Factor mechanical loss

Good wetting is of course not a sufficient criterion for good contact adhesion because it takes no account of the factors that influence the mechanical loss factor, C, in Eq. 8, nor does it account for residual stress development during cure. But aside from these factors, one might inquire into the validity of the correlation between practical contact adhesion and VEa beyond 0° contact angle , i.e. can any distinction be made based on VEa between different adhesives, all of which perfectly wet the adherend ... 

Fig. 4. Effect of nanocomposites on mechanical loss factor tan 8 vs temperature...

FIGURE 28.12 Mechanical loss factor as a function of temperature for the ENR stocks containing various fillers. (From Sihy Varghese, J. and Karger-Kocsis, J., J. Appl. Polym. Sci., 91, 813, 2004.)... 

The electric properties of polymers are also related to their mechanical behavior. The dielectric constant and dielectric loss factor are analogous to the elastic compliance and mechanical loss factor. Electric resistivity is analogous to viscosity. Polar polymers, such as ionomers, possess permanent dipole moments. These polar materials are capable of storing... 

Fig. 2.22. Dependence of the elastic modulus E and the mechanical loss factor 6 on temperature for various polymers. Curves 1 elastomer (statistical copolymer of ethylene and propylene) curves 2 isotactic polypropylene (semicrystalline)...

The corresponding curves for the mechanical loss factor 6 show the following characteristics The transition to the glassy state for elastomers is seen in curve 1 as a characteristic mechanical absorption . On the other hand, two absorption maxima are visible in the curve for the partially crystalline polymer d2. The first one at 10 °C indicates the glass transition, the second one at about 145 °C is coherent with the crystalline melting point. 

Fig. 33a. Storage modulus, E (at 5 Hz), as a function of temperature for drawn and isotropic POM Delrin 500) samples. Numbers on curves refer to deformation ratio b. The mechanical loss factor, tan 6. corresponding to the data of (a)...

Figure 4 shows the TPA results for the bisphenol-A and the bisphenol-S linked polymers cured at 280°C for six days. Both the dynamic shear modulus and the mechanical loss factor are given as a function of temperature from -150°C to about +300°C. During a TPA run, a temperature scan covering the complete glass-to-rubber transition could not be achieved because the sample softened as the glass transition temperature, Tg, was approached. 

Fig. 32. Storage modulus, E, and mechanical loss factor, tan 6, for GM61 polypropylene (M, = 400,000). Frequency 5 Hz X = 15. As-drawn, A after 60 min annealing at 135 °C...

Polymer (specific type) Prestrain (x, y%) Energy density (MJ Actuation pressure (MPa) Thickness strain (-%) Area strain (%) Young s modulus (MPa) Electic field (MV m ) Dielectric constant Dielectric loss factor Mechanical loss factor Coupling efficiency (%) Efficiency (%) Ref. 

Figure 10-26. Mechanical loss factor tan 6 of poly(cyclohexyl methacrylate) as a function of temperature for various frequencies (after J. Heijboer).

A typical example of these measurements is the mechanical loss factor (for definition, see Section 11). Here a loss maximum for poly (cyclohexyl methacrylate) is observed at — 125°C when the frequency is 10 Hz (Figure 10-26). The maximum is shifted to higher temperatures when the frequency is increased. In addition, the reciprocal loss temperature depends linearly on the logarithm of the frequency (Figure 10-27). Studies on different chemical compounds show that this loss maximum is specific to the cyclohexyl group. The values for both poly(cyclohexyl methacrylate) and poly(cyclohexyl... 

Fig. 13 Temperature-dependence of the dynamic shear modulus G and mechanical loss factor d of different groups of plastics [9]...

Vibration forces applying a dynamic stress load to viscoelastic materials results in a phase shift by the phase angle 8 between stress a and elongation e. The tangent of 8 is called the mechanical loss factor d or mechanical damping. Damping is thus a measure of the heat produced by application of dynamic loads as a result of internal friction (dissipatiOTi) (Fig. 24). 

Fig. 24 The temperature-dependent mechanical loss factor d [4] a crystalline k. .. crystalline...

Fig. 25 Mechanical loss factor (qualitative) plotted against temperature...

Characterization by thermal mechanical analysis indicated that the incorporation of the fibers cause a decrease of the mechanical loss factor. This results in better damping capabilities. Scanning electron microscope (SEM) studies of the impact fractured surfaces of the composites with cotton linter showed a debonding cavitation at the matrix fiber interface. 

The tensile and flexural moduli of the reinforced composites are found to be significantly higher in comparison to the virgin PLA resin. The storage and loss moduli of the composites are found to be increased, but the mechanical loss factor decreases. 

Further, a reduction in the mechanical loss factor is effected. In contrast the situation is reverse for the storage and the loss modulus. 

Figure 3.54 Mechanical loss factor d of Celanese Hostaform C 9021 as a function of temperature torsional oscillation test DIN 53 445 [5].

Figure 23.8 (a) Variation of Storage modulus ( ) as a function of temperature (b) Variation of Loss modulus (E") as a function of temperature (c) Variation of tan 8 (mechanical loss factor) as a fimcUon of temperature. 

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