Single‐phase product obtained via crude glycerine depolymerisation of polyurethane elastomer: structure characterisation and rheological behaviour

Abstract

AbstractPolyurethane recycling is a topic of growing interest due to the increasing amount of polyurethane waste. The main purpose of polyurethane feedstock recycling is to recover the starting polyol, a valuable material. In this work, a method of polyurethane thermo‐chemical recycling, glycerolysis by means of crude glycerine, is proposed. The main effort is focused on the employment of crude glycerine without purification from biodiesel production as a decomposing agent for polyurethane recycling. The influence of polyurethane‐to‐glycerine mass ratio (PU/GL) on chemical structure was examined using Fourier Transform Infrared (FTIR) and Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy and Gel Permeation Chromatography (GPC). Glass transition temperature (Tg) and thermal properties using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and also rheology were analysed. FTIR and 1H NMR analyses of the glycerolysates showed peaks similar to those of virgin polyol. From GPC chromatograms it was concluded that glycerolysates are a mixture of compounds with different molecular weights, such as recovered polyol, urethane oligomers or carbamates. Glycerolysates indicated Tg in the range from −65 to −60 °C and, for high PU/GL ratio, a second Tg appeared. Thermal stability of glycerolysates increased with increasing PU/GL ratio. The molecular weight of glycerolysates ranged from 700 to 1020 g mol−1 depending on PU/GL mass ratio. The semi‐products were defined as non‐Newtonian fluids, where viscosity depended on the shear rate. Crude glycerine, derived from biodiesel production, was successfully used in polyurethane decomposition, resulting in valuable semi‐products. © 2016 Society of Chemical Industry