Considering hair styling, what could be more natural than simply combing or brushing hair? Or setting hair after shampooing and conditioning so that it dries in the desired style? In the latter case, wet hair is more flexible and deformable due to the hydrogen bonding of absorbed water with amino acids in the keratin protein fibers of the hair cortex. These bonds supplant the intermolecular bonds within the keratin itself, giving wet hair a malleability that allows simple styling without the need for styling additives. However, this hold is not very durable, especially in high humidity. The set relaxation time of simple water-styled coiffures depends on the relative humidity of the environment since it re-plasticizes the hair keratin. Hair care researchers have even devised mathematical formulas to define the process of curl set relaxation, which could be used to evaluate ingredients and formulations.1
While water-set, comb-and-go hair styling is enough for some, many consumers want something more substantial. The style they worked hard to achieve should last until they touch-up or restyle hair. This is one performance property required in a styling product. Common hair styling aids to help hold hair in place encompass a wide range of products; from polymer solutions delivered as simple liquid or foamed into mousse, to gels of varying viscosities and film stiffnesses. The essential elements of a natural hair styling liquid or gel are: a film-forming substance to keep hair in place, and a base to deliver it. This base may be as simple as thickened water or as complex as a gel or cream.
Hair Hold Technologies
Within the last few decades of hair polymer advances, a veritable avalanche of ingredients to hold hair has been invented. Now available to choose from are more than 100 polyquaterniums, and dozens of vinyl pyrollidone, vinyl acetate, acrylate and other copolymers; terpolymers; and more complex polymers for hair styling. However, under the guidelines of major “natural” certifying groups—i.e., NSF/ANSI 305, Ecocert, COSMOS, NPA and NaTrue—all of these synthetic polymers would likely be unacceptable. Thus, the natural hair care formulator must look elsewhere for materials with which to work.
In this regard, manufacturers and their product development teams often look to a major U.S. retailer in this mass-market space: Whole Foods, whose strict standards reflect the guidelines of the major certifying groups but do not follow them exactly. Table 1 reveals some differences between ingredients that are acceptable for simple placement in the store and, in a more elite category, that fall under the stricter Premium Body Care banner closer to the natural certifiers’ standards. Here it becomes clear that many conventional styling aids could be found simply placed on Whole Foods shelves, but many traditional synthetic polymers, such as carbomer for gel formation and polyvinylpyrrolidone (PVP) for hold, do not meet the Premium Body Care standard.
So where can one look for natural hair styling ingredients with true performance? Historic hair care provides some inspiration. According to Brockway and Hili, many natural materials were used by ancient cultures to style hair. The Egyptians employed gum resins and beeswax, while the Greeks and Romans used gums including Arabic (acacia), and albumin protein from egg whites to set hair.2
Shellac excreted by the female lac bug, Kerria lacca, apparently was used to make the hair lacquers used in Asian cultures to add shine and hold. Coconut oil and the fragrant variant monoi oil, an enfleurage of Tahitian gardenia petals, was used in Polynesia to condition and style hair as was shea butter, which is now used for skin softening and serves as a base for many natural pomades.2
Current natural hair styling aids on the market also provide some insight, as do specialty chemical suppliers—who are ever-diligent to develop new ingredients to improve product performance. To cover the full scope of natural hair styling products, one must consider both water-based gels and fluids, as well as oleaginous pomades and liquids. These are two distinctly different vehicles. One essentially evaporates out to leave a slight film residue and achieve a lasting hold. The other simply spreads on the hair shaft and remains substantially the same material as applied.
Raw Material Examples
Surveying the market for water-based gels, one will find both unmodified and modified natural polymers, the latter being designed to enhance functionality. Aloe vera gel often is employed as a base and sometimes replaces water as the primary ingredient, at least on the label. Two additional film-forming polymers that appear in many current products are acacia senegal gum and dehydroxanthan gum. The first is a natural tree bark product, purified but not modified. The second is a fermentation polysaccharide heat-treated by a proprietary technology. Note that these purely physical processing techniques would be acceptable by all aforementioned natural certifying schemes.
Acacia senegal gum, more commonly known as gum arabic, derives from a bark exudate of the North African Acacia Senegal tree, in the Leguminosae family. According to Dweck, this tree secretes an exudate from wounded branches that dries into a hard residue, which is purified for the commercial material. The main component of the carbohydrates present is arabin, a calcium salt of arabic acid, which is a five-carbon sugar acid.3
Gum arabic glycoproteins, including arabinogalactan-peptide and protein hybrids, having a molecular weight between 286,000 to 1.8 million, show reduced surface tension and enhance foaming, suggesting some surfactant activity. Even at these high molecular weights, solutions of them yield relatively low viscosities, e.g., 50-150 cps in 25% aqueous solution, and so can be used at high levels for hair setting. Gum arabic has been used as a stabilizer and binder in paints and coatings and food products such as candies.
Dehydroxanthan gum, on the other hand, produces viscosities between 20,000-35,000 cps in 1% aqueous solution, equivalent to or higher than its parent polymer, xanthan gum. According to one manufacturer, a gel using 1% dehyroxanthan guma was found to retain more than 90% of curl at both 90% relative humidity (RH) and 70°F, which lasted for more than 5 hr and up to 24 hr. This gel was compared with 4% PVP and PVP/VA polymer carbomer gels, which lost hold quickly and retained only 20% of curl after 5 hr. The limitation here may be that thickening and film-forming came from the same polymer, thus a firmer set may require being delivered from thicker products. In use, dehydroxanthan enhances wet comb and detangling, and can be restyled with water and without flaking.4
Other interesting styling polymers that have come onto the market are hybrid naturals, building on carbohydrate backbones and adding substituents known for their film-forming properties. Two novel derivatives are maltodextrin/VP copolymerb and hydroxypropyl starch phosphatec. The maltodextrin/vinyl pyrrolidone copolymer retains curl equivalently to its purely synthetic predecessor, PVP/VA, and better than PVP at 90% RH and 70°F. While this performance would not match that of current synthetic technologies, it gives the consumer an excellent, more natural and biodegradable product that is equal or superior to prevalent products that still rely on PVP.
