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Gdańsk University of Technology

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

Polyurethane recycling is a topic of growing interest due to the increasing amount of polyurethanewaste. The main purpose of polyurethane feedstock recycling is to recover the starting polyol, a valuable material. In thiswork, amethod of polyurethane thermo-chemical recycling, glycerolysisbymeansof crude glycerine, is proposed. Themaineffort is focusedonthe employment of crude glycerine without purification from biodiesel production as a decomposing agent for polyurethane recycling. The influenceofpolyurethane-to-glycerinemass ratio (PU/GL)onchemical structurewas examined using Fourier transforminfrared (FTIR) and 1H NMR spectroscopies 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 1HNMRanalyses of the glycerolysates showed peaks similar to those of virgin polyol. FromGPC chromatogramsitwas concluded thatglycerolysates are amixture of compoundswith different molecularweights, such as recoveredpolyol, 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 1020gmol−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.

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