Role of 2-hydroxyethyl end group on the thermal degradation of poly(ethylene terephthalate) and reactive melt mixing of poly(ethylene terephthalate)/poly(ethylene naphthalate) blends

In an attempt to minimize the acetaldehyde formation at the processing temperatures (280-300 degrees C) and the outerinner transesterification reactions in the poly (ethylene terephthalate) (PET)poly(ethylene naphthalate) (PEN) melt-mixed blends, the hydroxyl chain ends of PET were capped using benzoyl chloride. The thermal characterization of the melt-mixed PETPEN blends at 300 degrees C, as well as that of the corresponding homopolymers, was performed. Degradations were carried out under dynamic heating and isothermal conditions in both flowing nitrogen and static air atmosphere. The initial decomposition temperatures (T-i) were determined to draw useful information about the overall thermal stability of the studied compounds. Also, the glass transition temperature (T-g) was determined by finding data, indicating that the end-capped copolymers showed a higher degradation stability compared to the unmodified PET and, when blended with PEN, seemed to be efficient in slowing the kinetic of transesterification leading to, for a finite time, the formation of block copolymers, as determined by H-1-NMR analysis. This is strong and direct evidence that the end-capping of the -OH chain ends influences the mechanism and the kinetic of transesterification. POLYM. ENG. SCI., 52:2498-2505, 2012. (C) 2012 Society of Plastics Engineers