Isochronal complex, temperature

Dynamic Mechanical Properties. Figure 15 shows the temperature dispersion of isochronal complex, dynamic tensile modulus functions at a fixed frequency of 10 Hz for the SBS-PS specimen in unstretched and stretched (330% elongation) states. The two temperature dispersions around — 100° and 90°C in the unstretched state can be assigned to the primary glass-transitions of the polybutadiene and polystyrene domains. In the stretched state, however, these loss peaks are broadened and shifted to around — 80° and 80°C, respectively. In addition, new dispersion, as emphasized by a rapid decrease in E (c 0), appears at around 40°C. The shift of the primary dispersion of polybutadiene matrix toward higher temperature can be explained in terms of decrease of the free volume because of internal stress arisen within the matrix. On the other... 

Figure 15. Temperature dispersion of isochronal complex, dynamic tensile modulus function at a fixed frequency of 10 Hz, observed for the SBS-PS specimen at unstrethed and stretched (330% elongation) states...

The isochrones showing the temperature dependence of the components of the complex relaxation modulus are rather insensitive to the crystallinity... 

The use of this modulus based on the maximum stress in the part should provide a conservative estimate of the time and temperature dependent deflection of the part. When the isochronous stress-strain curve is highly nonlinear or the part geometry is complex, finite-element structural analysis techniques can be used. Then, the complete nonlinear, isochronous stress-strain curve can be used in a nonlinear finite-element analysis or a linear effective modulus can be used in a linear analysis. 

Samouillan et al. (2011) studied the dielectric properties of elastin at different degrees of hydration and specifically at the limit of freezable water apparition. The quantification of freezable water was performed by DSC. Two dielectric techniques were used to explore the dipolar relaxations of hydrated elastin dynamic dielectric spectroscopy (DDS), performed isothermally with the frequency varying from 10 to 3 x 10 Hz, and the TSDC technique, an isochronal spectrometry running at variable temperature, analogous to a low-frequency spectroscopy (10 to 10 Hz). A complex relaxation map was evidenced by the two techniques. Assignments for the different processes can be proposed by the combination of DDS and TSDC experiments and the determination of the activation parameters of the relaxation times. As already observed for globular proteins, the concept of solvent-slaved protein motions was checked for the fibrillar hydrated elastin (Samouillan et al. 2011). 

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