Hair has amazing properties including its unique structure and steel like strength. Now new research is exploring the use of hair in many unknown areas including the making of body armor to protect police personnel.
The new pitch on using hair for armor has been raised by researchers from the University of California. They examined hair at a nano level to leverage the strong properties in the making of body armor.
They noticed that hair can be stretched to one and a half times the original length before it breaks.
"Hair is such a common material with many fascinating properties," noted Bin Wang, co-author and an alumna of UC San Diego in the Department of Mechanical and Aerospace Engineering.
Ideal Properties For Protective Gear
To understand the extraordinary property of deforming and stretching, the researchers worked on different conditions and found that hair withstands 80 percent deformation with no breaking and can revert to its original shape when stressed.
These were also the prime properties required in making protective gear.
The study has been part of the effort to develop synthetic materials from naturally occurring biological materials, according to Marc Meyers, the lead author and a professor at the UC San Diego Jacobs School of Engineering.
The findings have been published in Materials Science and Engineering C.
Meyers compared the behavior of hair to honey that is also highly viscous. He noted that when honey is deformed it becomes stiff and if done slowly it becomes easy to pour.
Leveraging The Structure
Hair is made of two parts — cortex and matrix. The former has fibrils and a random structure with sensitivity to speed on deformation while the cortex is neutral. Jointly, these components give hair the ability to withstand all stress and strain.
Made of coiled spirals chain known as alpha helix chains, fibrils have alpha helixes that uncoil and turn into beta sheets when hair is deformed. Such a transition allows hair to handle greater stress without undergoing any cracking.
Stretching And Impact Of Water
During the experiments, the researchers found that increasing humidity makes hair withstand 70 to 80 percent deformation before breaking.
There is 'softening effect' by water as it enters the matrix and ruptures the sulfur bonds in the filaments of hair strands. They also noted that at 140 degrees Fahrenheit (60 degrees Celsius) hair gets permanent damage if stretched.
"We wanted to understand the mechanism behind this extraordinary property," said Yang (Daniel) Yu, a nanoengineering Ph.D. student at UC San Diego and the first author of the study.
Stretching under a smaller strain restores the hair to its original shape while further stretching leads to an irreversible transformation.
Beyond this, hair breaks rapidly under lower stress and strain. If the stretching speed is changed, results also vary. That means faster stretching can make hair stronger.
