Comparatively Speaking: Cushion vs. Playtime vs. Hardness

By: Anthony J. O'Lenick Jr., Siltech LLC

Posted: June 21, 2011

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In most compounds the cushion and playtime are directly related. Honey has both a high cushion and high playtime. There are materials that have a good cushion but rapidly collapse to have a low playtime. Multi-domain alkyl silicone compounds having both liquid and solid portions in the same molecule and therefore are important materials for high cushion and low playtime. There are many applications in which in a high level of cushion and a short playtime are desired. These include lipsticks, sun products and many lotions.

Hardness

Hardness can be tailored with esters, and there are three major ways in which the hardness of an ester can be modified: reduction of carbon number, introduction of unsaturation, and introduction of branching.

Reduction of carbon number: The liquidity of an ester increases with decreasing carbon number. Behenyl behenate has a carbon number of 44 and a melt point of 68°C. Stearyl stearate has a carbon number of 36 and a melt point of 62°C. Decyl deconate has a carbon number of 20 and a melt point of around 9°C. While the liquidity increases with decreasing carbon number, the odor also has a tendency to increase as the reactants have more odor.

Introduction of unsaturation: The introduction of unsaturation into an ester result in more liquid products, but they need to have antioxidants present to retard rancidity. Saturated stearyl stearate has a carbon number of 36 and a melt point of around 62°C. Di-unsaturated oleyl oleate also has a carbon number of 36; however, it has two unsaturated groups present and a melt point around -5°C. Saturated behenyl behenate has a carbon number of 44 and a melt point of 68°C. Behenyl erucate has a carbon number of 44, but one unsaturation. It has a melt point of 45°C.

Introduction of branching:  Branching is an efficient way to achieve liquidity. Linear stearyl stearate has a carbon number of 36 and a melt point around 62°C. Di-branched isostearyl isostearate also has a carbon number of 36; however, it has two branched groups present. It has a melt point of around -5°C.