In Vitro Evaluation of Changes in Hair Fibers Subjected to Oxidation-Reductive Straighteners Associated with Dyeing

This study evaluated the effects of alkaline straightening using ammonium thioglycolate and amino methylpropanol, followed by permanent coloring, on hair fibers. Techniques such as FTIR, SEM, confocal microscopy, and fluorescence were used to assess changes in the hair fiber surface (cuticle), while DSC, TG, tensile tests, and diameter measurements evaluated changes in the cortex. The results indicated that both coloring and straightening induced changes in the cuticle and cortex, including oxidation of surface bands and denaturation of alpha-keratin chains. This comprehensive approach allowed for the investigation of physical-chemical changes in hair fibers subjected to these cosmetic procedures.