Wool Shrinkproofing Studies

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Abstract
The influence of inorganic salts on reaction and clearing rates for treatment of wool in neutral solution with potassium permanganate has been studied. In addition to the manganese dioxide deposited on the fiber, reaction in distilled water produces a manganese dioxide sol, which makes qualitative observation of per manganate exhaustion difficult. No sol forms in salt solutions. Permanganate exhaustion is fastest at low salt concentration and slowest in zero and saturated salt solutions. Above 1 molar added salt concentration, the permanganate exhaustion rates are in the order: NaNO3 > NaCl > Na2SO4. The nature of the salt has no effect on exhaustion rates below 1 molar. The variation in reaction rate with salt concentration may be explained in terms of either fiber or solution properties. However, activation energy for the reaction is in the range 5,500 to 8,000 cal/mole, which suggests that the rate-controlling step is diffusion through surface solution rather than diffusion through the fiber. Rates of bisulfite clearing of manganese dioxide deposited on the fiber increase for permanganate treatments in increasing salt concentrations and reflect the depth of deposition of manganese dioxide. This is confirmed by optical microscopy. Treatment of wool with aqueous permanganate, followed by bisulfite clearing, results in a wool weight decrease, which is greatest for treatments in saturated salt solutions.