Molecular weight evaluation of depolymerized poly(ethylene terephthalate) using intrinsic viscosity

A series of poly(ethylene terephthalate) (PET) depolymerization experiments versus time was proceeded under optimal experimental conditions with microwave radiation, in which the temperature was 220°C, the pressure was 200 psi, the microwave power was 260 W, and the ratio of water to PET was 10 : 1. The relative viscosity of the feedstock PET grain and the residual solid products from depolymerization reaction at six different time, respectively, was measured in the solution of 60/40 (w/w) phenol/1,1,2,2‐tetrachloroethane. Then the approximate intrinsic viscosity was calculated from linear and exponential extrapolation of reduced viscosity. Molecular weights were calculated by Mark‐Houwink's equation, with values of K and α taken from the literatures. The results show that the molecular weights fell dramatically with increasing of reaction time, namely the number average molecular weight from 2.57 × 10 4 of the feedstock PET to 372 of the remained solid product at 240 min, and the weight average molecular weight of the samples fell from 3.89 × 10 4 to 408 correspondingly. The intrinsic viscosity decreased greatly with reaction, while the distribution of molecular weight turned to be steady. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008