Hair conditioning technology with more sustainable materials

Motivation: Botanical oils, as sustainable alternatives of silicone oils, are the emollients in silicone-free hair conditioning formulations. However, they do not deposit on hair surface as easily and evenly as silicone oils do, resulting in less conditioning effects and worse sensorial perception, especially on highly damaged hair.

Results: Atomic force microscopy (AFM) was deployed to characterise the impacts of aging and chemical damage on hair morphology and surface interactions. Compared to single damage effects which both lead to less intact cuticle structures and slightly higher surface adhesions on hair, the combined damage strips cuticle layers, and increases average hair surface adhesion by 53% which causes higher combing frictions on dry hair. Together with a 62% lower mean elastic modulus and a 39% lower mean break stress compared to wet virgin hair, highly bleached hair shows a mean detangling force 6.6 times as much as virgin hair at semi-dry status, with significantly more breakage of fibres during combing tests. 
Regression model of oil lubrications investigated using a customised tribological apparatus were generated to identify the optimum oil viscosity (10 - 10000 cSt) and film thickness (5 - 500 nm) on highly damaged hair modelling substrates at different contact pressures (0.005 & 1 MPa) and sliding velocities (5 & 15 mm/s). In rubbing and detangling tests on treated hair tresses, the detangling lubrication is found to be dominated by oil viscosity for both kinds of oils, and the rubbing lubrication, for botanical oils, is determined by both oil viscosity and deposition, while only oil viscosity affects silicone oil rubbing lubrication.

Significance: Damage to hair surface is studied to develop better strategies to achieve desired deposition. Lubrications of oils are correlated to their intrinsic properties and will further be correlated to compositions for optimising conditioning formulations with botanical oils.