82 TEXTURES
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0
n Formulation A (with SC 25 NKW) n Formulation B (with SC 25 NKW) n Market Product (with SLES/CAPB)
Raw Materials
160 140 120 100 80 60 40 20 0
200 400 600 800 1000 1200 1400 1600 Time (s)
Figure 14: Time dependent increase of mean bubble area.
this plays an important role in shower products. It was shown that in the first 20 seconds, both formulations have a rapid foam forming ability and are competitive with the highly foaming market product (Fig 11b).
Lastly the foam structure was examined by means of time-dependent bubble size distribution of a foamed sample. Optical investigation was performed with DFA100 by measuring light refraction in a prism.10 Depending on whether the light beam hits a bubble or a wet lamella of foam, light is reflected to different degrees. This was then compared with average bubble size which can be determined by appropriate software. The foam structure of Formulation B and market product with SLES / CAPB is presented in Figure 12 and Figure 13. Recording of single images shows time dependent bubble size distribution at 2 minutes and 14 minutes after foaming. It can clearly be seen that the foam of Formulation B contains more wet lamellae (black areas) and fewer air bubbles per unit area than the market product (Fig 12). Thus we may say that the foam of formulations containing SC 25 NKW appear much finer and more moist as confirmed by testing the raw materials in the Ross-Miles test.
In comparison the foam of the market
product is drier and therefore less desirable when applied to skin. After a period of 14 minutes there is a clear difference in bubble size distribution of the two products. While Formulation B develops relatively small bubbles, the market formulation presents significantly larger bubbles which provide for a rapid degradation of the foam (Fig 13). The time dependent increase of bubble
PERSONAL CARE EUROPE Coco Glucoside
Perlastan SC 25 NKW/Coco Glucoside (1:1)
Perlastan SC 25 NKW
Market Product (With
SLES/CAPB)
Formulation A
Formulations
Fine porous foam
Formulation B
Figure 15: Comparison of mean bubble size after 10 minutes (the larger the bubbles, the more instable the foam) (active content of 3 g/l).
size is also displayed in Figure 14, where a significant difference between Formulation A, Formulation B and the market product can be seen. Foam structure of raw materials such as sodium cocoyl glutamate (SC 25 NKW), coco glucoside and their equivalent mixture (1:1) was also investigated. Ten minutes after the foaming process the average bubble size was determined and illustrated in Figure 15. SC 25 NKW as well as Formulation A and B with sodium Cocoyl glutamate present the finest foam with the smallest bubble size distribution.
Conclusion
Amino acid based surfactants provide a lot of positive characteristics, which are of great advantage for formulations of sulphate-free cleansing products. They show pronounced foaming behaviour with particularly high moisture content foam. This makes the products very attractive for rinse-off applications. In formulations, more aggressive surfactants such as SLS or SLES can be combined with Perlastan surfactants. The irritation potential of the main surfactant is greatly reduced and the resulting formulation benefits from much milder properties. In addition, buffer capacity of glutamate and sarcosinate surfactants in the range between pH 5.0 and pH 6.5 keeps the healthy condition of the skin intact. Furthermore, cleansing power of amino acid-based surfactants can be optimised through the combination with other surfactants which offer a lower CMC. Due to the excellent aerobic and anaerobic biodegradability Perlastan surfactants are classified as environmentally friendly. Sodium acyl glutamates from products such as Perlastan SC 25 NKW, Perlastan SC 25 NKPF, Perlastan SCG 50
ZPF and Perlastan SL meet different criteria of a wide range of certification processes and can be easily applied in natural cosmetics formulations.
PC
References 1 Sugar M, Schmukker R. Reduzierung der Hautadsorption von Sodium Laureth Sulfat: Ein neuer Weg, die Hautfeuchtigkeit nach Anwendung von Duschprodukten zu erhöhen, SOFW Journal 2001; 127: 3-5.
2 Kanari M, Kawasaki Y, Sakamoto K. J. Soc. Cosm. Chem. 1993; 27: 498.
3 Nnanna IA, Xia J. Protein-Based Surfactants. Surfactant Science Series 2001; 101: 261-270.
4 Husmann M, Weisse J, Wragg P, Wasko J. Perlastan Surfactants Derived from Naturally occurring Amino Acids. Cosmetic Science Technology 2008; 194-201.
5 Held E, Husmann M, Heinrich U, Tronnier H. Dermatological Compatibility of Amino Acid Based Surfactants – A Clinical Trial. SOFW Journal 2011; 137: 38-42.
6 Husmann M. Surface Active Agents Derived from Naturally-Occurring Amino Acids. CESIO - 7th World Surfactants Congress 2008.
7 Lee CH, Kawasaki Y, Maibach HI. Effect of Surfactant Mixtures on Irritant Contact Dermatitis Potential in Man: Sodium Lauroyl Glutamate and Sodium Lauryl Sulphate. Contact Dermatitis 1994; 30: 205-209.
8 Bilke-Krause C, Thomsen F. Dynamic Properties of Surfactants, Application Report. Homepage KRÜSS GmbH 2011.
9 Husmann M, Diederichs J, Wragg P. Glutamate Surfactants for Cosmetic Formulations. Schill +Seilacher GmbH 2007.
10 C. Bilke-Krause, T. Schörck, T. Winkler, Studies on the Stability of Foams, Application Report.Homepage KRÜSS GmbH 2010.
11 Analysis report for Schill + Seilacher. KRÜSS GmbH 2015.
September 2018
Mean Bubble Area (px)
Mean Bubble Area (px)
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