Thermal And Mechanical Transitions In Keratins And Their Relevance For Hair Cosmetics
January 2006
keratin hair cosmetics stress-strain behavior synthetic polymers helical segments humidity temperature glass transition temperature physical aging denaturation keratin composition Differential Scanning Calorimetry bleaching perm-waving intermediate filaments associated proteins reductive damage α-helix unfolding DSC
TLDR High temperatures and cosmetic processes can damage hair keratin, affecting its structure and strength.
The study explored the thermal and mechanical properties of keratin fibers, such as those found in hair, and their implications for hair cosmetics. It was found that keratin fibers exhibit stress-strain behavior similar to synthetic polymers, with specific transitions linked to structural changes in helical segments. The study highlighted the importance of humidity and temperature on these transitions, noting that keratin fibers typically operate below the glass transition temperature, where physical aging occurs. High temperatures lead to denaturation of helical filaments, with variations depending on keratin composition. Differential Scanning Calorimetry (DSC) was used to assess changes in keratin due to cosmetic processes like bleaching and perm-waving, revealing that both intermediate filaments (IFs) and associated proteins (IFAPs) are affected, with bleaching impacting both similarly, while reductive damage is more pronounced in IFs. The study concluded that the matrix's hindrance of the α-helix unfolding is a key factor in the denaturation process.