The Strength Of Human Hair Is Comparable To Steel
Human hair is regarded as a person's "crowning glory". Besides its aesthetic appeal, human hair, specifically its strength, is comparable to steel. This characteristic of human hair has lead scientists to study its structure and behavior to develop synthetic materials for body armor and improve haircare products.
The strength of human hair is comparable to steel. This is because it can be stretched up 1.5 times its original length before breaking. By investigating this characteristic of human hair, scientists from University of California San Diego, are not only hoping to understand the structural and behavioral properties of the human hair but also develop materials based on these properties that are better than existing ones.
The scientists examined hair on the nanoscale level, particularly how a strand of hair is deformed, stretched, and behaves were scrutinized. The team of scientists found that hair behaves depending on how fast or how slow it is stretched.
When hair is stretched slowly, it breaks easily. But when hair is stretched fast, it becomes stronger to the point that it won't break easily.
The study explains that this behavior of hair is because of its main parts, the cortex fibrils and matrix. The matrix of the hair is sensitive to the speed the hair is stretched or deformed while the cortex is not. On the other hand, the cortex fibrils in the hair, made up of thousands of alpha helix chains are structural changed when hair is stretched or deformed.
As the hair is stretched, the alpha helix chains uncoil and become beta sheets. By changing from alpha helix chains to beta sheets, the hair withstands high stress and strain and handle being stretched longer than its original length before breaking.
The structural changes the hair undergo is partially reversible. According to the study, published in Materials Science and Engineering: C, when hair is deformed by a small amount of strain, it can revert to its original shape.
On the other hand, when too much strain is exerted on the hair, the structural changes become irreversible, meaning the alpha helix coils stay as beta sheets.
In addition, when hair is exposed to 60 degrees Celsius temperature, it is damaged permanently. In temperatures higher than that, it breaks faster at lower stress and strain.
When hair is exposed to 70 to 80 percent humidity levels, it can withstand being stretched before breaking. Water also contributes to the structural change in hair. It softens it and breaks down the sulfur bonds in the hair filaments.
By establishing the structural and behavioral properties of hair, the scientists hope to develop materials that have the same properties but are more effective than existing products. Not only will it be light-weight, it will have the strength comparable to steel particularly recommended to be used as body armors.
Plus, targeting these properties of hair, developers of cosmetics and care products can develop products that will keep hair healthy.