MEN’S GROOMING 57
250 200 150 100 50 0
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46 8 10 12 Time (s) Figure 2: Compression test of two samples with significantly different texture profiles.
sample (positive peak maximum) characterises the firmness. The force required to withdraw the cone and break the contact between probe and sample reflects the adhesiveness (negative peak maximum). It correlates directly to the sensory perception. The positive section represents the spreadability and the negative section the stickiness. The higher the adhesiveness, the more elongated the cling formation and the stickier the product.5 Sample one is firmer and more adhesive
than sample two. In addition to rheology, the performance of the formulation was analysed using two established industry methods – the curl retention test and a sensory evaluation.
Curl retention test The curl retention test characterises the hair styling properties and humidity resistance of a styling gel. 0.5 g of each test product was applied to wet tresses of natural European bleached hair. Three replicate tresses were shaped into curls by winding them onto hair rollers for 24 hours. The tresses were then stored in a climate
10,000,000
chamber at a temperature of 21°C and a relative humidity of 75%. After certain time intervals (15 minutes, 30 minutes, 1 hour, 5 hours, 24 hours), the length of the curls was measured and documented photographically. The longer the shape of the curl is maintained and the shorter the tresses appear, the better the product’s curl retention performance.
Sensory evaluation Again 0.5 g of the test product was applied to European bleached hair. A panel of trained experts then evaluated the attributes fixation, combability, residues, static charge after combing, and ease of application. A paired comparison test was conducted according to DIN/ISO 5495.9
Results and discussion Analysis of several benchmark products provided data for the creation of representative formulations. A target range for the viscosity measurements was then defined based on the data obtained. Since the products differed widely in terms of
n Synthetic 2 n Synthetic 1 n 5% XG FNCS-PC
oscillation data, no specific target range was determined for this parameter. Analysis of the benchmark products using the texture analyser revealed substantial variation in respect of firmness and adhesiveness. This means that there was no specific target value that had to be achieved.
Formulation testing To evaluate the performance of xanthan gum as a natural thickening and fixative agent in hair styling gel, a formulation containing xanthan gum was compared to two synthetic formulations that were developed in-house. The formulations were characterised for rheology, texture profiles and performance. Xanthan gum demonstrates shear
thinning behaviour. At very low shear rates it shows high viscosity and excellent stabilising properties. Viscosity is reduced at higher shear stress, giving good distributability and pleasant haptics. Hence, xanthan gum FNCS-PC provides excellent rheological properties for hair styling gel applications.4,5 As regards flow behaviour and viscosity,
1,000,000 100,000
a slightly more pronounced shear thinning behaviour was observed with the xanthan gum formulation, although at very low shear rates the formulations had the same viscosity (Fig 3). All in all, the differences are very small and not readily apparent to the consumer. The results of the oscillation measurements are presented in Figure 4. Big differences are only detectable by
10,000 1,000 0.01 0.1 1 Sheer rate (s-1 ) Figure 3: Rheology results: flow curves of two synthetic formulations and one natural formulation. November 2020 10 100
evaluating the storage modulus G’ and the yield point. The formulation with XG FNCS-PC features the smallest storage modulus G’. This means that it contains the weakest gel structure or elastic portion. Formulations Synthetic 1 and 2 show quite high storage modulus values and thus a stronger gel structure compared to XG FNCS-PC. The same is true for the yield point values. Comparing the values of loss modulus G ’
10 PERSONAL CARE EUROPE 14 16 18 20
n Sample 1 n Sample 2
Viscosity (Pa.s)
Load (g)
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