Analysis storage modulus

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

Adsorption of rubber over the nanosilica particles alters the viscoelastic responses. Analysis of dynamic mechanical properties therefore provides a direct clue of the mbber-silica interaction. Figure 3.22 shows the variation in storage modulus (log scale) and tan 8 against temperature for ACM-silica, ENR-silica, and in situ acrylic copolymer and terpolymer-silica hybrid nanocomposites. 

Thermodynamic Analysis. As reported previously, the storage modulus G of PDMS networks with tetrafunctional crosslinks is independent of frequency between 10 3 and 1 Hz (21). This behaviour which is entirely different from that of vulcanized natural rubber or synthetic polyisoprene networks, was attributed to the lack of entanglements, both trapped and untrapped, in these PDMS networks. Figure 4 shows that G of a network with comb-like crosslinks is also frequency independent within an error of 0.5%. For comparison, two curves for PDMS having tetrafunctional crosslinks are also shown. The flat curves imply that slower relaxations are highly unlikely. Hence a thermodynamic analysis of the G data below 1 Hz can be made as they equal equilibrium moduli. 

Bauer, Denneler, and Wilert-Porada also studied the influence of temperature (30-120°C) and humidity (0 - 100%) on the mechanical properties of Nation 117 membrane via dynamic mechanical analysis (DMA). The mechanical behavior of Nation membranes in a humid atmosphere was observed to differ significantly from that in dry atmosphere, and the influence of water on the mechanical properties of the acid form of Nation was found to be complex. The maximum of the storage modulus ( ) as a function of humidity was shifted to higher humidity values with increasing temperature. 

In analysis of the dynamic storage modulus, toluene diamine-cured resins schibited the highest modulus in standard-cured san les, vAiereas all the HT-cured resins showed nearly similar elastic moduli. 

Fig. 4 DMTA analysis of a PPC with a Mn of 46 kDa, showing storage modulus G, loss modulus G", and tan d as a function of temperature (Borchardt and Luinstra, unpublished data)...

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... 

Most of the physical properties of the polymer (heat capacity, expansion coefficient, storage modulus, gas permeability, refractive index, etc.) undergo a discontinuous variation at the glass transition. The most frequently used methods to determine Tg are differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and dynamic mechanical thermal analysis (DMTA). But several other techniques may be also employed, such as the measurement of the complex dielectric permittivity as a function of temperature. The shape of variation of corresponding properties is shown in Fig. 4.1. 

Figure 10.2 The relaxation rate (1/T2s)max measured for a cured mixture of a poly(ethylene glycol) diacrylate (Mn = 700 g/mol) and 2-ethylhexyl acrylate as a function of the storage modulus at 273 K (-0.1 °C) [52]. The rubbery plateau was observed for all samples at 273 K (-0.1 °C). (1/T2s)max corresponds to the relaxation component with short decay time that was measured at 323 K (50 °C) for partially swollen in 1,1,2,2-C2D2C14 samples. This relaxation component corresponds to the relaxation of network chains. The line represents the result of a linear regression analysis intercept = 1.1 0.3 ms-1 slope = 0.34 0.02 ms MPa)"1. The correlation...

The storage modulus, E, is obtained by dynamic mechanical thermal analysis and as the temperature is increased, the stiffness of both materials is seen to fall. In the region 120-160 °C, however, PEN is significantly stiffer and stronger, with a modulus almost twice that of PET. 

Fig. 15. Dynamic mechanical analysis of 100 minutes-aged Thornel 300/Fiberite 934 composite showing the loss tangent and the dynamic storage modulus...

TABLE 2. Thermal aging stability and storage modulus analysis of laminates coated with selected experimental agents using PMMA or PC as the coating substrate. 

Dynamic thermal mechanical analysis indicates significant broadening of glass transition temperature at or around PU/EP composition of 70/30. This is true for all three groups studied. At this composition, storage modulus showed much less steep variations with temperature during the transition from glassy to rubbery state. 

DSA analysis of Resin 5208 exhibits two dispersion regions. The first is related to gelation and the second is related to vitrification. The first DSA peak occurs on the attainment of a value for the resin storage modulus slightly lower than that of the rubbery plateau. The first TBA peak occurs at the point where the composite (braid and resin) attains measurable rigidity. 

---