Some Sorption Studies on Nylon and Wool

A review is made of the present knowledge of the subject of sorption in relation to textile fibres and it is pointed out that the exact role of the amino and amido groups of the polyamide or protein fibres in their behaviour with hydroxylic compounds, acids or acid dyes is not yet fully understood. The experiments were planned and the results are discussed to throw additional light on this behaviour. Sorption has been studied both from aqueous solution and from the vapour phase. The sorbates used were hydroxylic, phenolic or acidic compounds. The fibres used as sorbents included drawn, undrawn and powdered nylon, and untreated, acid treated, dyed and, deaminated wool, respectively. Sorption from aqueous solution The methods used for the study of sorption from aqueous solution are those commonly employed, with the difference that in this work, the material :sorbate ratio (and not the material: liquor ratio) was maintained constant. Such a procedure is more in keeping with the requirements of the law of mass action. The equilibrium concentration of the sorbate bath is expressed as 'relative concentration' which is defined as the actual concentration divided by the solubility at the temperature under study. It is shown how results so expressed are thus made easier of interpretation and more consistent. The following conclusions are drawn: (i) Resorcinol has a greater affinity towards nylon than phenol. (ii) In spite of its extremely low solubility in water, benzoic acid shows an appreciable sorption on nylon, whereas benzene sulphonic acid shows none. It is concluded that the former combines with nylon by hydrogen bonds at the -NH.CO- groups. (iii) A formula is derived for the isotherm of phenol on the assumption that the molecules of phenol behave as gas molecules and the solvent water is in effect an indifferent medium. The derivation of the formula then follows the kinetic considerations of Langmuir and the isotherm equation is similar to his equation. From a study of the isotherms at different temperatures, heats of reaction of phenol on drawn and undrawn nylon are calculated and it is shown how swelling and contraction complicate the interpretation. (iv) The data of rates of sorption have been utilised to calculate the activation energy of a sorbate on the fibre under investigation. This is done by drawing slopes to the rate curves at the zero point and thus calculating the velocity constants at different temperatures. The effect of variations in solubility with temperature are taken into account by dividing the velocity-constant by the solubility at the given temperature. Energies of activation thus calculated are given for phenol and benzoic acid. The activation energy of phenol on drawn nylon is about 18,000 cal/g. mol. whereas that on undrawn nylon is about 24,000 cal/g. mol. The energy of activation of benzoic acid on drawn nylon is about 25,000 cal/g. mol. (v) Isotherms of aqueous aniline on drawn nylon revealed an appreciable sorption of this compound by the fibre. It was later discovered that aniline from the vapour phase is not adsorbed by the fibre. It is suggested that aniline combines with nylon not directly but through a bridge of water molecules. Sorption from vapour phase McBain and Bakr's spring balance has been used for the study of sorption from the vapour phase. The cleaning of the fibre surface was done under high vacuum (10-4 mm.). Spirals of Pyrex glass have given very satisfactory service. (Abstract shortened by ProQuest.)