Chemical Recycling of Flexible Polyurethane Foam Scraps Using Ricinoleic Acid as a Bio-Based Acidolysis and Glycolysis Agent

Annually, millions of tons of flexible polyurethane foam (PUF) are produced for a variety of applications. The large-scale production and disposal of PUF pose significant environmental challenges. Although reprocessing is employed as a strategy to mitigate PUF waste, flexible PUFs are frequently subjected to incineration or landfill disposal, thereby exacerbating environmental concerns. Acidolysis and glycolysis are recognized as effective industrial methods for recycling waste generated from PUF. This study presents a sustainable and cost-effective approach for the chemical recycling of flexible PUF waste. Ricinoleic acid, derived from castor oil, is utilized as a long-chain carboxylic acid to investigate the influence of dangling side chains and molecular weight on the acidolysis of PUF. The synthesized carboxylic acid functions as a bio-based, renewable, and environmentally friendly agent. Through the reaction with carboxylic acid, thermoset PUF is effectively converted into smaller molecules and oligomers that contain hydroxyl groups. The chemical structure of the recycled polyol was characterized using Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and gel permeation chromatography (GPC). The resulting recycled polyol (RP) demonstrates desirable industrial properties, including hydroxyl number, acid number, and viscosity, rendering it suitable for the production of flexible PUF. Moreover, the recycled polyol can replace up to 30% of the virgin polyol in the production of flexible PUF without compromising the mechanical properties of rigid polyurethane foams, thereby meeting commercial standards.