COSMETICS AND BATHROOM PRODUCTS:HAIR GEL.

HAIR GEL

While a true gel is a hydrocolloidal suspension, cosmetic products gen- erally referred to as gels are semisolid in texture and usually clear to translucent in appearance. The viscosity of these products ranges from a thickened and readily pourable liquid gel to a semisolid stick. The product usually is in a thickened state within the squeeze tube or pump container and tends to decrease in viscosity during dispensation and application. Gel-type products may be water-based polymer gels or surfactant-based gels. Water-based gels usually contain alcohols to enhance clarity, product-thickening water-soluble polymers, resins, conditioning and moisturizing oils (e.g., lanolin, mineral oil, meadow-foam seed oil, sweet almond oil, safflower seed oil, castor oil), along with fragrance, preservatives (e.g., 1,3-bis[hydroxymethyl]-5,5-dimethylimidazolidine- 2,4-dione [DMDM] hydantoin, tetrasodium EDTA, diazolidinyl urea, methylparaben, propylparaben, ethylparaben), antioxidants (e.g., panthenol, tocopherol), coloring agents, and UV stabilizers (e.g., benzophenone-4). Surfactant-based gels (also called microemulsion gels) have a high vis- cosity and usually contain surfactants (e.g., triethanolamine), oils, and product-clarifying polyols (e.g., propylene glycol, glycerol, polyethylene glycol). Gels may also contain fruit and/or herbal extracts (e.g., apple, apricot, grapefruit, orange, sage, euphrasia, ginger root, Aloe barbaden- sis, chamomile, jojoba, rosemary, tea tree leaf, lavender, peppermint) to enhance gel formation and product quality as a hair treatment.

The function of a modern hair gel is to bond the hairs together and maintain hair styling and/or to provide conditioning (usually with an oil or conditioning polymer). Bonding activity is attributable to the presence of film-forming adhesive materials such as polymeric resins or fixatives. The most commonly used resins for this purpose are the water-soluble nonionic polymers PVP and/or poly-N-vinyl formamide. Thickeners are often added to provide stiffness and holding power. One of the most widely used synthetic gelling/thickening agents is a polyacrylic acid resin cross- linked with the alkyl ether of materials such as sucrose (a carbohydrate) or propylene, commonly referred to as carbomers. Carbomers require chem- ical neutralization (e.g., using triethanolamine) if added with PVP to avoid the formation of an insoluble PVP-carbomer complex. Other thickeners used include hydroxyethylcellulose, hydroxypropylmethylcellulose, algae, hydroxypropyl guar (gum), acrylates, PEG compounds, hydrolyzed wheat starch, and polyquaternium-11. Acids such as glycolic, citric, lactic, and/ or phosphoric acid are added as stabilizing agents, and agents such as oils, dimethicone, or glycerin are added to promote hair conditioning.

Because PVP has substantial humectant properties (and thus tends to absorb moisture in high humidity, causing the applied gel to become very sticky), alcohols (e.g., SD alcohol 40, ethanol, sorbitol) can be added to alleviate this problem. The addition of more humidity-resistant copolymers of PVP, such as vinyl acetate copolymer, allows the product to have increased resistance to moisture absorption. However, curl-activating gel products function by actually attracting moisture to the hair with the use of humectant polyols such as dimethylene copolyol.

Overall, hair gel should exhibit clarity in appearance, hair-holding capabilities under high humidity, pleasant odor, and the correct shear- thinning property to ensure even application of the product.