50 FORMULATING FOR MILDNESS
Polyaldo® 10-1-CC
PEG-80 Sorbitan Laurate
Decyl Glucoside 60 Polyaldo® 10-1-CC
Decyl Glucoside PEG-80 Sorbitan Laurate
40
20
0 0.01 0.1 1 Concentration (mmo L-1) Figure 2: Foam image analysis of face washes with the different surfactants
no more than this amount of time generating foam, providing more real-world context to the data. Figure 2 shows a foam image analysis of
the three face washes, with the images taken at time zero (when the prototype formulation has achieved 150 ml of foam), 300 seconds and 800 seconds. The foam images for PEG-80 sorbitan laurate (centre) show it does not form a traditional foam matrix and support claims it is a poor surfactant. Compare PEG-80 sorbitan laurate to the other benchmark, decyl glucoside (right), and you can see the difference. Decyl glucoside creates large bubbles in high concentration which provides a dry, crackly foam. However, the walls of the bubbles are very thin. This leads to poor foam stability and will cause the foam to ‘crash’ or collapse on itself quickly. Polyglyceryl-10 caprylate/caprate mild surfactant forms spherical micelles, generates creamier foam and is more stable than PEG-80 sorbitan laurate and decyl glucoside. The micelles have thicker walls than the decyl glucoside bubbles, indicating more water and more surfactant in the walls. The additional surfactant helps support the bubbles and improve foam stability. The water-containing walls also contribute to a creamier skin-feel for a more aesthetically pleasing foam compared to decyl glucoside.
Table 1: Epiderm Skin Irritantion Test (SIT) Product
Polyaldo 10-1-CC
PEG-80 Sorbitan Laurate Decyl Glucoside
Cocamidopropyl Betaine
Phosphate Buffered Saline (negative control) 5% Sodium Dodecyl Sulfate (positive control) *Within the margin of error for 100%.
PERSONAL CARE EUROPE Figure 3: Dynamic surface tension analysis. Surfactancy attributes
Surface tension describes the value of the surface activity of a surfactant. It is a measure of a liquid and its ability to resist an external force due to the cohesive properties of its molecules. Surface activity is the measure of how well a surfactant can spread water across a surface.
A surfactant lowers the surface tension of the liquid in which it is dissolved. Measuring the surface tension of a liquid containing a surfactant helps scientists analyse the surface activity and performance — building and generating foam – of the surfactant. A high-performing surfactant will support foam stability as well as foam generation.
Surface tension study methodology A study was commissioned to measure the dynamic surface tension of surfactants with a Sigma 700 tensiometer (from KSV Instruments, Helsinki, Finland) using the Wilhelmy (platinum) plate method. Concentrations ranged from 0.001% to 3%. As with the foam generation studies, the Lonza scientists evaluated Polyglyceryl-10 caprylate/caprate mild surfactant, PEG-80 sorbitan laurate and decyl glucoside. As the concentration of Polyglyceryl-10 caprylate/caprate ester increases, surface tension decreases, leading to increasing surface activity. At >0.01% concentration
Mean Tissue Viability (%) Classification 104.5* 98.9 17.0 32.7
Non-Irritant Non-Irritant Irritant Irritant
100.0 3.1
Non-irritant Irritant
Polyglyceryl-10 caprylate/caprate average surface tension is about 27mN/m to 30mN/m (Fig 3). In general, an effective surfactant averages in the range of 25 mN/m to 32 mN/m.
By contrast, PEG-80 sorbitan laurate achieves a surface tension value no better than 39 mN/m. This result indicates PEG-80 sorbitan laurate is less surface active and indicates a less effective surfactant. The lower surface activity of PEG-80 sorbitan laurate also explains the minimal foam generation in previous data.
Irritation profile
Lonza contracted independent skin and eye irritation tests. These tests are in vitro alternatives to animal testing and industry standards for determining irritation potential for consumer safety. The Epiderm™ Skin Irritation Test showed Polyglyceryl-10 caprylate/caprate mild surfactant to be classified as a non- irritant surfactant on the skin (Table 1). To perform the test, the study utilised simulated human skin with in vitro skin cells, and inoculated them the various surfactants. The mean tissue viability is the percentage of skin cells left in the medium 60 minutes after inoculation. A mean tissue viability greater than 50%, indicating that the surfactant left more than 50% of the cells intact, classified a surfactant as a
Table 2: EpiOcular irritation test. Product
Polyaldo 10-1-CC
PEG-80 Sorbitan Laurate
Decyl Glucoside
Cocamidopropyl Betaine
32.3 256.0
Mean Tissue Viability (%)
Classification Mild Minimal
16.0 Moderate to Severe
<1.0 Severe April 2018 10
Increasing time
Surface Tension (mN m-1)
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