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Phase Separation in Cosmetic CreamsTemperature stability of materials such as food and cosmeticsis very important for product performance in storage andtransportation. Rheological testing is widely used for stabilityevaluations; however, the ability to simultaneously measuredielectric properties can provide more valuable insight forcomplex formulations. An example is shown in the figure to theright for two water-based cosmetic creams tested by cooling from25 °C down to -30 °C. In comparing only storage modulus, G’,data of the two materials, the POND’S ® cream shows little increasefollowed by a three decade jump at -18 °C, but NIVEA creamexhibits a more continuous change in the modulus over the entiretemperature range. One may conclude from the mechanicalresponse alone that the large jump in G’ of POND’S at -18 °Cis associated with instability. However, having the simultaneousmeasurement of the loss permittivity, ε”, provides informationrelating to the change in ion mobility; primarily of the water phasein these samples. In the ε” the NIVEA shows a two decade jumpcompared to very little change in the ε” of the POND’S. The largeincrease in ε” is due to increased ion mobility in the material as thewater separates. In the final analysis, phase separation occurs inthe NIVEA, not the POND’S. During the cooling process, as phaseseparation gradually occurs, the water phase grows changingthe morphology. As the morphology gradually changes, so toodoes the G’. The large change in G’ of the POND’S is the result ofa transition of a more stable and uniform morphology.Simultaneous Dielectric and Rheology of Hand Creams on FreezingStorage modulus (Pa)10 810 710 610 510 410 3 -40 -30 -20 -10 0 10 20 3010 -130.0ε’Temperature (˚C)POND’S creamNIVEA creamCooling rate: 3 ˚C/minMechanical Frequency: 1 HzDielectric Frequency: 200 HzDielectric Temperature Ramp on PMMA10 710 610 510 410 310 210 110 00.1750.15Loss permittivity ε” (pF/m)Dielectric Temperature Rampat Multiple FrequenciesThe figure to the right shows a temperature ramp on a Poly(methyl methacralyte), PMMA, sample at four different dielectricfrequencies ranging from 1,000 Hz to 1,000,000 Hz. It can beseen here that the magnitude of ε’ decreases with increasingfrequency through the transition region and the peak of theStorage permittivity ε’ (pF/m)15.00-15.01000 Hz10000 Hz100000 Hz1000000 Hztan δ0.1250.10.0750.05tan (δ)transition in tan d moves to higher temperatures with increasing0.025frequency.-30.0025 50 75 100 125 150 175 200 225Temperature (˚C)section Dielectric title 35
interfacial rheologyACCESSORIESInterfacial AccessoriesRheometers are typically used for measuring bulk or threedimensionalproperties of materials. In many materials, suchas pharmaceuticals, foods, personal care products andcoatings, there is a two-dimensional liquid/liquid or gas/liquid interface with distinct rheological properties. Only TAInstruments offers three separate devices for the most flexibilityand widest range of quantitative measurements for thestudy of interfacial rheology. The options include a patentedDouble Wall Ring (DWR) system for quantitative viscosity andviscoelastic information over the widest measurement ranges, aDouble Wall Du Noüy Ring (DDR) for samples available inlimited volumes, and a traditional Bicone for interfacial viscositymeasurements.Interfacial Viscosity (Pa.s.m)10 010 -110 -210 -310 -410 -510 -6BiconeMolecules/nm 2water0.360.91.441.83.67.2Double Wall Du NoüyRing (DDR)surface loading10 -7 10 -4 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3.Shear rate γ (1/s)36ApplicationIn this series of tests, the surfactant SPAN65 was spread evenlyat the water-air interface using a solution of SPAN in chloroform.After the evaporation of the chloroform, the SPAN65 filmdeposited on the water was measured using the Double WallRing Interfacial accessory. Different loadings of surfactant weretested from 0 (just water, no surfactant layer) to 7.2 moleculesper nm 2 . Continuous shear experiments were conducted andthe interfacial viscosity was measured as a function of shearrate and interfacial concentration. As expected, the surfactantlayer shows significant shear thinning. At high rates, thesub-phase contributions dominate for the loadings less than1.8 molecules/nm 2 . Sub-phase correction becomes importantbelow an interfacial viscosity of 10 -5 Pa.s.m and the well-definedgeometry of the DWR makes these quantitative sub-phasecorrections possible. At higher interfacial viscosities, sub-phasecontributions are negligible and the correction is unnecessary.
Page 5 and 6: peltier plateTEMPERATURE SYSTEMSCom
Page 7 and 8: peltier plateTECHNOLOGY80 mm Diamet
Page 9 and 10: peltier plateGEOMETRIESSmart Swap P
Page 11 and 12: peltier plateACCESSORIESWater at 40
Page 13 and 14: upper heated plateTEMPERATURE SYSTE
Page 15 and 16: UHP and ATCTEMPERATURE PERFORMANCES
Page 17 and 18: peltier concentric cylinderTEMPERAT
Page 19 and 20: concentric cylinderACCESSORIES AND
Page 21 and 22: concentric cylinderACCESSORIESTorsi
Page 23 and 24: pressure cellACCESSORYPressure Cell
Page 25 and 26: electrorheologyACCESSORYElectrorheo
Page 27 and 28: 26electrically heated plateTEMPERAT
Page 29 and 30: ETC ovenENVIRONMENTAL TEST CHAMBERE
Page 31 and 32: ETCGEOMETRIESETC Geometry Accessory
Page 33 and 34: ETC and EHPPOLYMER APPLICATIONSThem
Page 35: dielectric measurementACCESSORYBNC
Page 39 and 40: small angle light scatteringACCESSO
Page 41 and 42: UV curingACCESSORIESUV Curing Acces
Page 43 and 44: starch pasting cellACCESSORYLocking
Page 45 and 46: tribo-rheometryACCESSORYTribologyTr
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