Synthesis of Rigid Polyurethane Foams Incorporating Polyols from Chemical Recycling of Post-Industrial Waste Polyurethane Foams.

Izotz Amundarain,Rafael Miguel-Fernández,Sixto Arnaiz,Asier Asueta,Sara García-Fernández

doi:10.3390/polym14061157

Abstract

The preparation and characteristics of rigid polyurethane foams (RPUFs) synthesized from polyols obtained by glycolysis of post-industrial waste RPUFs have been studied. More precisely, waste rigid foams that have been chemically recycled by glycolysis in this work are industrially produced pieces for housing and bracket applications. The glycolysis products have been purified by vacuum distillation. The physicochemical properties of the polyols, such as hydroxyl value, acid value, average molecular weight (Mn) and viscosity have been analyzed. The chemical structure and thermal stability of the polyols have been studied by means of FTIR and TGA, respectively. Partial substitution of the commercial polyol (up to 15 wt.%) by the recycled polyols increases the reactivity of the RPUFs synthesis, according to short characteristic times during the foaming process along with more exothermic temperature profiles. Foams formulated with recycled polyols have a lower bulk density (88.3–96.9 kg m−3) and smaller cell sizes compared to a conventional reference RPUF. The addition of recycled polyols (up to 10 wt.%) into the formulation causes a slight decrease in compressive properties, whereas tensile strength and modulus values increase remarkably.

Highlights

Polyurethane (PU) is one of the most versatile polymers, offering a wide variety of commercial applications
The preparation and characteristics of rigid polyurethane foams (RPUFs) synthesized from polyols obtained by glycolysis of post-industrial waste RPUFs have been studied
Foams formulated with recycled polyols have a lower bulk density (88.3–96.9 kg m−3) and smaller cell sizes compared to a conventional reference RPUF

Summary

Introduction

Polyurethane (PU) is one of the most versatile polymers, offering a wide variety of commercial applications. Physical recycling processes do not modify the internal structure of the polymer; instead, the polymer residues are mechanically processed into flakes, granules or powder to be used in the production of new materials [6,7]. These physical processes can be successfully applied to thermoplastic polymers but are ineffective for most types of polyurethane due to their thermosetting nature. The glycolysis of RPUFs (Equation (1)) consists of treating the residues with a low molecular mass glycol, obtaining a homogeneous, single-phase product with low viscosity and high hydroxyl value that can be used as a partial substitute for commercial polyether polyols in the synthesis of new rigid foams [25,26]

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