Kao elucidates the mechanism of undulation that occurs specifically in the surface layer of hair

 Kao found that the undulations that occur on the surface of the hair disrupt the flow of the hair and impair the impression of the hair, and discovered that the undulations are deeply related to ultraviolet rays. Further investigation of the generation mechanism revealed that the bonds within the hair were cut under the influence of ultraviolet rays, and the cut parts recombined in a distorted state, a phenomenon similar to the mechanism of perms performed at beauty salons. I found it.

It has been confirmed that protecting hair from UV rays, which is one of the causes of waviness, is just as important as skin.

Irregular undulations in hair have been thought to be caused by natural habits and accumulation of damage due to hair coloring and heat. While there was little undulation on the inner side of the hair when the hair was turned up, there was a tendency for the surface layer of the hair to be significantly undulated. We tried to elucidate the factors and mechanisms of the swell that occurs in the

As a result of the evaluation based on the real life situation where the hair is exposed to sunlight when going out during the day and the time passes while the hair is distorted due to contact with the pillow when sleeping, it was found that sunlight irradiation alone does not change the shape of the hair. Although no significant change was observed, it was found that when the hair was held in a distorted state after irradiation, remarkable waviness occurred, and the longer the holding time, the stronger the waviness. On the other hand, since the generation of undulations was suppressed when ultraviolet rays were blocked from sunlight, it was found that ultraviolet rays and strain are major factors in the generation of undulations.

It has been reported that the disulfide (S-S) bonds that connect proteins like a ladder, which are present in many proteins that make up hair, are cleaved under the influence of ultraviolet rays. I didn't know. Therefore, in this study, we analyzed the change in the amount of S-S bonds during the process of waviness using Raman spectroscopy. As a result, it was found that the S-S bond was cleaved and decreased when irradiated with sunlight, followed by a rapid increase process and a gradual increase process. Furthermore, comparing the time of S-S recombination and the occurrence of waviness, the time when the waviness gradually became strong and the time when the recombination gradually progressed matched. In other words, it was clarified that this slow recombination corresponds to the S-S recombination between proteins and is associated with the generation of undulations.

Based on the above, it is thought that when the hair is placed in a distorted state after being exposed to ultraviolet rays, the cut S-S bonds are recombined in the distorted state, leading to the generation of waviness.