Measurement of Hair Thermal Diffusivity with Infrared Microscopy Enhanced Ångström's Method
18 Pages Posted: 10 Oct 2019 First Look: Under Review
While heat acts as an essential component of various hair care processes, the thermal properties of hair are little studied and these properties dictate how heat is spread and stored in hair. Here, the infrared microscopy enhanced Ångström's method is introduced for accurate measurement of thermal diffusivity of hair. Four factors that could influence the thermal diffusivity were statistically tested: (1) hair type, (2) the specific fiber from the same hair type, (3) the specific locations along the same hair fiber (i.e., near the root vs. near the tip), and (4) the humidity level at which the hair is conditioned. The results indicate that the average thermal diffusivity of hair across the types measured is 0.148 mm2/s, which is in good agreement with the published data. Also, hair type, fiber, and location had no statistically significant impact on the thermal diffusivity, while increasing humidity level significantly reduced the thermal diffusivity. This seems to be due to the higher specific heat capacity of water than air, which dominates the heat transport and lowers the effective thermal diffusivity of hair which contains both.
Keywords: hair, thermal diffusivity, infrared microscopy, Ångström's method, thermal characterization
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