Kinetic Studies of Poly(ethylene terephthalate) Aminolysis Process without Catalyst

Chemical recycling of poly(ethylene terephthalate) bottle waste and production of value-added materials are the most appropriate ways in accordance with the principles of sustainable development and environmental protection. To design and build industrial-scale recycling plants, kinetic data and the relationship between reaction rate and material concentration and temperature and, most importantly, the degradation reaction constant are required.

Chemical recycling of poly(ethylene terephthalate) was performed using more than five times the stoichiometric amount of monoethanolamine and without any catalyst. The product was characterized using the conventional polymer characterization methods such as Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric (TGA), and the elemental analysis. The aminolysis reaction was carried out at three temperatures of 120, 140, and 160°C and the kinetics of the aminolysis reaction and its relationship with temperature were determined by sampling and weighing the residual or unreacted amount of PET at consecutive times.

Complete chemical degradation or aminolysis of poly(ethylene terephthalate) and its conversion to bis(hydroxyethyl) terephthalamide (BHETA) were performed in the presence of an excessive amount of monoethanolamine. The assumption of the first-order degree kinetics regime was used and its accuracy was confirmed by calculation error values. Experiments were performed at three temperatures to determine the rate of PET aminolysis reaction with respect to reaction temperature. Degradation of aminolysis under heating conditions using a jacket system for the reactor showed less activation energy than heating conditions with microwave radiation.