The hydroxypropyl starch phosphate takes an amylopectin starch and chemically modifies it to be more compatible and have better clarity than its source carbohydrate. At 4%, this polymer delivers both styling and moderate thickening, ~10,000 cps, with wet curl retention equal to that of PVP. Although an anionic polymer, hydroxypropyl starch phosphate is both electrolyte-tolerant and affected little by pH levels ranging from 3.5-9.5.5
Additional work with natural polymers must move in the direction of improving hold and conditioning performance while abiding by the restrictions of the more widely accepted natural product certifiers. Among the acceptable chemical processes are: hydrolysis, condensation with elimination of water, esterification, transesterification, hydrogenation, hydrogenolysis, dehydrogenation, glycosidation, phosphorylation, sulphatation, acylation and amidation.6 This list of processes could generate a wide range of new products from available natural feedstocks, primarily polysaccharides and proteins.
Protein hydrolyzates: Protein hydrolyzates themselves find their way into numerous styling products—soy being one of the most common. These water-soluble polypeptides have average molecular weights of only about 2,000 Da, comprising varying combinations of all the protein-forming amino acids averaging about 10-20 residues per peptide. This molecular size does not allow for a true tertiary structure in solution, and these proteins are resistant to heat denaturing and compatible with modest levels of alcohol. They all form a clear or translucent cohesive film, adding to their hair-set properties, although they are highly susceptible to humidity droop. For plasticizing these films, use of a small amount of glycerin is typical.
Chitosan: One neglected natural polymer with both film-forming and conditioning properties is chitosan, an amino functional polysaccharide derived from the insoluble acetylated unit chitin. Chitin is composed of N-acetylglucosamine monomers. It is the main structural unit in the invertebrate kingdom, it is found in fungal cell walls, and it is analogous to cellulose in the plant kingdom. When deacetylated by hydrolysis, insoluble chitin becomes soluble polyglucosamine, which is available in a range of molecular weights to control aqueous viscosities.7
Most of the commercial material comes from shrimp shells, and this may foster reluctance to use it. Some researchers instead propose sourcing the material from discarded fungal biomass, which is increasingly available as a waste product from biofermentation.8 Note that chitosan must be neutralized, and lactic acid is most commonly used. When chitin becomes more widely available, the industry may see this unusual naturally cationic carbohydrate used more in hair and skin care.
One commercial chitosand product that has been on the market for years uses the humectant amino acid pyrrolidone carboxylic acid (PCA) as the neutralizing agent, and apparently, has a built-in plasticizer in the PCA.This marine-sourced ingredient may be the forerunner of a range of future fungal-derived chitin products.
Oil, butter and wax: At this point, a brief mention of oil-, butter- and wax-based products is in order. Petrolatum-based pomades of long ago have been replaced with plant oils such as castor and jojoba, stiffened with beeswax and shea butter. Note that both beeswax and lanolin remain on the Whole Foods Premium list although both are animal-derived. Also, organic beeswax can be sourced as an agricultural product to create USDA Organic hair pomades. Shea butter appears a more popular choice in these pomades, supplanting cocoa butter in many products. And since adjusting the wax levels in a pomade determines its stiffness, and varying oil components adjusts its shine, castor oil is sometimes preferred because of its substantial viscosity and shine—possibly due to its 1.473–1.477 refractive index.
Overall, there are many ingredient choices to formulate natural hair styling products that comply with major natural and organic standards; and many that have enough of a natural lineage to satisfy the final consumer. With the option for further derivation based on acceptable chemical and physical processes, the industry can expect second-generation ingredients to proliferate as the demand for more natural and sustainable products grows.
1. P Diaz and MYM Wong, Set relaxation of human hair, J Soc Cos Chem 3(4) 205-212 (Jul 1983)
2. B Brockway and P Hili, History of hair care, in Sustainable Cosmetic Product Development, W Schroeder, ed, Allured Business Media, Carol Stream, IL USA ch 5.4 (2011) pp 148-166
3. AC Dweck, Acacia Senegal, in Formulating Natural Cosmetics, Allured Business Media, Carol Stream, IL USA (2011) pp 164 and 523
4. H Cao, K Maurer and MJ Vitale, Dehydroxanthan gum, Happi magazine 82 (May 1, 2004)
5. Sustainable solutions for styling, Akzo-Nobel Global Personal Care brochure, http://viewer.zmags.com/publication/a55ab139 (Accessed Sep 17, 2013)
6. NaTrue Label: Requirements to be met by natural and organic cosmetics, www.natrue.org/fileadmin/natrue/downloads/Criteria_EN_1.9_FINAL.pdf (Accessed Sep 17, 2013)
7. B Brockway and P Hili, Chitin and chitosan, in Sustainable Cosmetic Product Development, W Schroeder, ed, Allured Business Media, Carol Stream, IL, USA ch 5.13 (2011) pp 182–183
8. GS Dhillon, S Kaur, SK Brar and M Verma, Green synthesis approach: Extraction of chitosan from fungus mycelia, Crit Rev Biotechnol epub (Oct 18, 2012)