Degradation of Poly(butylene terephthalate) in Different Supercritical Alcohol Solvents Junhe Yang, 1 Jie Huang, 2 Minking K. Chyu, 3 Qing-Ming Wang, 3 Danliu Xiong, 2 Zibin Zhu 2 1 School of Materials Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China 2 School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China 3 Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15261 Received 23 March 2009; accepted 21 October 2009 DOI 10.1002/app.31649 Published online 14 January 2010 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Reactions were carried out in a batch auto- clave reactor. Poly(butylene terephthalate) (PBT) and dif- ferent alcohol solvents were used in the vessel. The reaction products were analyzed by infrared spectroscopy and gas chromatography/mass spectrometry. Alcoholysis of PBT occurred in supercritical methanol, ethanol, and propanol, and we obtained dimethyl terephthalate (DMT), diethyl terephthalate (DET), and dipropyl terephthalate (DPT), respectively. The conversion of PBT at different temperatures showed similar trends but different degrada- tion degrees. The reactivity for the alcoholysis of PBT in supercritical methanol was much higher than those in supercritical ethanol and propanol. DMT and 1,4-butane- diol obtained from the depolymerization of PBT in super- critical methanol reached 98.5 and 72.3%, respectively, at 583 K for 75 min. The yield of DET reached 76% for 75 min. V C 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 2269–2274, 2010 Key words: degradation; monomers; recycling INTRODUCTION The recovery of valuable products through the chem- ical recycling of polymers has been attracted attention in recent years for both environmental and economic reasons. There is a lot of ongoing research to find ef- ficient technologies to degrade waste plastics. 1 The exploration of supercritical fluids as solvents and as reaction media for polymer degradation has attracted particular interest over the past decade. 2–4 Because of their unique physical and chemical prop- erties, they have many advantages when they are used in polymer degradation, such as reaction in the homogeneous phase and high decomposition rates. 5,6 Tagaya et al. 7 investigated the degradation of polycarbonate (PC) in supercritical water with temperatures above 647 K. Chen et al. 8 observed that high yields of bisphenol A and dimethyl car- bonate were obtained with methanol to depolymer- ize PC. Huang et al. 9 studied the depolymerization of PC in ethanol. Sako and coworkers 10,11 studied the characteristics of the depolymerization of poly (ethylene terephthalate) (PET) in supercritical metha- nol using a high-pressure reactor. PET could convert into monomer completely at 603 K after 45 min. Kim et al. 12 investigated the mechanism of the alcoholysis of PET. Campanelli et al. 13 studied the depolymer- ization of PET in critical water at 523–553 K. Yang et al. 14 studied the methanolytic depolymerization of PET with supercritical methanol. Meng and co- workers 15,16 studied the alcoholysis kinetics of poly (butylene terephthalate) (PBT) in supercritical metha- nol and the effect of the reaction temperature and pressure on the decomposition of PBT. Shibata and Masuda 17 reported that the depolymerization of PBT at high temperature was an effective method for the quantitative recovery of dimethyl terephthalate (DMT) and 1,4-butanediol (BG). Huang and co- workers 18,19 studied the characteristics of the depoly- merization of PBT in supercritical methanol. However, the depolymerization of PBT in different alcohol solvents, such as ethanol and propanol, has not yet been reported. Thus, in this study, we exam- ined the degradation of PBT performed in supercriti- cal methanol, ethanol, and propanol in a batch-type autoclave reactor. The effects of the temperature and reaction time on the degradation degree, molecular weight, and yields of monomers were investigated. EXPERIMENTAL Material and solution The PBT used in the experiments was a commercial slice with a molar-average molecular weight (M n ) of Correspondence to: J. Huang (jie_h_64@hotmail.com). Contract grant sponsor: National Natural Science Foundation of the People’s Republic of China; contract grant number: 50773040. Journal of Applied Polymer Science, Vol. 116, 2269–2274 (2010) V C 2010 Wiley Periodicals, Inc.