Case Study 616 Surface Properties of Human Hair by iGC and DVS
This case study reports a laboratory investigation of the surface energetic heterogeneity and water sorption behavior of three types of human scalp hair—undamaged caucasian virgin, thermally damaged (70 °C), and chemically bleached. Using an Inverse Gas Chromatography Surface Energy Analyzer (iGC SEA), the authors measured dispersive (γS^D) and specific acid‑base (γS^AB) surface energy distributions by probing the hair with alkanes and polar molecules, applying the Dorris‑Gray method for dispersive components and the van Oss/Della Volpe approach for acid‑base contributions. Results show that both heat and bleaching increase the mean γS^D (from 32.87 mJ m⁻² in virgin hair to 38.53 mJ m⁻² in heat‑treated and 36.25 mJ m⁻² in bleached hair) and γS^AB (1.86 → 2.43 → 3.88 mJ m⁻²), indicating a higher density of high‑energy polar sites, likely due to removal of the low‑energy lipid cuticle layer. Wettability, expressed as γS^AB/γS^T, rises from ~0.053 (virgin) to ~0.098 (bleached). Dynamic Vapour Sorption (DVS) measurements at 25 °C (0–95 % RH in 10 % steps) reveal that bleached hair absorbs significantly more moisture above 60 % RH, while thermally damaged hair exhibits pronounced sorption/desorption hysteresis, suggesting deeper moisture penetration and restricted diffusion. The study concludes that iGC SEA combined with DVS provides a robust platform for quantifying how cosmetic treatments alter hair surface energetics and moisture handling, with implications for formulation design in personal care products.
Topics
Hair Damage Mechanisms and Their Impact on Surface Chemistry
Overview of how bleaching, heat, and oxidative processes alter hair's internal structure and surface composition, including the role of amino acids and lipid layers.
iGC SEA Experimental Design for Measuring Dispersive and Acid‑Base Surface Energies of Hair
Details of the iGC SEA setup: 30 cm column, 4 mm ID, helium carrier, pre‑conditioning, probe selection (alkanes, polar molecules), Dorris‑Gray dispersive analysis, polarisation approach, van Oss/Della Volpe acid‑base calculations.
DVS Protocol for Assessing Moisture Sorption Isotherms of Treated Hair Fibers
Description of the Dynamic Vapour Sorption experiment: 0–95 % RH in 10 % increments at 25 °C, helium carrier, methane dead‑volume correction, pre‑conditioning, mass change tracking.
Surface Energy Heterogeneity Findings: Increased Dispersive and Acid‑Base Energies in Damaged Hair
Presentation of quantitative results showing higher mean γ_S^D and γ_S^AB for heat‑treated and bleached hair, interpretation that removal of the lipid cuticle creates more high‑energy sites.
Moisture Uptake and Hysteresis: DVS Insights into Bleached vs Thermally Treated Hair
Comparison of DVS sorption isotherms: bleached hair shows greater moisture uptake above 60 % RH; thermally damaged hair exhibits larger sorption/desorption hysteresis, indicating deeper moisture penetration and diffusion constraints.