Imagine you have just made a cream that feels nice, but is not perfect. If only it was a little thicker without being draggy, with a luxurious, cushiony feel. Or maybe you would like to make a water based face serum or gel? The answer is simple: polymers! Many are easy to use, economical and have the added benefit of increasing stability. Whether you are looking for something natural or synthetic, there are many choices to raise your lotion making to the next level.
WHAT ARE POLYMERS/GUMS?
Gums, or hydrocolloids are a diverse group of long chain polymers characterized by their property of forming viscous dispersions and/or gels when dispersed in water. There are many types of polymers and listed below are some of the more popular ones.
COMMON POLYMERS – NATURAL
• Guar gum is derived from the seed bean plant Cyamopsis tetragonolobus. The cationic version of guar is also popular as a conditioning agent for conditioners.
• Konjac, is derived from the roots of the elephant yam (Amorphophallus konjac) and pairs well with xanthan or the carrageenans.
• Xanthan, a by-product of bacterial fermentation, being anionic, is incompatible with cationics. It has good electrolyte tolerance and stability over a wide pH range.
• Carrageenans are obtained from red seaweeds (Chondrus crispus), and has different types of structures. Out of the three main types: kappa, iota and lambda, iota is the most widely used.
• Sclerotium gum is derived from the fermentation of Sclerotium rolfsii and provides a pleasant skin feel. It is tolerant to electrolytes and can “suspend” a small amount of oils but is fairly pricey.
COMMON POLYMERS – SYNTHETIC
• The cellulose derivatives, Hydroxyethylcellulose (HEC) and Hydroxypropyl methylcellulose (HPMC) are frequently used in liquid cleansing products such as shampoo or body wash. These surface active polymers require heating, with gelation temperatures ranging 50-85C, depending on the grade.
• Carbomer, a water-swellable acrylic acid polymer, is popular due to its elegant skin feel, versatility, clarity and suspension abilities. However it is sensitive to electrolytes so may not tolerate ingredients such as sodium pca, aloe vera, some types of protein, hyaluronic acid etc. Unless it is the pre-neutralised form (sodium carbomer), carbomer needs neutralising with a base such as sodium hydroxide in order for it to uncoil and thicken. This is usually performed after high shear mixing (stick blending) so as not to break down the polymer. Carbopol ultrez 20 is a popular carbomer type but there are many to choose from, with varying electrolyte tolerance, flow type, product type, suspension ability, clarity and sensory attributes.
• Use between 0.2-1.5% however, the natural types and cellulose derivatives, when used above 0.5% can result in snotty, slimy, stringy and sticky textures. Combining two polymers can often result in a synergistic effect which can be beneficial, helping to moderate the texture.
• Adding sufficient polymer to achieve high viscosity will not necessarily mean the polymer will also suspend particles such as mica. Xanthan and certain types of carbomer are recommended in this instance as they have good suspending properties.
• Polymers vary with regard to their thickening abilities at different pH levels. However, they generally prefer the pH range 5.5-8.5.
• Polymers are often supplied in different grades, xanthan transparent is good for clear formulations, some polymers are treated to reduce stringiness, improve hydration while others retard hydration making the polymer easier to disperse. Methocel 40-202 is popular grade of HPMC and Keltrol SFT a popular grade of xanthan.
• To ease dispersion and minimise clumping, add polymers to the oil phase instead of the water phase. After the water and oil phases are combined the polymer will begin to hydrate and thicken.
• 0.2%-0.3% xanthan and/or carbomer added to an emulsion helps strengthen the emulsion and provide a pleasant skin feel.
• Another recommended blend with desirable skin feel is a 50:50 mix of acacia gum and xanthan gum.
Polymers can be used to thicken and stabilise toners, creams, lotions, shower gels and conditioners. Although added at fairly low levels they greatly impact the quality and skin feel. Each polymer has its positives and negatives but when used effectively prove a very useful, if not, essential addition to a formulators toolbox.
“Creating Professional Products: Your Basic Guide to Polymers/Gums”, written by Jane Barber, was published in the November/December 2015 issue of Saponifier Magazine. It is reprinted here with full permission of the publisher, www.Saponifier.com”