Publications by authors named "F-J Wortmann"

The appearance of hair is a crucial factor of human well-being. Besides hair color and shine, the dynamic movement characteristics have a great impact on a youthful look, which is desirable at all ages. However, the hair follicle is subject to biochemical changes which tend to become obvious in the mid-30s by the appearance of the first nonpigmented "gray" hairs.

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Torsional analysis of single human hairs is especially suited to determine the properties of the cuticle and its changes through cosmetic processing. The two primary parameters, which are obtained by free torsional oscillation using the torsional pendulum method, are storage (') and loss modulus (″). Based on previous work on ', the current investigation focuses on ″.

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Through measurements of three different hair samples (virgin and treated) by the torsional pendulum method (22°C, 22% RH) a systematic decrease of the torsional storage modulus G' with increasing fiber diameter, i.e., polar moment of inertia, is observed.

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The expert working group 'Hair Care Products' of the DGK currently conducts a wide study to contribute to the understanding of how single hair fibre and hair collective properties contribute towards hair 'handle' and 'feel'. During the first stage of this study four hair types were selected from a large group of individual European hair braids, according to either similar or widely different panel ratings for handle. Against the background of the panel test and the state of the literature the working group readily identified the bending properties of single fibres interacting in the tress as a fibre collective and fibre friction as being of central relevance for hair 'handle' and 'feel'.

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Article Synopsis
  • The glass transition temperature (T(g)) of human hair is found to be 144 degrees C, lower than wool's 174 degrees C, due to a higher content of hydrophobic proteins acting as internal plasticizers.
  • The relationship between water content and glass transition in hair follows the Fox equation, indicating a homogeneous distribution of water within the hair's protein structure.
  • Thermal denaturation of hair showed no change in water content or T(g), reinforcing the idea of water being evenly distributed within alpha-keratins.
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