Interfacial Rheology

09-Interfacial Rheology

Rheometers are typically used for measuring bulk or three-dimensional properties of materials. In many materials, such as pharmaceuticals, foods, personal care products and coatings, there is a two-dimensional liquid/liquid or gas/liquid interface with distinct rheological properties. The patented Double Wall Ring (DWR) system is compatible with the ARES-G2 for quantitative viscosity and viscoelastic information over the widest measurement ranges. The sample is contained in a Delrin trough and the measuring ring is made of platinum-iridium. These materials are selected for their inert chemistry and ease of cleaning. The double wall geometry provides interfacial shear planes on both sides of the geometry surface for higher sensitivity to the monolayer viscoelastic response at liquid-air or liquid-gas interfaces. The Double Wall Ring is capable of truly quantitative viscoelastic parameters because the interface is “pinned” to the diamond-shaped cross-section of the geometry ring. This patented ring (Patent # 7,926,326) has a diameter of 60 mm and was designed for ease-of-use and maximum sensitivity. Surface viscosity measurements can be conducted on surface viscosities as low as 10-5 Pa.s.m without complicated sub-phase corrections. Oscillation measurements are possible over the widest frequency range of any interfacial system.

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