Computational insights into polyurethane recycling via glycolysis

Chemical degradation of plastics gives hope in terms of recycling, because after conducting the reactions that initiate chemical breakdown of the polymers, valuable starting materials can be obtained, which then can be used in later plastic production processes. There are 6 main types of chemical degradation methods which can be employed in polyurethane (PUR) waste management, namely alcoholysis, aminolysis, glycolysis, acidolysis, hydrolysis, and hydrogenation. According to the reaction environment for each chemical degradation process applicable for PUR waste management, glycolysis turns out to be one of the most optimal, and promising to use in industrial settings, because low pressure (1 atm), and moderately high temperature (190°C-200°C) is needed to carry it out with the help of catalysts which can be several types, such as base, acid, or organometallic ones. In the current research, the thermodynamics properties of glycolysis of model urethanes have been investigated using computational chemistry methods in the presence of base (1,4-diazabicyclo[2.2.2]octane (DABCO)) and organometallic (Sn(II) 2-ethylhexanoate) catalysts and compared to catalyst-free scenarios. The properly evaluated and verified computational methods could be used in the future to predict the feasibility of similar reactions, with different degrading agents or different catalysts, and by that, a lot of experimental time could be saved, and costs can be reduced.