Physical Process of Hair

 

Physical Process of Hair

Hair is a highly resilient structure and has been designed to withstand what can amount to a huge number of physical processes over its lifetime. The cuticle, with multiple layers, imparts significant resistance, and the f-layer helps to decrease surface frictional forces. The cuticle has great internal strength, with a surface that has low friction, and if a cuticle cell is removed, the cuticle cell below is merely left exposed with a fresh surface. 

 

A person may brush their hair up to 1000 strokes per month with the consequence that the cuticle structure is degraded, and eventually all the cuticles may be removed to reveal the less resilient cortex structure. The degradation due to these physical processes can take several forms. The first is abrasion of the cuticle edges, eventually leading to complete removal. Combing and brushing wet hair is more likely to lead to cuticle abrasion than combing and brushing dry hair due to higher friction forces.

Breakage may occur during combing and brushing. Under normal circumstances, the force required to pull a hair fiber out of the follicle is less than the force required to break a hair fiber. It might therefore be predicted that broken fibers would be rare.

However, several factors can lead to broken fibers. Excess chemical, UV light, and head exposure can eventually weaken hair sufficiently to lower the force to break of hair to less than that required to pull hair out of the scalp. If the fiber is caught up in a knot during combing, the local forces in the knot can be much higher, causing the fiber to break. Breakage is particularly an issue for curly hair since it is more likely to form tangles and knots leading to breakage, especially when wet. 

 

Physical processes causing cuticle damage and breakage will occur for almost all people but the severity of damage will vary according to hair morphology and habits and practices. Fine hair is more likely to break than thick hair simply because it has a lower tensile strength. Curly hair is more likely to break than straight hair due to higher abrasive forces between fibers and the likelihood of forming knots and tangles. This is especially the case for person of African Descent, in whom hair can be extremely fragile, especially if it has been regularly braided. Often cuticle removal is seen preferentially on the outside edges of the fiber, as this is the part of hair where frictional forces are highest. Products that include conditioning actives such as quaternary ammonium compounds and silicones are hugely impactful to reduce this physical damage and work by creating lower frictional forces on the hair surface, making combing easier, with lower knot and tangle formation.