The thermodynamics of liquid mixtures : an investigation into the low temperature bleaching of a cotton non- woven fabric using hydrogen peroxide.
Govender, Ursula Penelope.
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This thesis is presented in two parts. In part one, the excess molar volumes and the excess molar enthalpies have been determined for several binary systems at 298.15 K using an LKB flow microcalorimeter and/or a 2277 Thermal Activity Monitor and an Anton Paar Digital Densitometer. The excess molar volumes and excess molar enthalpies, V; and H; , have been determined for systems involving an alkanol (I-propanol, 2-propanol) mixed with a hydrocarbon (1hexene, I-heptene, l-octene, I-hexyne, I-heptyne, l-octyne). The results show trends relating to the degree of unsaturation of the hydrocarbon to the position of the hydroxyl group on the alkanol. The excess molar volumes and excess molar enthalpies, V; and H; of di-n-butylamine + diethyl ether or dipropyl ether or di-l-methylethyl ether or dibutyl ether or 1,1 dimethylethyl methyl ether or 1,1 dimethylpropyl methyl ether or tetrahydrofuran or tetrahydropyran or 1,4 dioxane have been measured over the whole composition range at the temperature 298.15 K in order to investigate di-n-butylamine - ether interactions. The V; values for each of the systems studied are negative with the exception of the mixtures of (di-n-butylamine + dibutyl ether or tetrahydrofuran or tetrahydropyran or 1,4 dioxane. The H; results over the whole mole fraction range are formed endothermically. Measurements were also made on mixtures involving (a cycloalkane + a pseudocycloalkane). The congruency theory was tested for the (cycloalkane + pseudo-cycloalkane) mixture. The cycloalkane mixtures studied here did not satisfy the null test of the congruency principle. In the second part of this thesis the main aim of the investigation was to apply ambient temperature hydrogen peroxide bleaching techniques to a novel non-woven fabric and to optimize the treatment conditions for this technique. Five cold-pad batch bleaching formulas were applied to the non-woven and the sample fabrics were analyzed for the following properties a) fluidity (measure of degree of degradation of the cotton fibre as a result of the bleaching process) b) wettability (absorbency) c) whiteness (using instrumental techniques) d) inherent fibre surface properties (SEM) A method was elucidated for the cold batch bleaching of the non-woven which produced a fabric with minimum fibre damage, an acceptable degree of whiteness and excellent absorbency properties. The treatment parameters of time (Xl), temperature(x2) and hydrogen peroxide concentration (x3) for this method were optimised using a multiple regression analysis for three variables and response surface plots.