Abstract: The water vapourpermeability and wet rub fastness of leathers finished with acrylic polymer based resin binder was carried out using the popular water vapour permeability cup method and the VESLIC test method respectively. Five formulations (125 g, 150 g, 175 g, 200 g and 250 g) of the binder which was the factor varied in this experiment, was prepared and then was applied on the originally retanned leathers from which five samples was generated. The effect of the finish formulations on water vapour permeability and wet rub fastness of the originally retanned leathers were investigated. Water vapour permeability test was also carried out for the unfinished (originally retanned) leathers as control samples. The results indicated that the water vapour permeability of the finished leather samples was significantly lower when compared to that of the unfinished (control) leather samples. However, for the finished leather samples, water vapour permeability increases as the quantity of the binder varied in this experiment was increased. The result of the VESLIC test indicated the resistance of the finished leather samples improves as the quantity of the binder varied in this experiment was increased. The overall results showed that the formulations containing the 200 g and 250 g of the acrylic polymer binder are good for leather finishing applications where suitable water vapour permeability and excellent rub fastness are both required.Abstract: The water vapourpermeability and wet rub fastness of leathers finished with acrylic polymer based resin binder was carried out using the popular water vapour permeability cup method and the VESLIC test method respectively. Five formulations (125 g, 150 g, 175 g, 200 g and 250 g) of the binder which was the factor varied in this experiment, was prep...Show More
Abstract: The kinetics of oxidations of caffeine by permanganate ion in both perchloric and sulfuric acids solutions have been investigated spectrophotometrically at a constant ionic strength of 1.0 mol dm-3 and at 25°C. In both acids, the reaction-time curves were obtained with a sigmoid profile suggesting an autocatalytic effect caused by Mn(II) ions formed as a reaction product. Both catalytic and non-catalytic processes were determined to be first order with respect to the permanganate ion and caffeine concentrations, whereas the orders with respect to [H+] and [Mn(II)] were found to be less than unity. Variation of either ionic strength or dielectric constant of the medium had no significant effect on the oxidation rates. Spectroscopic studies and Michaelis-Menten plots showed no evidence for the formation of intermediate complexes in both acids suggesting that the reactions point towards the outer-sphere pathway. The reactions mechanism adequately describing the kinetic results was proposed. In both acids, the main oxidation products of caffeine were identified as 1,3,7-trimethyluric acid. Under comparable experimental conditions, the oxidation rate of caffeine in perchloric acid was slightly higher than that in sulfuric acid. The constants involved in the different steps of the reactions mechanism have been evaluated. With admiration to the rate-limiting step of these reactions, the activation parameters have been evaluated and discussed.Abstract: The kinetics of oxidations of caffeine by permanganate ion in both perchloric and sulfuric acids solutions have been investigated spectrophotometrically at a constant ionic strength of 1.0 mol dm-3 and at 25°C. In both acids, the reaction-time curves were obtained with a sigmoid profile suggesting an autocatalytic effect caused by Mn(II) ions forme...Show More
