Influences of Specific Ions on the Physical and Chemical Structure of Human Hair

Abstract

Abstract The University of Manchester Katie Meredith Ann Hardie Ph. D. Materials Influences of Specific Ions on the Physical and Chemical Structure of Human Hair April 2018 This research project aims to investigate the effects of simple ions, such as hydrogen and hydroxide ions, on the chemical and physical characteristics of human hair. The external influence of substances which can penetrate hair fibres and alter their chemical structure and/or physical appearance is not only of purely fundamental scientific interest, but is commercially relevant, too. The hair care industry was valued at US$ 81.3 billion globally in 2015, and this is only forecasted to rise year on year (1). While research has been previously carried out on the effects of a variety of acids and bases on human hair and other related fibres, namely wool, this fundamental approach has not been taken before. While previous research focuses on auto-titration and soaking modified fibres with short immersion times, this research is focussed on the long term time-dependent pH-adjustment behaviour towards equilibrium of unmodified human hair. Probing these effects begins with the standardisation of commercial, Caucasian hair, untreated and bleached, in deionised water, then subsequent equilibration in hydrochloric acid (pH 1 – 7) and sodium hydroxide (pH 7 – 14) for a period of 24 hours, after which time it is assumed there will be no further change in pH. An experimental method was designed such that the pH-value of the solutions was measured at time points which would give roughly equidistant points on a logarithmic time scale. A deterministic kinetic model was developed and applied to the pH-change of solution and ion uptake of hair from solutions of known pH. Induced chemical changes to hair morphological components due to pH-environment/ion uptake were investigated using differential scanning calorimetry (DSC) and electrophoresis; the physical changes to the fibres were investigated using scanning electron microscopy (SEM).

Date of Award	1 Aug 2018
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Franz Wortmann (Supervisor) & Gabriele Wortmann (Supervisor)