the total output and are classified as rigid or flexible foams based on their mechanical performance and core density3. Rigid foams are primarily used in structural and insulation applications owing to their high compressive strength, low thermal conductivity, and lightweight nature. In contrast, flexible foams, which exhibit viscoelastic behaviour, are commonly used in comfort and cushioning applications. PUs are copolymers characterized by urethane bonds (-NHCOO-) in their main chain, typically formed through the reaction of polyols with isocyanates. Additives, such as surfactants, catalysts, blowing and gelling agents, chain extenders, and foam stabilizers, are commonly required in foam manufacturing to achieve the desired properties. The structure of PUFs arises from the morphology and size distribution of soft and hard segments. Phase separation in polyurethanes refers to the thermodynamically driven microphase segregation of chemically incompatible soft and hard segments into distinct microdomains, resulting in a heterogeneous morphology that governs the mechanical, thermal, and viscoelastic properties of the material. In general, hard 1Dipartimento Di Ingegneria Civile Ed Industriale (DICI), Università Di Pisa, Largo L. Lazzarino 1, 56122 Pisa, Italy. 2Consorzio Interuniversitario Nazionale Per La Scienza E Tecnologia Dei Materiali (INS

FAQs

How is waste cooking oil converted into polyols in this study?

Waste cooking oil is epoxidized to different degrees (66–94%) using Amberlite IR 120, then ring-opened with ethanol to synthesize polyols with hydroxyl numbers from 132 to 177 mg KOH/g.

What foam formulation parameters control the foaming efficiency and crosslinking density?

Foams are produced by confined expansion using a partially bio-based diisocyanate, water as the blowing agent, specifically tailored additives, and an NCO/OH molar ratio of 0.9 to achieve efficient foaming at different crosslinking densities.

What trends were observed between polyol hydroxyl number and foam properties?

Increasing hydroxyl number leads to smaller cell size and higher compression force deflection (CFD) values at 50% deformation, showing that hydroxyl number effectively controls foam cellular structure and mechanical properties.

Sep 30, 2026

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