Dynamic moduli scaling parameters

The first involves a study by Malysa et al. [5] of the surface elasticity and dynamic stability of wet foams for a homologous series n-alcohols (C4-Cxo). On ascending the series, the authors found that foam stability passed through a maximum with the Cg-Cg alcohols. This effect was found to be unrelated to the Marangoni dilational modulus. However, the authors also determined a parameter they called the effective elasticity which depended on the kinetics of adsorption. They foimd that at short time scales (0.05-0.10 s), the effective elasticity correlated well with foam stability, reaching a maximum value with the C7 alcohol. 

Mechanical Load. Static mechanical load by strain leads to stretching of random-coil polymer chains in the direction of sample elongation and chain compression in the orthogonal directions. The value of the residual dipolar and quadrupolar couplings is increased by the mechanical load, and moreover, the distribution of the correlation times is also modifled. Therefore, many NMR parameters sensitive to the residual dipolar couplings and slow motions can be used for characterization of the local strain-stress effects in heterogeneous elastomers (158,160,161,179). Dynamics mechanical load leads to sample heating where the temperature distribution in dynamic equilibrium is determined by the temperature-dependent loss-modulus and the thermal conductivity of the sample. Because transverse relaxation rate (approximated by the T2 relaxation) scales with the temperature for carbon fllled SBR, a T2 map provides a temperature map of the sample. Such temperature maps have been measured for carbon-black filled SBR cylinders for different filler contents and mechanical load (180). 

The transverse relaxation time strongly depends on temperature (cf Fig. 37a), so that the temperature can be mapped by parameter imaging of T2. Axial parameter projections have been acquired in dynamic equilibrium at a shear rate of 10 Hz and for carbon-black contents ranging from 10 to 70 phr. Onedimensional cross sections through those projections are depicted in Figure 37b. An increase of the temperature in the center of the sample is observed with increasing carbon-black contents which scales with the increasing loss modulus of... 

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