2023-09-30 07:00:00
For the first time, it was possible to analyze, at a molecular level, the damage to the structures of hair strands that have undergone straightening or bleaching. To accomplish the feat, researchers from the Physics Institute (IF) at USP used a physics technique called X-ray scattering. In a simplified way, the method works like shining light on an object to see its reflection and better understand its shape and composition.
Among the samples analyzed, the hair that went through the straightening process and then bleaching were the ones that suffered the greatest damage. The strands have four times more porosity than the strands, resulting in dry, brittle hair, with frizz and little elasticity.
Details of the research, carried out in partnership with the University of Copenhagen, Denmark, were published by Journal of Applied Cristallography.
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How does X-ray scattering work?
A device directs beams of X-rays to strands of hair being analyzed. The X-ray photons penetrate the strands and interact with their internal structures. (2D) on the other side. This process allows detailed information to be obtained about the changes that have occurred in the microstructures of the hair fibers. X-ray scattering technique – Image provided by researcher Cibele Castro Lima to Jornal da USP
To achieve the result at the molecular level, professor Cristiano LP de Oliveira, from the Department of Experimental Physics at IF, said in an interview with USP Newspaper that it was necessary to combine different techniques:
The work on damage to hair structures in straightened hair was carried out using an innovative methodology combining several techniques (X-ray scattering, analytical terms, mass spectroscopy and thermogravimetry) in order to understand the global properties of hair fibers on a wide range of scales. of size.
Procedure details on samples:
The active ingredient used in the tests contains glyoxylic acid associated with carbocisteine, which is not permitted by Anvisa (National Health Surveillance Agency), but is present in most straightening products. The natural hair samples used were obtained from a supplier in the United States. .They were separated into three distinct groups: in the first, subjected to discoloration; in the second, straightening; and in the third, the strands were subjected to both procedures, being bleached and straightened. The researcher introduced a heat source in the X-ray scattering experiment to simulate the reheating of hair fibers after a straightening procedure
The experimental data were collected by the central multiuser of the IF, which has state-of-the-art equipment for X-ray scattering and diffraction studies.
The result may be beautiful on the outside, but the inside is another matter.
In an unprecedented way, X-ray scattering revealed that the progressive, harmless, is nothing. The external result may be beautiful and please many people, but the truth is that hair loses much more than it gains.
The acid straightening process causes changes in the lipid layers. These layers make up the cell membrane complex and play a crucial role in maintaining the smoothness, shine, flexibility and strength of the hair. A type of hydrophobic film is formed around the hair fiber that retains water molecules inside the fiber and makes it difficult for cosmetic products to penetrate, even when exposed to high temperatures.
Image: provided by the researcher to Jornal da USP
And when discoloration is added to the chemical straightening procedure, the result is even more disastrous. Bleaching causes loss of important proteins and lipids that make hair even more sensitive.
The research also identified the denaturation of the alpha-keratin protein, which provides strength and elasticity to the hair fiber. This denaturation is directly proportional to the increase in temperature or the time the straightener is exposed to the hair. The damage is greater at higher temperatures, affecting both the cortex and cuticle, and is irreversible.
The immediate result of the progressive brush is beautiful because the product forms a film around the surface of the hair, leaving the strands shiny, aligned, silky, free of frizz, volume and ripples. However, it is a false impression that the hair is healthy and treated.
Cibele Castro Lima, author of the research, chemical engineer and post-doctoral researcher in the Complex Fluids Group at IF.
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