Flexabrasion Applied to the Evaluation of the Photodegradation of Hair Fibers

Solar radiation is a significant source of damage to hair fibers. However, the instrumental measurement of the consequences of its interaction with hair fibers' constituents remains a challenge. In this work, the flexabrasion methodology was investigated as a potential tool to quantify the damage to mechanical hair properties caused by solar rays. The in vitro experiment developed for this study simulated four initial conditions of human hair samples, which subsequently underwent different periods of exposure to the radiation emitted by a Xenon arc lamp source. The statistical analysis of the results characterized the methodology's ability to evaluate the impact of solar radiation on the hair's mechanical resistance. More evident effects were observed on natural fibers subjected to exposures of up to 60 h and over, corresponding to about 1.5 h per day of sun exposure in Rio de Janeiro over five months. The results point to flexabrasion as an option to evaluate the photoprotection efficacy offered by hair-care products.