Storage modulus and mechanical

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

Figure 5.31. Effect of absorbed H2O on the storage modulus and mechanical damping behavior (g" or tan 5) of poly(ether sulfone) at IHz curves (a) 0.31% H2O, curve (b) 0.07% H2O the P relaxation in this polysulfone is dependent on the water content of the samples as illustrated the relaxation intensity increases with the amount of moisture present. [From AUen et al. (1971) reprinted with permission of Elsevier.]...

Figure 6 Typical plots from dynamic mechanical thermal analysis showing storage modulus and tan6 variation with temperature [27]. SO (---), S2 (--).

A technique for performing dynamic mechanical measurements in which the sample is oscillated mechanically at a fixed frequency. Storage modulus and damping are calculated from the applied strain and the resultant stress and shift in phase angle. 

Figure 3. Dynamic mechanical spectra of TEOS-PDMS materials made with 48 wt% TEOS (PDMS MW = 1700), storage modulus and tank...

Figure 7. Effect of TEOS content on the dynamic mechanical behavior of TEOS-PTMO materials (PTMO MW=2000), (a) storage modulus and (b) tanS.

The dynamic mechanical property data for Groups 1,2,and 3 materials were obtained from a Polymer Laboratory Model 983 Dynamic Mechanical Thermal Analyzer (DMTA), and include log tan S (loss factor), log E (storage modulus), and log E (loss modulus). Frequency was held constant at 10 Hz for all samples. The superposed results are shown for each group in Figures 2-10. 

Another possibility of determining the gel point with the help of rheological methods is dynamical mechanical spectroscopy. Analysis of change of dynamic mechanical properties of reactive systems shows that the gel point time may be reached when tan S or loss modulus G" pass a miximum [3,4,13], Some authors proposed to correlate the gel point with the intersection point of the curves of storage and loss moduli, i.e., with the moment at which tan 5 = 1 [14-16], However, theoretical calculations have shown that the intersection point of storage modulus and loss modulus meets the gelation conditions only for a certain law of relaxation behavior of the material and the coincidence erf the moment of equality G = G" with the gel point is a particular case [17]. The variation of the viscosity... 

Using a computerized data reduction scheme that incorporates a generalized WLF equation, dynamic mechanical data for two different polymers were correlated on master curves. The data then were related to the vibration damping behavior of each material over a broad range of frequencies and temperatures. The master curves are represented on a novel reduced temperature nomograph which presents the storage modulus and loss tangent plots simultaneously as functions of frequency and temperature. ... 

Tensile properties were measured by using Shimadzu mechanical tester DSS5000. The cross head speed was 2 mm/min. Viscoelastic properties(tensile storage modulus and tan S) were measured by a tensile type dynamic mechanical analysis(SEIKO Instrument DMS 200). The... 

These equations are often used in terms of complex variables such as the complex dynamic modulus, E = E + E", where E is called the storage modulus and is related to the amount of energy stored by the viscoelastic sample. E" is termed the loss modulus, which is a measure of the energy dissipated because of the internal friction of the polymer chains, commonly as heat due to the sinusoidal stress or strain applied to the material. The ratio between E lE" is called tan 5 and is a measure of the damping of the material. The Maxwell mechanical model provides a useful representation of the expected behavior of a polymer however, because of the large distribution of molecular weights in the polymer chains, it is necessary to combine several Maxwell elements in parallel to obtain a representation that better approximates the true polymer viscoelastic behavior. Thus, the combination of Maxwell elements in parallel at a fixed strain will produce a time-dependent stress that is the sum of all the elements ... 

Rheovibron (dynamic) viscometer is widely used for measurements of dynamic mechanical properties such as loss modulus, storage modulus, and dissipation factor, each as a function of temperature. In this instrument, the test specimen is clamped between strain gauges and subjected to low order of sinusoidal strain at a specified frequency. The value of tan d is directly read and the storage and loss moduli are calculated using sample dimensions and instrument readings. 

Figure 25 Typical transition behavior in mechanical storage modulus and damping for a semicrystalline polymer. Relaxations in the amorphous phase are labeled with Greek letters (a, p, 7) with... 

FIGURE 13.24 (a) The dynamic mechanical spectrum for polyfethylene terephthalate) (PET) showing the storage modulus and tan 5 as a function of temperature, (b) The dielectric (storage and tan 5) behavior for PET in comparison with the mechanical response. (From Wetton, R.E. et al.. Inti. Lab., March, 1986. Figure 13a and Figure 13b, p. 60. With permission from International Laboratory.)... 

Figure 7.1 Dynamic mechanical spectra showing the variation of storage modulus ( ) and loss modulus ( ") with temperature for copolymers prepared by emulsion copolymerization of vinyl acetate (71 mol%) with n-butyl acrylate (29 mol%) using (i) a batch process (T, E V, E"), and (ii) a semi-batch process operated under monomer-starved conditions ( , " o, "). (Adapted from ref. 1.)...

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