Styling polymers on various hair types assessed

Differences between hair types are shown using high-humidity curl retention and assessment of mechanical properties as measured with a texture analyser (TA) assuming that the fibres were in omega loop configuration. Results from this study demonstrate that the stiffness of fibre assemblies of different hair types treated with different styling polymers is controlled by their differences in diameter. Fibres of smaller diameter such as Caucasian hair will have more fibres per unit volume which increases inter-fibre connectivity and thus stiffness. Theoretical explanations are provided based on physical models including the theory of deformation of thin rings to help explain differences in hair type. Furthermore, the difference in performance of styling polymers under high humidity has been reported and interpreted.

 The variety and versatility of today’s hair styles have accelerated the growth and expansion of many different hair-styling products all over the world. Consumers are seeking out products that they can use in various ways to provide stiffness, styling control and hold, as well as the enhancement of texture, shine, body, curl and condition of the hair. The market has grown steadily during the past decade and sales reached $9.0 billion in 2010.1 Growth has been particularly strong in the emerging markets of Asia, Latin America and Eastern Europe. New-product activity is driven by consumer diversity in ethnic, generational and psychographical attributes. This demand creates new research efforts comparing the effect of styling polymers on different types of hair. The surface topography of human hair, as defined by the outer layer of cellular sheets, termed cuticles, largely determines the cosmetic properties of the hair.2,3 Although there is no difference chemically between the major ethnic hair groups, each hair type, whether it is of Asian, Caucasian, African, or mixed racial descent, has a distinct morphological structure. Asian hair is thicker and rounder or less elliptical, and has more and thicker cuticles than Caucasian hair, while African hair is more elliptical. These structural differences, such as hair diameter and packing density, will definitely affect the performance of styling polymers under various environmental conditions. To expand our knowledge on the differentiation of the performance of styling polymers on different hair types, a comparison is made of Asian, Caucasian, mixed race and African-American hair with respect to the performance of hair-styling polymers. Testing includes the assessment of mechanical properties measured with a TA, assuming that the fibres are in omegaloop configuration, and moisture resistance obtained by both vertical and horizontal high-humidity curl retention (HHCR) methods. The results can help expand formulators’ selection, create highperformance styling products, and substantiate claims in extremely diverse markets.

Experiments