Kinetics and thermodynamics of hydrolytic depolymerization of polyurethane foam at higher temperature and pressure

Polyurethane (PU) foam was hydrolytically depolymerized in 0.5 L capacity high-pressure autoclave equipped with magnetic stirrer at 100, 130, 150, 170, 200, and 220degreesC and at 15, 51, 80, 153, 230, and 405 psi pressures. The percentage conversion of PU foam to polyamines and polyols on the basis of amine value and hydroxyl value was investigated and found to be 85 and 90%, respectively, at 200degreesC and at 230 psi pressure for 30 min reaction time. The velocity constants under these conditions recorded on the basis of amine value and hydroxyl value were 6.238 x 10(-2) and 6.359 x 10(-2) min(-1), respectively, which was found to be pseudo-first-order. The energies of activation on the basis of amine and hydroxyl value were recorded as 27.62 kJ/g mol and 28.14 kJ/g mol, respectively, while frequency factors on the basis of amine and hydroxyl value were recorded as 70.29 and 81.44 min(-1), respectively, for the 30-min reaction time at 200degreesC temperature and 230 psi pressure. The values enthalpy of activation at 130, 150, 170, 200, and 220degreesC, calculated on the basis of amine values, were 24.38, 24.22, 24.06, 23.80, and 23.64 kJ/g mol and on the basis of hydroxyl values were 25.31, 25.15, 24.98, 24.73, and 29.57 kJ/g mol, respectively.