ScholarWorks@중앙대학교

초록

Background: Excessive heat from household styling devices denatures α-keratin, damages the cuticle, and degrades overall hair quality. Conventional blow-dryer temperatures often exceed 90°C, surpassing the safety threshold for keratin fibers. To determine whether combining focused airflow with rapid thermal cycling (peak temperatures ≤60°C) attenuates multiscale hair damage compared with continuous-heat drying. Methods: Human-hair tresses were assigned either to a focused-flow dryer operating in alternating cool/warm cycles or to a continuous-heat mode. Jet characteristics were quantified using planar particle-image velocimetry, and airflow temperatures were recorded using micro-thermocouples. Post-treatment analyses included scanning electron microscopy (cuticular surface roughness, Ra), single-fiber tensile testing, crosssectional densitometry (fiber compactness), and confocal Raman spectroscopy (α-helix/disulfide bond integrity). Results: Thermal cycling with focused airflow increased the central-core flow fraction from 37% to 64% and confined hair-surface peaks to 58°C-60°C. Alternating hot-cold drying reduced cuticlar surface roughness by approximately 7.3%, whereas continuous hat air drying increased roughness by 4.9%. Ultimate tensile strength was essentially preserved (–0.4%) under cycling but fell by 9.4% with uninterrupted heat (p = 0.003). Compactness loss was limited to 33% vs. 50%, and the S-S disulfide bond (~510 cm–1)/C-H bending vibration band (~720 cm–1) ratio decreased by only 11% (vs. 19% under continuous heat). Conclusion: Brief cooling intervals, when paired with a confined airflow, effectively prevented α-keratin denaturation and structural collapse. These findings support a clinically relevant approach to preserving hairfiber integrity during routine hair care and styling.

키워드