Comparative Studies on Chemical Recycling (Depolymerization) of Polyurethane Scrap Material

Author(s): Vishwanath S. Zope and Sumit V. Jadhav

Wide range of properties with respects to comfort, safety, designs and particularly in weight reduction, made the polyurethane (PU) foam, one of the most versatile material as a replacement to rubber. Superior material properties of PU finds wider range of application, in the industrial sectors such as carpets, automobile cushioning, refrigeration and insulations. This results in the generation of bulk of waste including pre and post consumer waste, which affects environment in many aspects of pollution. Present awareness of ecological aspects by public and also by politicians, researchers have been attracted to carry out the effective recycling of PU waste. Many techniques have been involved to carry out the recycling of PU scrap including physical (mechanical) recycling as well as chemical recycling. Amongst them, the route of chemical recycling is preferable, because of its ability to yield recycled products that can be used as an alternative to virgin raw material. In this communication, “Depolymerization” of PU scrap with varying solvent mixtures (Polyol + Catalyst) at different temperatures is reported. Depolymerization solvents were developed for glycolysis of PU foam. Measurement of hydroxyl value was found to be excellent to study the extent of depolymerization. PU foam used to study the depolymerization was found to have the molecular weight in the order of 106 . The dissolution time at 150°C in solvents polyethylene glycol (PEG) and diethylene glycol (DEG) were found to be 50 minutes, and 15 minutes, respectively, while it was 3 minutes for both solvents at 200°C. Energy of activation was found to be 52.82 KJ mole-1 and 66.78 KJ mole-1 , respectively for DEG and PEG. Similarly, the rate constants calculated were found to be 1.18 x 10-4 mole-1 and 3.39 x 10-5 mole-1 , respectively for DEG and PEG, which clearly indicates that glycolysis of PU foam proceeds at a faster rate in DEG.

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