SILICONES
80 70 60 50 40 30 20 10 0
1.40 1.43 1.46 1.49 Refractive index Figure 5: Moisture permeability versus refractive index.
80 70 60 50 40 30 20 10 0
1.52
90% RH and 40˚C Ref point is dimethicone RI = 1.41 y = 16864 x –16.412 R2
= 0.9666
considered for a wide range of personal care products. The study brought forth two facts about
1.55 1.58
silicone that are important to highlight. First, it was demonstrated that silicone can be used and applied to hair to reduce frizz and help keep hair manageable. By reducing the amount of water allowed to penetrate through into the hair, water absorption in the cortex was mitigated and differential swelling was minimised. Because weather is uncontrollable, and most cannot avoid a humid day, those with difficult to manage hair should find relief in silicone’s ability to provide protection from the environment. Along with frizz control, silicone is known to promote smoothness, softness and shine. In addition, silicones are utilised to help some products maintain their quality and effectiveness long after purchase. The second fact to highlight is silicone’s
60% Diphenyl 40% Diphenyl 25% Diphenyl 10% Diphenyl Figure 6: Moisture vapour transport rate for various phenyl polymers (%mol). 12 10 8 6 4 2 0 0 6 12 Time (hours) Figure 7: Moisture absorption of treated and untreated hair. 64 PERSONAL CARE March 2012 18 24
Moisture uptake rate @30˚C, 90% relative humidity Control average Dimethyl Diphenyl substituted
100% Dimethyl
versatility, as noticed when comparing the phenyl-substituted silicone’s performance versus the standard methyl silicone’s performance in their ability to block moisture absorption in the cortex of the hair shaft. As seen in the study, both formulations blocked moisture when compared to the control. However, it was the ability of the modified silicone to exhibit even less moisture permeability that is of particular importance. This study helps highlight the benefits of having a material that can be optimised to better suit an application’s needs. By altering the substituent groups of the silicone polymer, many attributes can be targeted. No matter what industry silicone is used in, optimisations such as RI matching, hydrocarbon resistance and even decreasing the moisture permeability of a silicone are found to be beneficial. Understanding the link between the fields of personal care products and the physical chemistry of silicone assists product designers and formulators in meeting marketplace needs in a timely manner.
PC
References 1 Caruso J, Lambert J. Benefits of using silicones in personal care applications. NuSil Technology, 2010.
2 Robbins C. Chemical and physical behavior of hair 4th edn. New York: Springer, 2002.
3 Lipps N, Velderrain M. Moisture permeability of silicone systems. NuSil Technology, 2010.
4 Meyer J, Caruso J. Correlation between permeability of phenyl substitution on dimethicone and performance as a moisture shield in hair care products. NuSil Technology, 2010.
5 Silicones Environmental, Health and Safety Council. (2004, September). Silicones: Personal Care. Retrieved August 1, 2011, from
www.sehsc.com/PDFs/PersonCare.pdf
Mass (%)
Moisture vapour transport rate (gm/m2
/day)
Moisture vapour transport rate (gm/m2
/day)
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