Rubber hysteresis

The effect of the experimental agents on natural rubber hysteresis was determined by measuring tan 5 at 5% strain using an ARES-A Rheometer at 50°C and 15 Hz. Testing results are provided in Table 2. 

The mechanism of adhesion of fully cured rubbers may be different from that of imcured rubbers. The contribution from interdiffusion will be less significant. However, the application of the compound solution and the compound strip may provide some interdiffusion. The contribution to adhesion may arise principally from factors of interfacial surface energy and rubber hysteresis (the percentage energy loss for cycle of deformation). Bonding arises from several kinds of interactions that may be physical/or chemical in nature. 

There is one obvious drawback of high-hysteresis rubber. In normal rolling operation, considerable elastic deformations still take place in the tyre wall, and high-loss tyres will consume fuel and generate considerable heat. The way out is to use a low-loss tyre covered with a high-loss tread - another example of design using composite materials (Fig. 26.9). 

Natural rubber was the only polymer for elastomer production until the advent of synthetics. Natural rubber, however, continues to maintain its competitive edge due mainly to the gain in properties such as high resilience, low hysteresis, low heat buildup, and excellent tack with mechanical properties achieved through the process of vulcanization [114-115]. The industry is said to be self-sufficient with a good technological base and is expected to compete successfully with synthetics because of the edge in properties mentioned above [116,117]. 

L. Mullins, Rupture of rubber. Part 9. Role of hysteresis in the tearing of rubber, Trans. Inst. Rubber Ind.,... 

De Sarkar et al. [52] have reported a series of new TPEs from the blends of hydrogenated SBR and PE. These binary blends are prepared by melt mixing of the components in an internal mixer, such as Brabender Plasticorder. The tensile strength, elongation at break, modulus, set, and hysteresis loss of such TPEs are comparable to conventional rubbers and are excellent. At intermediate blend ratio, the set values show similarity to those typical of TPEs (Table 5.5). 

Roy Choudhury N. and Bhowmick A.K., Hysteresis of thermoplastic mbber vulcanizates, Plast. Rubber Process. Appl., 11, 1989, 185. 

Figure 9.15 shows typical force curves for a chlorobutyl mbber (CUR) and a namral rubber (NR) sample. It is immediately obvious that the CIIR sample is softer and, as expected, shows much greater hysteresis and hence poorer resilience than the NR sample. 

FIGURE 9.15 Typical force curves on (a) chlorobutyl rubber (CIIR) and (b) natural rubber (NR) samples showing much greater hysteresis and hence poorer resibence for the CIER sample. (From Huson, M.G. and Maxwell, J.M., Polym. Test., 25, 2, 2006.)... 

Diene rubbers can be vulcanized by the action of phenolic compounds like phenol-formaldehyde resin (5-10 phr). Resin-cured NR offers good set properties and low hysteresis [54]. 

Mechanism of the Great Hysteresis Energy of Carbon Black-Filled Rubber... 

As is well known, there is a close relation between the input energy at break, Ub and the hysteresis energy at break, Hb, for many kinds of filled and unfilled rubber vulcanizates, given by the following empirical Equation 18.2 ... 

Equation 18.2 reveals the importance of energy dissipation in the fracmre of mbbery materials, that is, the strength of rubbers, whether filled or unfilled, is governed by the hysteresis energy dissipated in deforming the system. 

FIGURE 18.20 Relation between input energy and hysteresis energy at break for HAF carbon-filled and unfilled styrene-butadiene rubber (SBR). (From Payne, A.R., J. Polymer, Sci., 48, 169, 1974.)... 

Hysteresis energy given from the hysteresis loop at break in carbon black-fiUed rubbers includes the apparent hysteresis energy whose fraction is roughly a half of the total one, which results from the buckling of the super-network. 

It is demonstrated in Figure 22.11 that the quasi-static stress-strain cycles at different prestrains of silica-filled rubbers can be well described in the scope of the above-mentioned dynamic flocculation model of stress softening and filler-induced hysteresis up to large strain. Thereby, the size distribution < ( ) has been chosen as an isotropic logarithmic normal distribution (< ( i) = 4> ) = A( 3)) ... 

FIGURE 22.13 Simple analytical model of hysteresis friction of rubber moving over a rough road profile left). Tire on a wet road track, where hysteresis energy losses dominate the traction behavior right). (From Kluppef M. and Heinrich, G., Kautschuk, Gummi, Kunststojfe, 58, 217, 2005. With permission.)... 

In particular it can be shown that the dynamic flocculation model of stress softening and hysteresis fulfils a plausibility criterion, important, e.g., for finite element (FE) apphcations. Accordingly, any deformation mode can be predicted based solely on uniaxial stress-strain measurements, which can be carried out relatively easily. From the simulations of stress-strain cycles at medium and large strain it can be concluded that the model of cluster breakdown and reaggregation for prestrained samples represents a fundamental micromechanical basis for the description of nonlinear viscoelasticity of filler-reinforced rubbers. Thereby, the mechanisms of energy storage and dissipation are traced back to the elastic response of tender but fragile filler clusters [24]. 

Lindley, P.B., Relation between hysteresis and the dynamic crack growth resistance of natural rubber, Int. J. Fract., 9, 449, 1973. 

The incorporation of reinforcing hllers into rubber results in most cases in an increase of the storage and loss moduli, G and G", and an increase in hysteresis, as quantihed by the loss angle 8, where tan 8 is C jG. When properly dispersed and coupled to the mbber matrix via a coupling agent, as represented by a low Payne effect, silica also shows less hysteretic loss at elevated temperatures. 

FIGURE 31.13 (a) Plot showing the stress-strain behavior of various irradiated rubbers, (b) Plot showing the variation of tensile strength and modulus of rubbers irradiated with different doses, (c) Plot showing the variation of hysteresis loss, set, and elongation at break of irradiated fluorocarbon rubbers. (From Banik, I. and Bhowmick, A.K., Radial. Phys. Chem., 54, 135, 1999. With permission.)... 

Wang, M.-J., Effect of Filler-Elastomer Interaction on Hysteresis, Wet Eriction and Abrasion of EiUed Vulcanizates, Paper presented at a meeting of the Rubber Division, ACS, Akron, May 8-10, 2006. 

Ic. The Results of Stress-Temperature Measurements.—Hysteresis in the stress-strain behavior of rubber and rubberlike materials has presented the most serious problem encountered in the execution of otherwise simple experiments on the change of stress in stretched rubber with temperature at constant length (L) or at constant elonga-... 

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