Prevention of Hair Heat Damage via Thermoresponsive Organic Silicon-Modified Keratin

Heat damage is a common phenomenon that often occurs when drying and straightening hair. After heat damage, the hydrophobic barrier on the hair's surface becomes disrupted, thereby altering the hair's hydrophilicity. Meanwhile, during the process of heat damage, the rupture of the hair's cuticles causes the hair to become dry and rough, with a decrease in gloss and a decline in mechanical properties. This study utilized epoxy silane and hydrolyzed wool keratin to synthesize a thermally responsive organic silicon-modified keratin (OSK) to prevent hair from heat damage. OSK was synthesized from epoxy silane and hydrolyzed keratin, with yield determined by quantifying free amino groups. Its hair-care performance was evaluated through assessments of hair surface morphology, mechanical properties, and optical gloss, and by combing test and contact angle measurements. Mechanisms underlying surface hydrophobicity and hair scale protection were investigated using FTIR, XPS, and DSC. Specific performance parameters were evaluated using a single-fiber strength tester and a multifunctional hair-testing instrument. FTIR confirmed successful covalent grafting, with synthesis optimized to a 90.67% yield. OSK forms a protective film on hair surfaces, verified by SEM, XPS, and TEM, restoring damaged hair hydrophobicity to a 117° contact angle and enhancing thermal protection to 136° upon heating. Beyond hydrophobic-barrier restoration, OSK improved hair gloss by 30.26% and reduced frizz by 39.33%, while restoring the key performance of virgin hair. It also provides exceptional water-repellency protection and sensory enhancement. Under thermal stress, the protective film mechanically increased tensile strength by 6.58% and yield zone tensile force by 4.65%. This article demonstrates that OSK is an effective heat-sensitive agent. When damaged by heat sources such as hair dryers, it will form a protective film on the surface of the hair, thereby protecting the surface properties of the hair.