Wet Wet Wet! New Publication – TRI Partners with KAO Corporations to Probe the Kinetics of Water Sorption

Trefor Evans, from TRI Princeton, along with Steven Breakspear, Crisan Popescu and co-workers from KAO Corporation have recently published an in-depth study that considers the kinetics of water sorption into hair and how bleaching or heat-treatment can impact upon the kinetics of moisture sorption processes.

S. Breakspear, T. Evans, P. Frueh, A. Neu, B. Noecker, C. Popescu, Q. Uellner

(Int. J. Cos. Sci., 2024, 00: 1 – 11, original paper and TRI Library entry)

Dynamic Vapour Sorption (DVS) technique used at TRI to investigate water sorption. The DVS measures the changes in hair weight as it is subjected to different air humidities.

Dynamic Vapour Sorption (DVS) is a gravimetric technique used at TRI to investigate water uptake and loss, and to create water sorption isotherms.  DVS data has classically been used to investigate the effects of various damage insults and hair treatments on water adsorption and desorption (For a nice introduction to DVS read this Chapter in ‘Practical Modern Hair Science’ written by Trefor https://library.triprinceton.org/1t0nsnb/340).

In this recent paper, the technique is used to investigate the kinetics of water uptake.  The authors propose a new mathematical model to describe hair water sorption into hair over time.  This model, for the first time, combines the kinetics of water diffusion into the hair, with the process of fiber swelling (driven by the relaxation of keratin chain entanglement), to provide a more accurate description of the DVS data.

Using this model, the authors show that:

• Kinetics experiments can give valuable information in relation to hair fibers’ internal structure and the degree of keratin entanglement.
  

• The rate of moisture uptake in the cuticle is faster than in the cortex over a range of humidities, and higher levels of chain entanglement exist in the cuticle versus the cortex up to around 70% RH.
  

• Bleached hair absorbs water that fastest, and heat-treated hair the slowest, at 60% and 90% RH.  Chain entanglement was highest in heat damaged hair, particularly at 30% RH.

For further information about the use of DVS within your hair research, contact us.