DMA analysis: Active penetration and more
Dynamic mechanical analysis (DMA) has been used to characterize polymers for over a century. However, few researches have been made to characterize hair, a natural polymer consisting mainly of keratin.
This article highlights the power of this technique to study hair active penetration and presents some observations made that proves its powerfulness and raises questions regarding the hair damage prevention to straightening and bleaching treatments.
Several methodologies were developed in the past in order to evaluate active penetration into hair (1-16). However, few of them have explained how the actives can change or alter the behavior of hair. It is known from the literature (17) that the hair is divide in three major components: cuticles, the external surface of hair; cortex, the inner and more prominent component; and the controversial hair medulla located in the central part of the hair, which can be seem in most mammals hair fibers but in some human hair fibers it is missing. Therefore, its role in human hair fiber it is still a mystery.
The hair surface plays an important role in the visual aspect of the hair such as shine (18-31), in its properties related to frictional forces such as feeling by touching and combing and in the hair hydrophobic behavior related to the 18-MEA layer (17, 32-37).
The cortex is responsible, mainly, for the shape, color appearance and mechanical behavior of the hair (17, 38-41). The penetration of an active into the hair will set in the cortex (or medulla) and, therefore, change its molecular structure le ...