Viscoelastic and Deformation Characteristics of Structurally Different Commercial Topical Systems

Abstract

Rheological characteristics and shear response have potential implication in defining the pharmaceutical equivalence, therapeutic equivalence, and perceptive equivalence of commercial topical products. Three creams (C1 and C3 as oil-in-water and C2 as water-in-oil emulsions), and two gels (G1 and G2 carbomer-based) were characterized using the dynamic range of controlled shear in steady-state flow and oscillatory modes. All products, other than C3, met the Critical Quality Attribute criteria for high zero-shear viscosity (η0) of 2.6 × 104 to 1.5 × 105 Pa∙s and yield stress (τ0) of 55 to 277 Pa. C3 exhibited a smaller linear viscoelastic region and lower η0 (2547 Pa∙s) and τ0 (2 Pa), consistent with lotion-like behavior. All dose forms showed viscoelastic solid behavior having a storage modulus (G′) higher than the loss modulus (G″) in the linear viscoelastic region. However, the transition of G′ > G″ to G″ > G′ during the continual strain increment was more rapid for the creams, elucidating a relatively brittle deformation, whereas these transitions in gels were more prolonged, consistent with a gradual disentanglement of the polymer network. In conclusion, these analyses not only ensure quality and stability, but also enable the microstructure to be characterized as being flexible (gels) or inelastic (creams).

Effect of Potato Starch Hydrogel:Glycerol Monostearate Oleogel Ratio on the Physico-Rheological Properties of Bigels

“…The amplitude sweep allows for the identification of the linear viscoelastic region (LVR), which corresponds to a region where the sample does not show a structural breakdown under the application of mechanical forces [ 46 ]. Figure 6 shows the amplitude sweeps of all BG and individual gels (O and H).…”

Pectin from Fruit and Berry Juice Production By-Products, Determination of Physicochemical, Antioxidant and Rheological Properties

“…Modulus or elasticity of gels from BPP remain more elastic, moreover, the gel from Red Currant BPP was of the highest elasticity (Figure 6a). The ratio G'/G" determines the condition for weak and strong gels [51]. With the increase of angular frequencyshear strain, the damping factors -loss factors of all pectin gel samples increased (Figure 8), therefore, indicating that gels would change to liquid (damping factor >1) when higher angular frequency was applied.…”

“…Rheological properties of gels from pectin were determined with Anton Paar Modular Compact Rheometer, Smart Pave 102, Germany. 𝐺𝐺′ (the storage modulus -the elastic component of the material) and 𝐺𝐺′′ (the loss modulus), the viscosity 𝜂𝜂, loss factor, tan(𝛿𝛿) = 𝐺𝐺′′/ 𝐺𝐺′ were determined with shear rate from 0.1 to 100 s −1 at 25 °C [51], [52]. Apple pectin (Merk, Sigma Aldrich, Germany) was used to compare physical, chemical and rheological properties.…”

“…Low DE pectin could also affect the viscosity of pectin solutions in further usage and pectin with lower DE could create a better condition for forming gels. Higher viscosity of pectin gels may be as a result of smaller particles of solid fraction [51], [57], [60][30].…”

“…The G′/ G″ values of pectin solutions were almost similar to those of Sigma Aldrich Apple Pectin. A loss factor of 1 means the substance is at a transition between a liquid and a solid state, respectively, the gel point [51], [61]. The increased or decreased equivalent weight (EW), probably might depend from the number of free acids, the lower equivalent weight could be of partial degradation of pectin.…”