Modulus changes

Master curves can also be constmcted for crystalline polymers, but the shift factor is usually not the same as the one calculated from the WLF equation. An additional vertical shift factor is usually required. This factor is a function of temperature, partly because the modulus changes as the degree of crystaHiuity changes with temperature. Because crystaHiuity is dependent on aging and thermal history, vertical factors and crystalline polymer master curves tend to have poor reproducibiUty. 

FIG. 28-19 Equipment for measuring internal friction (modulus) changes during in situ tensile exposure of a metal in a corrosive environment. 

Where is the ratio of the irradiated to unirradiated elastic modulus. The dislocation pinning contribution to the modulus change is due to relatively mobile small defects and is thermally annealable at 2000°C. Figure 13 shows the irradiation-induced elastic modulus changes for GraphNOL N3M. The low dose change due to dislocation piiming (dashed line) saturates at a dose <1 dpa. 

Fig. 13. Neutron irradiation-induced Young s modulus changes for GraphNOL N3M at irradiation temperatures of 600 and 875°C [61],...

The problem of concentration dependence of yield stress will be discussed in detail below. Here we only note that (as is shown in Figs 9 and 10) yield stress may change by a few decimal orders while elastic modulus changes only by several in the field of rubbery plateau and, moreover, mainly in the range of high concentrations of a filler. 

At this point both the spectrum of relaxation times and the way they contribute to the modulus change, so that... 

The modulus changes rapidly with temperature and, at 100°C, retention can be in the 32-38% range for two tested grades. 

In this connection, Fig. 2 provides a qualitative illustration for interpreting modulus change of an elastomer upon filler blending 9). A hydrodynamic or strain amplification effect, the existence of filler-elastomer bonds, and the structure of carbon black 10) all play a part in this modulus increase. 

A solution to this problem requires a knowledge of the atom positions in the dislocation core. Using the atom positions in the Peierls dislocation, Pacheco and Mura (1969) estimated the force on a dislocation due to just a single interface. They obtained the increase in shear flow stress, Ate, due to an elastic modulus change across a sharp interface as... 

To illustrate In (Fig. 26) the effects of iodine number and structure on both running temperature and modulus are combined. If structure is held at a constant level and the iodine number is varied, running temperature and modulus change simultaneously. Both running temperature and modulus increase with increased structure. The cross-hatched area in the center of the graph is the specification for a grade of ISAF. This area thus becomes a target area for quality control for a black with the particle size dictated by N-220. 

Orientation decreases electrical dissipation factors in the direction of the orientation, and increase occurs perpendicular to orientation. Since modulus changes in the opposite way, this indicates that polar vibrations along a stretched plastic molecule are decreased, while transverse vibrations between the stretched molecules are increased. 

In the instance that mechanical effects can be adequately treated as purely elastic, the firequency of a SAW device is perturbed by modulus changes according to... 

You will notice that at low frequencies the storage modulus G ifio) is characterized by low values, in fact those characteristic of a rubber. As the frequency increases, this modulus changes in value by several orders of magnitude and levels out at the value characteristic of the glassy state. At each of these extremes the loss modulus is low and the behavior is largely elastic. Clearly, there is a transition that is akin to a 7 and the loss modulus and tan <5 are a maximum in this frequency range. Keep in mind that this is... 

The most commonly used are the measurement of the Vicat softening point (ASTM D1525, DIN 53460, ISO 306) and the deflection temperature under load (DTUL, ASTM D648). Both measurements monitor the modulus change with temperature, and determine an endpoint when a macroscopic change can... 

In a recent study (24), significant increases in the density of HPZ-derived fiber was achieved without changes in weight or composition. The resultant modulus changes are shown in Figure 7. Extrapolation suggests that the predicted modulus for amorphous, fully dense HPZ-derived fiber corresponds to a value of 360 GPa. 

The properties of tridimensional network formed in the poly(vinyl butyral) on irradiation were estimated by means of ultrasonic and thermal methods. It was found, for instance, that the elastic modulus changed over from 3.33x10 dynes cm. 2 to 4.03x10 dynes cm"2 for gel content increase from 0.082 up to 0.923. Simultaneously, the thermal stability of the crosslin-ked polymer rised from 167°C up to 417°C. [ 2]... 

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