Effective loss tangent

Fig. 3.79. Effective loss tangent versus size parameter computed with the EFMED routine and the Matlab program QCAMIE...

Briefly explain each of the following points Does it make sense that the loss tangent is larger when a condition of poor adhesion exists between the cord and the rubber Is the adhesive effective Is it equally effective for both of the cord materials ... 

For the microwave-assisted experiments, both solvents were replaced by 1,2-dichlorobenzene, as it couples very effectively with microwaves (loss-tangent (tan 5) at 20 °C 1,2-dichlorobenzene 0.280 as compared to 0.101 for chlorobenzene). Diels-Alder reactions of 3-methoxy or 3-phenyl pyrazinones with DMAD were performed at a pre-selected maximum temperature of 200 °C, whereas the intramolecular reaction of alkyne tethered pyrazinone required a higher temperature (220 °C). The yields obtained under microwave irradiation are comparable with those obtained under conventional conditions, while for the dihydrofuropyridinone the yield was improved from... 

Nakao, T., Okano, T. and Asano, I. (1983). Effects of heat treatment on the loss tangent of wood. Mokuzai Gakkaishi, 29(10), 657-662. 

Fig. 15 Effect of different kinds of nanofiller on the dynamic loss tangent of CR vulcanizates with temperature...

The dielectric constant is generally different in the crystalline and amorphous phases. In this case, Xc in Eq. (95) does not mean the volume fraction of the crystalline phase itself. Furthermore, the amorphous phase exhibits dielectric relaxation in the region where the mechanical relaxation occurs. Considering this effect, Xc should be taken as a complex quantity with a negative imaginary part. However, the inequality (100) is valid in so far as the dielectric loss tangent is smaller than the mechanical one. The inequality (101) holds more generally because the effect of dielectric relaxation enhances the positive value of d"jd. ... 

The most straightforward way to measure the effect of low temperatures on recovery is by means of a compression set or tension set test. Tests in compression are favoured and a method has been standardised internationally. The procedure is essentially the same as set measurements at normal or elevated temperatures and has been discussed in Chapter 10, Section 3.1. As the recovery of the rubber becomes more sluggish with reduction of temperature the dynamic loss tangent becomes larger and the resilience lower (see Chapter 9), and these parameters are sensitive measures of the effects of low temperatures. Procedures have not been standardized, but rebound resilience tests are inherently simple and quite commonly carried out as a function of temperature. It is found that resilience becomes a minimum when the rubber is in its most leathery state and rises again as the rubber becomes hard and brittle. 

Calculate the effective permeability and loss tangent of the ferrite and the e.m.f. when a 0.1 mm gap is introduced into the toroid. 

For a homogeneous dielectric medium, in the absence of interface effects (see Sect. 3.2), the experimental quantities sx and e" are equal to the bulk properties e and e", and the experimental loss tangent becomes... 

The first attempt to use these ideas in epoxy cure was by Fisch and Hofmann 66), but their assignment of permittivity changes to changes in polar group concentrations was marred by what we interpret as electrode polarization effects. Blyakhman et al. 51 52), examined the post-cure dielectric permittivity and loss tangent of anhydride-... 

The heating effect relies upon dielectric polarization [1], itself containing components of electronic, atomic, dipolar, and interfacial polarization, of which the last two have timescales which allow them to contribute to the overall heating effect at these frequencies. The loss tangent, tan 5, consists of two components, s, the dielectric constant, and s", the dielectric loss, where... 

Fig. 37. Effect of annealing on loss tangent (tan 5) of mixtures of stereoregular poly(inethyl methacrylate) (EMMA)3075. (1) [iso-PMMA]/[synd-PMMA] = 1/4, before annealing (2) [iso-PMMA]/[synd-PMMA] = 1/4, after annealing at 140° for 120 h. (3) [iso-PMMA]/[synd-PMMA] = 3/2, before annealing (4) [iso-PMMA]/[synd-PMMA] = 3/2, after annealing at 140° for 120 h. (5) [iso-PMMA]/[synd-PMMA] = 2/3, before annealing (6) [iso-PMMA]/[synd-PMMA] = 2/3, after annealing at 140° for 120 h. (7) [iso-PMMA]/[synd-PMMA] = 4/1, before annealing (8) [iso-PMMA]/[synd-PMMA] = 4/1, after annealing at 140° for 120 h...

Figure 9. Effect of hard-segment content on storage modulus and loss tangent of compression-molded FTMO/FTMT-segmented copolymers...

Figure 5 Effects of wood-polymer composite treatment on relationship between logarithm of E /y and logarithm of tan 5. (A, A) Experimental values of untreated and treated specimens. Dotted line represents experimental correlation line for untreated specimens. Various values of polymer rigidity ( p) and loss tangent (tan 8p) were simulated (curves a to 0-...

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