TEXTURES 101
LexFeel 699 (Pentaerythrityl Adipate/ Caprate/Caprylate/Heptanoate) is a branched/crosslinked polyester according to Figure 2 with shorter carbon chain (C6 – C10) end groups. The resulting polymer is fluid with a velvety texture and provides a similar function to castor oil in cosmetic formulations. The combination of the polar backbone and the hydrophobic character from the end groups provides for interaction with pigments resulting in even dispersion and flocculation prevention. This effect was demonstrated in two pigment dispersion tests where the viscosity was measured as an indicator of how well the base fluid wets the pigment. A lower viscosity measurement indicates better pigment wetting and this will translate to improved pigment dispersion in formulation. The results of the pigment dispersion test with Red No. 7 Calcium Lake at a 1:1 loading of pigment:dispersant is shown in Figure 5.
The viscosity of the 699 dispersion was lower than the dispersions with castor oil, polyglyceryl-2 triisotearate, and diisostearyl malate. A pigment dispersion test with micronised zinc oxide at a 1:2 loading of pigment:dispersant was also conducted. The viscosity of the 699 dispersion was 8,000 cP, lower than the dispersions with trioctyldodecyl citrate (10,000 cP), pentaerythrityl tetraisostearate (90,000 cP), tridecyl trimellitate (235,000 cP), and dipentaerythrityl tripolyhydroxystearate (23,000 cP). The smooth and uniform dispersion appearance of micronised zinc oxide in 699 after manual mixing for approximately 3 minutes is shown in Figure 6. The dispersion uniformity during application was evaluated for 699 and isotridecyl isononanoate with coated and uncoated titanium dioxide, at a 2:1 loading of pigment:dispersant (Fig 7). Pigment
colour. The higher OSI of 699 will result in better long term colour cosmetic formulation stability and a more true colour in formulation.
Figure 3: Lipstick formulation containing 5% (w/w) LexFeel Vibrant (left) and 0% LexFeel Vibrant (right).
dispersed with 699 has a smoother and more uniform appearance upon application with both variants of titanium dioxide. Pigment dispersion in clean ingredient
formulations is often accomplished with oils, such as castor oil. An inherent disadvantage to natural oils is their susceptibility to oxidation. This can sometimes be improved with the addition of antioxidants but this generally only prolongs the oxidation by a marginal amount. The oxidative stability of 699 was compared with castor oil using the Oil Stability Index (OSI), which is the point of maximum change of the rate of oxidation. The test was carried out on a Rancimat according the American Oil Chemists Society (AOCS) Official Method Cd 12b-92. The OSI at 110C of castor oil and 699, respectively, was 57.1 hours (yellow appearance) and 75.2 hours (colourless appearance). This indicates a superior oxidative stability of the polyester. The castor oil OSI was improved to 60.8 hours with the addition of 0.3% Tocopherol however the appearance was still yellow in
Polyester ingredients align with clean beauty lifestyle The 12 Principles of Green Chemistry were introduced in the late 1990s as a collection of ways to reduce both the environmental impact and the potential negative health effects of chemicals and chemical synthesis.4 The polyester ingredients discussed here were designed and manufactured according to many of the Principles of Green Chemistry. The starting materials are benign to both the environment and human safety. The polymers that result are equally nontoxic to humans and the environment. LexFeel Vibrant is partially derived from palm acid which is responsibly sourced according to the RSPO Mass Balance supply chain. During production, a one-pot solvent-free process is employed and this process produces no waste. The only by-product is water. The resulting polyesters are biodegradable and contain >70% biobased content. By using these novel polyesters in colour cosmetic applications, consumers can trust in the safety and low environmental impact of the ingredient and receive the strong performance benefits they expect.
Figure 4: Lipstick formulation applied to consumer containing 5% (w/w) LexFeel Vibrant (left) and 2.5% (w/w) Beeswax + 2.5% (w/w) Ozokerite (right).
November 2019
Engaging textures and sensations Another important consumer delighter in the colour cosmetics market space is the creation of interesting and engaging textures and sensations while continuing to honour the Clean Beauty lifestyle. As noted previously, esters, the starting materials of polyesters, are benign ingredients that are safe for both humans and the environment. SustOleo TL (Trilaurin) is a known ester that has been redeveloped by INOLEX according to the 12 Principles of Green Chemistry. Both the glycerin and lauric acid are derived from coconut oil, resulting in a non-palm version of Trilaurin. Trilaurin creates interesting textures and sensations in water-based formulations, providing a fast melting sensation on skin with a slight cooling effect. The after-feel has a distinct powdery character similar to the sensory effect of some silicone elastomers. This dual melting and powdery experience can be attributed to the unique melt profile of SustOleo TL. Traditional esters and oils exhibit a distinct melting temperature as measuring by Differential Scanning Calorimetry (DSC). Traditional butters can exhibit either a distinct melting temperature or a melting temperature range. Trilaurin exhibited a unique melting profile with two distinct melting temperatures: 29.9 °C and 43.9 °C. This is characteristic of a polymorphic crystalline structure – two distinct crystalline phases – which results in a distinct sensory profile in formulation.5
As such, Trilaurin was used to create new formulation PERSONAL CARE ASIA PACIFIC
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