Single phase chemical recycling and refoaming with recycled polyol of rigid PUR/PIR insulation foams

Abstract

The increasing need for sustainable solutions to manage end-of-life polyurethane materials has drawn attention to chemical recycling processes, particularly glycolysis, as a promising approach for recovering valuable resources from rigid polyisocyanurate (PIR) foams. This thesis investigates the optimisation of PIR chemical recycling through a systematic study of solvolysis conditions using catalytic and deaminating agents, followed by refoaming tests using recycled polyols.

Experimental work was carried out on three industrially produced PIR foams (AMC01, Purinova, Advandcore) and one industrial PUR foam (Trier), assessing the influence of catalyst dosage and deaminating agent concentration on multiple key polyol parameters. In addition to viscosity and the formation of secondary degradation products such as methylene dianiline (MDA), particular attention was paid to hydroxyl value (OHV) and acid value (AV), in order to comprehensively characterise the polyol’s reactivity and chemical quality. Based on these variables, a formulation compromise was established to ensure acceptable viscosity, limited MDA content, and favourable OHV and AV profiles.

To support formulation decisions and accelerate optimisation, a predictive tool was developed in Excel using macros programmed in Visual Basic for Applications (VBA). This tool integrates experimental data with statistical models, including linear regression and Random Forest algorithms, to estimate polyol viscosity and recommend optimal formulations, including for polyol mixtures obtained from various foam combinations.

Refoaming tests using a mixture of 30% recycled polyols and 70% virgin polyols, corresponding to polyols currently used in industrial formulations, demonstrated satisfactory performance in terms of thermal conductivity, dimensional stability, compressive strength, and flame retardancy. These results confirm the technical feasibility of incorporating recycled PIR polyols into new rigid foam formulations. A pilot-scale campaign is planned to validate the scalability of the process, and future work will focus on refining predictive models and assessing environmental benefits through life-cycle analysis.

This work highlights the potential of optimised PIR rigid foams glycolysis as a viable route for the circular valorisation of rigid foams, contributing to more sustainable insulation materials and industrial practices.