Surface rheology, definition

The lUPAC recommendation Manual of Symbols and Terminology for Physicochemical Quantities and Units Appendix II Definitions Terminology and Symbols in Colloid and Surface Chemistry, Part 1.13 Selected Definitions, Terminology and Symbols for Rheological Properties, Pure Appl. Chem. 51 (1979) 1213 also contains recommendations for surface rheology. Only part of them are heeded in this chapter. 

M. van den Tempel. Surface Rheology, in Journal of Non-Newtonian Fluid Mechanics 2 (1977) 205-19. (Review with a phenomenological emphasis operational definitions and coupling to bulk rheology.)... 

A third definition of surface mobility is essentially a rheological one it represents the extension to films of the criteria we use for bulk phases and, of course, it is the basis for distinguishing states of films on liquid substrates. Thus as discussed in Chapter IV, solid films should be ordered and should show elastic and yield point behavior liquid films should be coherent and show viscous flow gaseous films should be in rapid equilibrium with all parts of the surface. 

De Man (1983) has reviewed this property of fats. Consistency is defined as (1) an ill-defined and subjectively assessable characteristic of a material that depends on the complex stress-flow relation or as (2) the property by which a material resists change of shape. Spreadabil-ity, a term used in relation to consistency, is the force required to spread the fat with a knife. The definition is similar to that for hardness the resistance of the surface of a body to deformation. The most widely used simple compression test in North America is the cone penetrometer method (AOCS Method Cc 16-60, 1960). More sophisticated rheological procedures are also available. Efforts have been made to calibrate instrumental tests with sensory response. With the cone penetrometer method, penetration depth is used as a measure of firmness. Hayakawa and De Man (1982) studied the hardness of fractions obtained by crystallization of milk fat. Hardness values obtained with a constant speed penetrometer reflected trends in their TG composition and solid fat content. 

The sol-gel blend or pre-crosslinked grades of polychloroprene such as the T Type polychloroprenes available from DuPont Dow contain a highly cross-linked network, which that acts as an internal processing aid (94,95). The hlend has many of the same characteristics as the sol component, hut different compoimd rheology properties. This composition results in faster extrusion with extrudates having smoother surfaces. Extrudates also retain their shape better with good definition until vulcanized. 

Rheological properties of formed surface layers can be considered as the strong demonstration of protein adsorption at a/w surface. These properties show the formation of a surface film of definite structure, that can be regarded as a thin layer of a third phase [36]. 

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