Tensile storage modulus curves

Figure 5.37. Tensile storage modulus curves of as-spun and drawn Nylon M5T fibers as a function of temperature (from Menczel et al., 1996, with permission of Springer).

Thermal mechanical analysis (Dupont 990/942 IMA), and dynamic mechanical analysis (Dupont 1090/982 DMA) curves for a designed set of model formulations were evaluated for CTE and tensile storage modulus as a function of filler level and elastomer additive type and level. Fifteen formulations were prepared with 68-75% filler, 0-4% silicone elastomer A, 0-4% non-silicone elastomer B and the balance 17-32%. Both elastomers have Tg s below room temperature. An extreme vertices formulation design was generated by computer (Table I). 

Dynamic mechanical properties exhibit side chain or branch motions short main chain segment motions, main chain segmental motions, recrystallization, and melting. These transitions are observed as inflections in the storage modulus curve with temperature, peaks in either the loss modulus or damping factor (tan( )) curves. Figure 3.11 shows the dynamic mechanical spectroscopy (DMS) of a ZN-VLDPE at 1 Hz in tensile mode. The glass transition temperature (maxima of the loss modulus... 

The hot-stretching was performed at the temperature where the tensile storage modulus at 10 Hz was 10 MPa [212°C]. The stress-strain curve at a strain rate of 0.05 s is shown in Fig. 9.21. The curve is a typical one for a viscoelastic body in a rubbery region. 

Figure 2.17. Typical DMA curves of polyurethane elastomers tensile storage modulus, E, (left) and loss tangent, tan 6 = E"/E, (right). Measurements were performed at a frequency of 1 s The PEUU curves are typical for weakly phase-segregated elastomer, while PEU curves are typical for strongly phase-separated elastomer with percolated hard phase [27]...

As one example, in thin films of Na or K salts of PS-based ionomers cast from a nonpolar solvent, THF, shear deformation is only present when the ion content is near to or above the critical ion content of about 6 mol% and the TEM scan of Fig. 3, for a sample of 8.2 mol% demonstrates this but, for a THF-cast sample of a divalent Ca-salt of an SPS ionomer, having only an ion content of 4.1 mol%, both shear deformation zones and crazes are developed upon tensile straining in contrast to only crazing for the monovalent K-salt. This is evident from the TEM scans of Fig. 5. For the Ca-salt, one sees both an unfibrillated shear deformation zone, and, within this zone, a typical fibrillated craze. The Ca-salt also develops a much more extended rubbery plateau region than Na or K salts in storage modulus versus temperature curves and this is another indication that a stronger and more stable ionic network is present when divalent ions replace monovalent ones. Still another indication that the presence of divalent counterions can enhance mechanical properties comes from... 

Storage modulus measurements. All measurements were taken at temperatures near 45 °C above the network Tg s. Representative network true stress versus strain curves from the tensile experiments are shown in Fig. 2. The ordinate axis, true stress, is normalized by 3eRT to account for the different test temperatures employed. The resultant curves are thereby directly comparable for structural differences, since the instantaneous slopes are proportional to l/M, after Eq. (2). The curves of all five networks are linear and reversible up to strains of around 10 percent. The reversibility suggests that the measurements were performed under near-equilibrium conditions and that the networks were stable at the high test temperatures employed. 

Tensile measurements were taken in most cases to determine the mechanical properties of NR/CNT nanocomposites. Initial modulus, determined from stress-strain curves, was observed to remarkably increase with the filler content. At 1 wt%, the increase was 25.9%, compared to pure NR, ° at 3, 5, 7 and 10 wt% the increase % was 142, 306, 680 and 850, respectively.It was commented that the modulus increase is due to the hydrodynamic effect, further increased by the filler anisotropy, and by the presence of occluded rub-ber.i° For composites with 37 wt% of CNT, the storage modulus was about three orders of magnitude higher than that of the pure rubber. CNT modification with resorcinol caused an increase in modulus at all CNT loadings, indicating improved filler-matrix adhesion. 

---