Wortmann Franz J, Wortmann Gabriele, Haake Hans-Martin, Eisfeld Wolf
School of Materials, University of Manchester, Manchester M13 9PL, United Kingdom (F.J.W., G.W.) and BASF Personal Care and Nutrition GmbH, 40589 Duesseldorf, Germany (H.-M.H., W.E.).
J Cosmet Sci. 2017 Mar/Apr;68(2):173-182.
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 ″. The results show an increase of ″ with a drop of ' and , as is expected for a viscoelastic material well below its glass transition. The overall power of ″ to discriminate between samples is quite low. This is attributed to the systematic decrease of the parameter values with increasing fiber diameter, with a pronounced correlation between ″ and '. Analyzing this effect on the basis of a core/shell model for the cortex/cuticle structure of hair by nonlinear regression leads to estimates for the loss moduli of cortex (″) and cuticle (″). Although the values for ″ turn out to be physically not plausible, due to limitations of the applied model, those for ″ are considered as generally realistic against relevant literature values. Significant differences between the loss moduli of the cuticle for the different samples provide insight into changes of the torsional energy loss due to the cosmetic processes and products, contributing toward a consistent view of torsional energy storage and loss, namely, in the cuticle of hair.
对单根人发进行扭转分析特别适合于确定角质层的特性及其在美容加工过程中的变化。通过使用扭摆法进行自由扭转振荡获得的两个主要参数是储能模量（'）和损耗模量（″）。基于先前关于'的研究工作，当前的研究重点是″。结果表明，随着'和的下降，″会增加，这对于远低于其玻璃化转变温度的粘弹性材料来说是预期的。″区分样品的总体能力相当低。这归因于参数值随着纤维直径的增加而系统性下降，″与'之间存在明显的相关性。通过非线性回归基于头发皮质/角质层结构的核/壳模型分析这种效应，得出了皮质（″）和角质层（″）损耗模量的估计值。尽管由于所应用模型的局限性，″的值在物理上不合理，但与相关文献值相比，″的值通常被认为是现实的。不同样品角质层损耗模量之间的显著差异有助于深入了解由于美容过程和产品导致的扭转能量损失的变化，从而有助于形成对扭转能量存储和损失的一致看法，即在头发的角质层中情况。
