Recycling of off-grade pet via partial alcoholysis to synthesize functionalized pet oligomer nanocomposites

Off-grade poly(ethylene terephthalate) (PET) of industrial manufacturers was partially depolymerized using excess ethylene glycol in the presence of manganese acetate as a transesterification catalyst to synthesize PET oligomers. Influences of reaction time, Ethylene Glycol (EG)/PET molar ratio, catalyst concentrations, and particle size of off-grade PET on yield of partial glycolysis reaction were investigated based on BoxBehnken's design of experiment. Thermal analyses of glycolyzed products are examined by differential scanning calorimetry. The optimum samples were also well-characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy (1H-NMR and 13C-NMR). The optimal conditions to synthesize PET oligomer (melting point of about 180 degrees C) for a 120-min glycolysis reaction time were EG/PET molar ratio of 2 with no catalyst using granule-shaped PET. The same results were obtained for a 60-min glycolysis reaction time, including EG/PET molar ratio of 1 with the weight ratio (catalyst to PET) of 0.5% using average particle size of PET. Then, maleated PET as a compatibilizer for preparing PET nanocomposites was produced via reaction between maleic anhydride/phthalic anhydride composition and optimized PET oligomers based on central composite design of experiment. The combination of reaction time of 106 min and PhA/MA molar ratio of 0.85 gave the best results based on d-spacing and peak shift of nanocomposite samples. Hence, melt mixing of maleated PET with organoclay produced a good intercalation of layered silicate and good dispersion of clay in maleated PET matrix. Analysis of variance (ANOVA) was studied for both glycolyzed products and functionalized PET oligomers. POLYM. COMPOS., 2012. (c) 2012 Society of Plastics Engineers