Chemical Reactions in Curing Treatment for Permanent Hair Straightening Using Thioglycolic and Dithioglycolic Acids

The study examined the chemical reactions in hair straightening using thioglycolic acid (TGA) and dithiodiglycolic acid (DTDG). It found that using TGA alone caused hair damage due to the formation of mixed disulfide groups, which were dependent on TGA concentration and converted to thiol groups during heat treatment. In contrast, the bicomponent system with TGA and DTDG linked only thiol groups to protein chains, even under high temperatures, indicating that DTDG acted as both a reduction-regulating and anti-damaging agent.