Details
Resources
Table of Contents
Related Links
Table of Contents
EFFECT OF EQUILIBRIUM PH ON THE STRUCTURE AND PROPERTIES OF BLEACH DAMAGED HUMAN HAIR FIBERS
Malinauskyte, E., Cornwell, P.A., Reay, L., Shaw, N., Petkov, J. (2020) Effect of equilibrium pH on the structure and properties of bleach damaged human hair fibers. Biopolymers. Submitted for publication
Hair proteins are significantly affected by environmental pH. This impact tends to increase with prior hair damage. To understand how pH affects bleached hair properties, we utilized a number of techniques allowing for the determination of hair thermal properties, swelling and water sorption, and dry and wet tensile properties. At pH 5, hair proteins had the best structural integrity, as determined by DSC and the highest tensile modulus. At pH 10, protein cross-linking density decreased, water content and hair cross-sectional diameter increased. These effects suggest that pH>10 is the best range to facilitate the penetration of actives. Alkaline treatment, when compared with pH 5, did not reduce intermediate filament conditions (evaluated via enthalpy measurement) nor mechanical property performance in the wet state. In contrast to alkaline treated hair, bleached hair equilibrated at pH 3 behaved very differently: it contained two different crosslink density zones, was the least stiff in dry and stiffest in wet conditions. Additionally, it absorbed less water and had lowest the diameter because of reduced water binding by protonated carboxyl groups. The pH 3-10 did not affect the mechanical strength of bleached hair in dry or wet conditions.