Relation between alkali solubility and tensile parameters in wool yarns subjected to acidic or oxidant treatments

摘要

Tensile parameters of fibres are related to the molecular weight of the polymer components. The shortening of the macromolecular chains produced by a given chemical attack can lead to more or less decrease in fibre tenacity. The molecular weight of the linear polymers can be determined by viscometry, this being the case of cellulosic, polyester and polyamide fibres. However, this simple technique cannot be applied to wool fibre as it is composed of polypeptide chains crosslinked with covalent bonds (disulphide links) which makes it insoluble in all solvents. However, the possible shortening of the polypeptide chains of wool can be evaluated relatively and indirectly by determining the end amine groups, whose increase means a decrease in the macromolecular chain length. The alkali solubility test of wool also allows detecting the shortening of the polypeptide chains. As It is well known, polymer solubility increases when its molecular weight decreases. In our case, an increase in wool alkali solubility means a chain shortening, always considering that other circumstances that also lead to alkali solubility increases are excluded.