56 MEN’S GROOMING
Natural Formulation with xanthan gum For the natural formulation, the synthetic polymers were replaced by xanthan gum. Xanthan gum has thickening and fixative properties and can be used as an all-in-one biopolymer. Several xanthan gum types were tested at concentrations between 3% and 5%. Based on the rheological findings, the best formulation for a hair styling gel application was found to be 5% XG FNCS- PC. FNCS-PC is an 80-mesh xanthan gum with high transparency, specifically developed for personal care applications. The full formulation is shown in Table 2. This formulation is much easier to handle
and less time-consuming than the synthetic formulation. Xanthan gum was sprinkled into water while stirring until it dissolved completely. All the other ingredients could then be added. Xanthan gum is stable over a wide pH range and very salt tolerant.
Measurements of physical attributes Flow curve A Haake RheoStress 1 rheometer from Thermo Fisher Scientific with a parallel- plate system (PP20) was used to measure the flow curve at 21°C. The apparent shear viscosity was measured by increasing the rotational shear rate from 0.01 s-1
to 100 s-1 . This provides information about product
stability and product application. Low shear rates represent conditions during storage; the stability of the product at rest is evaluated. Increasing the shear rate causes stronger forces to deform the sample. Medium shear rates represent conditions when the hair gel is being applied.4,5
Oscillation measurement It is widely known that specific rheological parameters are very closely linked to the sensory perception of a cosmetic product.6,7 Information from oscillation measurement
100 G’ > G’’ gel 100
Table 1: Synthetic hair styling gel formulations Phase A
INCI Aqua Glycerine
A1 Acrylates/C10-30 Alkyl Acrylate Crosspolymer
B Sodium Hydroxide
VP/Methacrylamide/Vinyl Imidazole Copolymer
Solvent Moisturiser
Thickening polymer pH regulation
D Preservative
C Acrylates Crosspolymer-3 Fixative polymer Fixative polymer Preservation
Table 2: Natural hair styling gel formulation with Xanthan Gum Phase
Name A Water Glycerine Preservation Aqua Glycerine
A1 Xanthan Gum FNCS-PC Xanthan Gum B
C Lactic Acid 90% Heat Stable PC Grade
Lactic Acid
correlates directly with skin feeling and haptics. The rheology measurements were performed at 21°C using a modular compact rheometer (Anton Paar MCR 302 with a parallel-plate system (PP25)). Data were analyzed using RheoCompass software. As shown in Figure 1, the storage
modulus G’ [Pa], loss modulus G ’ [Pa], yield stress G’ (log) and flow point G’=G ’ were determined. For hair gel applications it is important
to define the gel character and gel strength. The gel strength is characterized by the solid portion of the product and can be analysed by measuring the storage modulus G’. The storage modulus determines the elasticity and gel character of the material. It is measured by placing
n G’ in Pa n G’’ in Pa INCI Function
Synthetic 1 Qs to 100 3%
0.5% Qs
–
15% Qs
Synthetic 2 Qs to 100 3%
0.5% Qs
10% –
Qs
Function Solvent Moisturiser
Thickening and fixative polymer
Preservative pH regulation
5% XG FNCS-PC Qs to 100 3%
5% Qs Qs
the sample between two plates. The upper plate applies shear deformation with increasing amplitude or strain through dynamic oscillation. The higher the value of the storage modulus, the higher the gel strength of the sample. In addition to the storage modulus G’,
loss modulus G ’ was measured. This characterises the viscous and thus the fluid part of the product. Another important parameter of cosmetic
products is their spreading behavior, which can also be evaluated by oscillation measurement. Yield point and flow point are two meaningful values to describe the spreading behaviour of a hair gel. The sample starts to flow at the yield
point, which marks the end of the linear viscoelastic range. At a certain applied stress, the lines of G’
and G ’ cross. This point is called the flow point. It is defined as the minimum stress that has to be applied to make the gel flow. The higher the flow point, the more difficult it is to spread the gel.5,8
10 0 0.001 0.01
0.1 γ
1 Figure 1: Oscillation curve: G’ and G’’ of a sample hair gel in relation to applied strain. PERSONAL CARE EUROPE 10
Texture analysis Stickiness is a relevant attribute in cosmetic science. Consumers expect a pleasant and not-too-sticky texture. The stickiness of a cosmetic product can be evaluated by a compression test. This was carried out with a Brookfield CT3 texture analyser, using a spreadability fixture (TA-SF). A specific cone- shaped probe penetrates the sample and then withdraws to its starting point. The texture analyser measures the force required to penetrate the sample and withdraw the probe (Fig 2). The force needed to penetrate the
November 2020
G’,G’’ (Pa)
Yield point
Flow point
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