Thermomechanical Analysis of Natural and Cosmetically Treated Hair
There are, however, risks associated with many types of treatments and it is important to be fully aware of possible adverse effects in order to choose a safe treatment. Thermomechanical analysis (TMA) is a good technique to characterize the mechanical and physical properties of hair.
Figure 1: TMA sample holder for fiber measurements
with a hair sample installed.
Introduction
Thermomechanical Analysis (TMA) measures the expansion and shrinkage behavior of materials as a function of time or temperature while they are subjected to a defined force [1, 2].
Different measurement modes with suitable clamping accessories are available. These allow bars, films or thin fibers like hair to be analyzed.
Even very fine hairs can be mounted in the tension accessory with the aid of copper clips.
In this application example, two different hairs, an untreated natural hair and a natural hair that had been subjected to a shine and bond hair treatment, were measured in the tension mode up to a temperature of 230 °C. The hair samples were compared with regard to their shrinkage and expansion behavior and thermal stability.
Hair from the head of a human being is a natural fiber produced by keratin, a protein containing a high concentration of sulfur originating from the amino acid cysteine. The cortex occupies most of the hair area. The keratin fibers of the cortex make the hair strong; its long chains are compressed and form a regular structure. The most important physical property of hair is resistance to tear, but elasticity and hydrophilic properties are also important.
In general, hair treatments are commonly used to obtain a desired appearance, shape or texture. However, treatments can cause damage to the hair on a molecular level resulting in hair that looks dry, thin and weak. The desire for products that improve the appearance and feel of hair has created a huge industry for hair care.
Characterization of the structure and physical and mechanical properties of hair are essential for the development of innovative cosmetic products. Techniques like TMA can be very useful for this type of work.
Experimental Details
An untreated natural hair and a natural hair after a shine and bond hair therapy were investigated by TMA and the results compared. The procedure for hair therapy involves several steps that are described below. First, the hair was examined with regard to texture, porosity and history of former chemical treatments. The hair was then washed with a cleaning shampoo...
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Conclusions
Thermomechanical Analysis is an excellent technique for characterizing the expansion and shrinkage behavior and the thermal stability of thin fibers like hair. The TMA fiber clamping accessory with copper clips allows very fine fibers to be easily and reproducibly mounted.
In these studies, the effect of a special hair therapy was investigated. The hairs were measured and compared before and after hair therapy. The results obtained were very reproducible and showed that the treated hair showed greater thermal stability than the untreated natural hair and confirmed the positive effect of the hair care treatment.
The TMA technique and the resulting information can therefore be of great use for developing products in the cosmetic industry and for obtaining information about their effects on hair.
Thermomechanical Analysis of Natural and Cosmetically Treated Hair | Thermal Analysis Application No. UC394 | Application published in METTLER TOLEDO Thermal Analysis UserCom 39