Rheological and texture analysis methods for quantifying yield value and level of thixotropy / Slobodanka Tamburic in SOFW JOURNAL, Vol. 143, N° 6 (06/2017)  

[article]  inSOFW JOURNAL > Vol. 143, N° 6 (06/2017) . - p. 24-30 Titre : Rheological and texture analysis methods for quantifying yield value and level of thixotropy Type de document : texte imprimé Auteurs : Slobodanka Tamburic, Auteur ; Helen Sisson, Auteur ; Milica C. Stevic, Auteur ; Neil Cunningham, Auteur Année de publication : 2017 Article en page(s) : p. 24-30 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Cosmétiques -- Texture Emulsions -- Emploi en cosmétologie Formulation (Génie chimique) Rhéologie Thixotropie Index. décimale : 668.5 Parfums et cosmétiques Résumé : The objective of this study was to compare different methods for the assessment of yield stress and level of thixotropy in semisolid emulsions, using three instruments ; an air-bearing controlled-stress rheometer, a T-bar viscometer and a texture analyser. The following methods were used to assess the yield stress : a low-rotation T-bar test, a shear stress sweep, a shear rate sweep, an oscillatory stress sweep and an immersion/de-immersion test on the texture analyser. The level of thixotropy was assessed by : a hysteresis loop test, a three-step thixotropy test and a repeated immersion/de-immersion test. A good linear régression fit was found between increasing polymer concentration and yield stress measured by the T bar test, oscillatory stress sweep and immersion/de-immersion test, while no such fit existed in the cases of the shear rate sweep and shear stress sweep. There was good correlation between the two rheological methods for detecting the level of thixotropy, the hysteresis loop and the three-step thixotropy test. The most consistent yield value results were obtained using the low-rotation T-bar test and the oscillatory stress sweep test. Under the experimental conditions of this study, bath three-step thixotropy and hysteresis loop test have proven reliable in assessing the level of thixotropy. The repeated immersion/de-immersion test could also be employed to provide information on irnmediate structural recovery. Note de contenu : - Quantifying the yield stress - Quantifying the level of thixotropy - Table 1. The formulation of the semisolid w/o emulsion used in the study - Table 2. Yield stress values obtained using six different methods, five experimental and one based on mathematical model (Hershel-Buckley equation) En ligne : https://drive.google.com/file/d/1G-wIwT08zGStmeFJJEai0BlJEEbEb8aD/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=28730 [article]

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Rheological and texture analysis methods for the assessment of viscoelasticity / Slobodanka Tamburic in SOFW JOURNAL, Vol. 144, N° 6 (06/2018)  

[article]  inSOFW JOURNAL > Vol. 144, N° 6 (06/2018) . - p. 20-25 Titre : Rheological and texture analysis methods for the assessment of viscoelasticity Type de document : texte imprimé Auteurs : Slobodanka Tamburic, Auteur ; Milica C. Stevic, Auteur ; Helen Sisson, Auteur Année de publication : 2018 Article en page(s) : p. 20-25 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Carbomères Les carbomères sont des polymères synthétiques hydrophiles d'acide acrylique. Les carbomères sont utilisés comme émulsions stabilisatrices ou comme agents épaississants ayant l'apparence d'un gel aqueux dans l'industrie pharmaceutique ou cosmétique. L'aminométhyl propanol permet de les stabiliser sous la forme d'un gel. Cosmétiques -- Analyse Cosmétiques -- Texture Emulsions -- Emploi en cosmétologie Formulation (Génie chimique) Gomme de xanthane La gomme xanthane est un polyoside obtenu à partir de l'action d'une bactérie, la Xanthomonas campestris. Elle est soluble à froid et est utilisée comme additif alimentaire sous le code E415 pour ses propriétés épaississantes et gélifiantes afin de modifier la consistance des aliments. Le xanthane est l'un des exopolysaccharides excrétés par divers microorganismes du sol (bactéries notamment). Il joue un rôle important, à l'échelle moléculaire, dans la formation et la conservation des sols3, tout comme le dextrane, le rhamsane ou les succinoglycanes. Rhéologie Viscoélasticité Index. décimale : 668.5 Parfums et cosmétiques Résumé : The purpose of this study was to compare the dynamic (oscillatory) rheological method with a novel texture analysis (TA) method for the assessment of viscoelastic properties of cosmetic semisolids. The instruments used in this study were an air-bearing controlled-stress rheometer (RheoStress RS75, Haake, Germany) and a texture analyser (TA.XT Plus, Stable Micro Systems, UK). The model formulation was a standard semisolid emulsion, containing increasing concentrations of carbomer and xanthan gum, respectively. The rheological methods used were stress sweep (0.5-500 Pa at 1 Hz) and frequency sweep (0.01-10 Hz at 10 Pa). The texture analysis method used was an immersion/de-immersion test with cylindrical probe. The results were analysed for their consistency with theoretical predictions and the presence of any correlations between the methods. The analysis revealed consistent trends related to two novel TA parameters, stringiness (which decreased with the increase in thickener concentration) and resilience (which has shown a mild increasing trend). Elastic modulus G' and viscous modulus G" (both at 1 Hz) were positively correlated to resilience and negatively correlated to stringiness, indicating that those TA parameters reflect the viscoelastic status of the sample. Note de contenu : - Fig. 1. : Visual representation of the oscillatory rheology method and texture analysis method - Fig. 2 : Typical curve obtained by immersion/de-immersion test on texture analyser, expressed as force vs. time - Fig. 3 : Oscillatory stress sweep results for 0.1% carbomer, showing a decrease in the complex modulus (G* - red line) and an increase in the phase angle (δ- green ling) at stress levels above 20 Pa - 4. Elastic moduli for the emulsion samples with increasing carbomer concentrations - Fig. 5 Elastic moduli for the emulsion samples with increasing xanthan gum concentrations - Fig. 6 : Typical curve obtained by immersion/de-immersion test on texture analyser, expressed as force vs. distance. Stringiness is defined as the distance that the product is extended during de-immersion stage before separating from the probe ; a) emulsion with 0.1% carbomer ; b) emulsion with 0.5% carbomer - Fig. 7 : TA graphs of the emulsions with increasing concentrations of carbomer, showing two district areas of the positive curve (A3 and A4), which were used to calculate the parameter resilience, as A4/A3 - Fig. 8. Linear regression fit betwen a TA parameter resilience and two oscillatory parameters, elastic modulus G' and viscousmodulus G", for the series of emulsions with carbomer - Fig. 9. Linear regression fit between a TA parameter stringiness and two oscillatory parameters, elastic modulus G' and viscous modulus G", for the series of emulsions with xanthan gum - Table 1 : The formulation of the semisolid w/o emulsion used in the study - Table 2 : Oscillatory rheology parameters obtained at the frequency of 1 Hz for the emulsion samples stabilised with carbomer and xanthan gum. All values represent the mean of 3 measurements, with the coefficient of variation below 5% - Table 3 : Texture analysis parameters of the emulsion samples stabilised with carbomer and xanthan gum En ligne : https://drive.google.com/file/d/1NLvR09lbNA2cns_g14Lir8nIUd_pZSno/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=30738 [article]

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