ABSTRACT:In this study, emeraldine base (EB)-form polyaniline (PANI) powder was chemically prepared in 1M HNO 3 aqueous solution. The thermal characteristics and chemical structures of this powder were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). A polarizing optical microscope was also used to examine the crystalline morphology of this sample. The results indicated that the EB-form PANI powder had a discernible moisture content. Moreover, in the first run of DSC thermal analysis, the exothermic peak at 170 -340°C was due to the crosslinking reaction occurring among the EB-form PANI molecular chains. FTIR and XRD examinations further confirmed the chemical crosslinking reaction during thermal treatment. TGA results illustrated that there were two major stages for weight loss of the EB-form PANI powder sample. The first weight loss, at the lower temperature, resulted from the evaporation of moisture. The second weight loss, at the higher temperature, was due to the chemical structure degradation of the sample. The degradation temperature of the EB-form PANI powder was around 420 -450°C. The degradation temperature of emeraldine salt (ES)-form PANI powder was lower (around 360 -410°C) than that of the EB form (around 420 -450°C). From the TGA results, I roughly estimated that 2.74 aniline repeat units, on average, were doped with 1 HNO 3 molecule in the ES-form PANI. I found a single crystalline morphology of EB-form PANI, mostly like a conifer leaf. More complex, multilayered dendritic structures were also found.
ABSTRACT:The glycolysis of recycled poly(ethylene terephthalate) flakes by ethylene glycol (EG) is investigated. Bis-2-hydroxyethyl terephthalate (BHET) and oligomers are predominately glycolysis products. The influences of glycolysis temperature, glycolysis time, and the amount of catalyst (cobalt acetate) are illustrated. The BHET, dimer, and oligomers are predominately glycolysis products. The optimum glycolysis temperature is found to be 190°C. If a 190°C glycolysis temperature, 1.5-h glycolysis time, and 0.002 mol glycolysis catalyst (cobalt acetate) are used, the glycolysis conversion is almost 100%. The glycolysis conversion rate increases significantly with the glycolysis temperature, glycolysis time, and the amount of cobalt acetate. Thermal analyses of glycolysis products are examined by differential scanning calorimetry. In addition, the chemical structures of glycolysis products are also determined by a Fourier transform IR spectrophotometer.
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