The Study On Relationship Between Hair Damage And Performance And The Impact Of Water On Hair Damages

In our daily life, many factors including the environment, hairdressing and dailynursing can cause damages to hairs. The influence of different damage way on hairperformance and handling is the issue of concern. This paper aims to establish avariety of damage models, and to study the physical and chemical properties of thehair before and after damage. It may help us fully understand the mechanism of hairdamage as well as providing a more powerful theoretical basis for damage repair anddaily protection of hair.Firstly, the relationship between hair’s performance change and its appearanceand handling was studied. A series of methods were established to systematicallycharacterizing the hair’s chemical and structural properties before and after change.The change of hair’s surface morphology, tensile strength, elongation, surfacehydrophilicity, friction coefficient and surface chemistry before and after damagewere tested using scanning electron microscopy, atomic force microscopy, fiberstrength tester, contact angle measurement, fiber friction tester, infrared spectroscopyand so on. The above physical and chemical properties were associated with the lookand feel of the hair to guide the follow-up work.Common injury ways in daily life were simulated to explore the hairperformance before and after damage, and the different damage mechanisms werestudied. Two types of damage modes including physical damage treatment (combingand abrasion) and chemical damage treatment (perm, UV, heat stretching) werecarried out. The results showed that: after physical damage, the structural integrity ofcuticular layer of the hair sample was destroyed, then the coefficient of frictionincreased. The damaged hair samples were more sensitive to moisture changecompared with original ones, and severe combing damage would affect hair fiberstrength. As for the chemical damage progress: hair cuticular layer was destroyed, and scales became curled or even fell off, then the friction coefficient increased. Changesof hair surface Zeta potential led to the enhancement of its hydrophilic. Hair fiber’smechanical tensile properties declined, which may be caused by the structure damageof the substance alpha keratin fiber and decrease of its crystallinity. Differentialscanning calorimetry examined the thermal decomposition characteristics of the hair.The extent of hair damage can be determined through the change of hair structuralmaterial-alpha helix material of alpha keratin. Fluorescence spectrometry andcoomassie brilliant blue method evaluated the extent of the damage hair respectivelyby determining the content of protein and cysteine. These above three methods cannot only reveal qualitative changes in the structure and composition of hair samplesafter chemical injury treatment, but also quantitative evaluate the extent of hairdamage.This paper further explored the impact of the presence of moisture to the hairdamage, because hair care processes are inseparable from the water environment andthe water is one of the important components of the hair. Compared dry and wet hairfiber in their performance, the results showed that wet hair fiber’s mechanical tensileproperties is worse, the surface roughness and friction coefficient is larger. The paperalso explored the role of water in the damage process, compared the change of hairperformance after different damage processing under dry and wet state. The resultsshowed that: in combing process, the moisture increased hair surface roughness byincreasing the damage degree; in Ultraviolet aging process, the synergy betweenphotodegradation and water expansion led to the aggravated damage; in heatstretching process, the existence of moisture alleviated the damage of hair.