Evaluation of Hair Humidity Resistance and Moisturization from Hair Elasticity

The study evaluated the humidity resistance and moisturization of hair by measuring hair elasticity (Young's modulus) and water regain in virgin dark brown and bleached hair fibers under different relative humidity (RH) conditions. It was found that hair water regain increased linearly with RH (40-85%), while hair elasticity decreased linearly with RH (50-80%). A Hair Humidity Resistance Factor (H(2)RF) was defined to assess the effectiveness of cosmetic treatments: R(2)HF > 1 indicated improved humidity resistance (anti-frizz), R(2)HF < 1 indicated enhanced water adsorption, and R(2)HF ≈ 1 indicated no significant effect. The method was used to evaluate several shampoo formulations, with Polyquaternium-70 shampoo showing the highest H(2)RF value and best anti-frizz performance. Results were consistent with Image Analysis findings.