Temperature dependence storage modulus

Figure 2.8 Normalized temperature-dependent storage modulus from different heating rates [3]. (With permission from Elsevier.)...

After the specimen had cooled down from the first nm, a shift in the loss modulus and tan S was observed for the second nm curves, which indicated an increase in the glass-transition temperature, Tg, of about 12 °C (determined by the peak of the tan S curve). The temperature-dependent storage modulus curve from the second run (representing the U-modulus of the material), however, was similar to that of the first run. After the first run, where the material was heated up to temperatures... 

Figure 1. Temperature dependence storage modulus of Ni-P coated composites for different coating time in bending mode...

The glass transition temperature and the temperature-dependent storage modulus (G ) can be measured particularly sensitive with the DMA (Dynamic Mechanical Analysis) in the torsion oscillation test. The evaluation of the glass transition temperature took place in accordance to the method of the half steps level . The measurements were performed at a Rheometric Scientific DMA MK III (-50°C-350 °C). 

Because of the reason mentioned above, scratch patterns formed were observed to depend on velocity, temperature, and storage modulus (107). Temperature and scratch rate also affect the amount of elastic recovery displayed after scratch is formed (96). In addition, the scratch rate effect might be coupled with cone angle effect to complicate the scratch phenomenon (108). 

Several researchers have reported that bundles commonly form in a variety of thin polymer films when they are raster scanned by a sharp, slow-moving tip (8-13). All previously reported studies were performed at room temperature, and the bundles were observed to align perpendicular to the tip trajectory. Elkaakour et al found that the velocity dependence of the repeat distance of the scan-induced features correlates with the frequency-dependent storage modulus (11). 

Figure 6. Dependence of storage modulus for PMMA and EPDM on temperature at a frequency of 1Hz and a strain of 0.1%.

Figure 5. From left to right temperature dependence of the storage modulus at 0.5 Hz, and of the reduced stress, ( 1.03). Key , PDMS-B1 O, PDMS-B2 X, PDMS-B6 A, PDMS-B7.

Generally, the rheology of polymer melts depends strongly on the temperature at which the measurement is carried out. It is well known that for thermorheological simplicity, isotherms of storage modulus (G (co)), loss modulus (G"(complex viscosity (r (co)) can be superimposed by horizontal shifts along the frequency axis ... 

Figure 10.5 Temperature dependence of storage modulus ( ) and mechanical...

Fig. 19 DMA plots of EVA with MWCNT, showing temperature dependence of a storage modulus and b tan 5...

The dynamic mechanical thermal analyzer (DMTA) is an important tool for studying the structure-property relationships in polymer nanocomposites. DMTA essentially probes the relaxations in polymers, thereby providing a method to understand the mechanical behavior and the molecular structure of these materials under various conditions of stress and temperature. The dynamics of polymer chain relaxation or molecular mobility of polymer main chains and side chains is one of the factors that determine the viscoelastic properties of polymeric macromolecules. The temperature dependence of molecular mobility is characterized by different transitions in which a certain mode of chain motion occurs. A reduction of the tan 8 peak height, a shift of the peak position to higher temperatures, an extra hump or peak in the tan 8 curve above the glass transition temperature (Tg), and a relatively high value of the storage modulus often are reported in support of the dispersion process of the layered silicate. 

Dynamic mechanical analysis (DMA) has been carried out to understand the dynamic response of the blend after the addition of clay. The dependency of the storage modulus obtained from oscillatory tension deformation as a function of temperature is given in Fig. 44. All samples show a steep decrease of E over the temperature range T = 50 to 20°C followed by a rubbery plateau (Fig. 44a). The most exciting information, observed in this figure, is the increase of modulus values at room temperature by the addition of clay. The storage modulus increases from 2 MPa to 54 MPa with the addition of only 10 phr clay in the 25 EPDM/75 CR... 

Fig. 22. Temperature dependence of the storage G (gem 2) and of the loss G" (gem 2) modulus for PDEAAm solutions at frequency 1 Hz. From Ilavsky and Hrouz [30]...

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