Rubber, viscoelastic behavior elastomers

The surface forces, of van der Waals type for rubber-like materials, are able to grandly modify the stress tensor provided by the contact of a blunt asperity applied against the flat and smooth surface of a rubber sample. It will be shown how the coupling of surface adhesion properties and bulk viscoelastic behavior of rubber-like material allows us to solve adherence problems. This will be illustrated through three examples the spontaneous peeling due to the intervention of internal stresses the no-rebound of balls on the smooth surfoce of a soft elastomer and the adhesive contact and rolling of a rigid cylinder under a smooth-surfaced sheet of rubber. 

The addition of iso-dimensional nanofillers into elastomers causes many changes in mechanical and physical properties, but especially, the effect of nanoparticles on the nonlinear viscoelasticity properties of rubbers has been investigated. In rubber matrices containing nanofillers, exhibition of the Payne effect is strongly connected with the dispersion of the nanofiller and the tendency to create aggregates among the nanoparticles. Filler dispersion plays an important role in determining the nonlinear viscoelastic behavior of these systems— in particular, both the properties of the filler particles and filler-polymer compatibility. 

The nonlinear viscoelastic behavior of elastomers is usually related to their inner structure interaction, namely, the interaction between the matrix molecules, the interaction between the matrix molecules and fillers, and the interaction between the fillers. Of course, the effect of characteristics of the inner structure on the nonlinear viscoelastic behavior of elastomers cannot be ignored, since it is also related to portion of the energy dissipated during dynamic deformation. For instance, the filler parameters are important which influence the dynamic properties of rubber compounds, dynamic hysteresis in particular, as well as their temperature... 

Filling an elastomer with short fibers essentially involves combining the viscoelastic behavior of a rubber matrix with the strength and stiffness of the fiber, in order to obtain useful engineering materials. Reinforcing elastomers... 

Abstract This chapter describes the influence of three-dimensional nanofillers used in elastomers on the nonlinear viscoelastic properties. In particular, this part focuses and investigates the most important three-dimensional nanoparticles, which are used to produce rubber nanocomposites. The rheological and the dynamic mechanical properties of elastomeric polymers, reinforced with spherical nanoparticles, like POSS, titanium dioxide and nanosdica, were described. These (3D) nanofillers in are used polymeric matrices, to create new, improved rubber nanocomposites, and these affect many of the system s parameters (mechanical, chemical, physical) in comparison with conventional composites. The distribution of the nanosized fillers and interaction between nanofUler-nanofiUer and nanofiller-matrix, in nanocomposite systems, is crucial for understanding their behavior under dynamic-mechanical conditions. 

Usually, sealants and adhesive materials for construction applications are evaluated by looking at the engineering side, butnotthe chemistry of the material. As a result, only tests that measure the mechanical properties are used. Most of the studies on the viscoelastic properties use traditional tests such as tensile testing to obtain data, which can be used in complicated mathematical equations to obtain information on the viscoelastic properties of a material. For example, Tock and co-workers studied the viscoelastic properties of stmctural silicone rubber sealants. According to the author, the behavior of silicone mbber materials subjected to uniaxial stress fields carmotbe predicted by classical mechanical theory which is based on linear stress-strain relationship. Nor do theories based on ideal elastomers concepts work well when extensions exceed... 

They presented a theoretical approach to predict the behavior of silicone rubber under uniaxial stress. The model is based on the concept of the classical Maxwell treatment of viscoelasticity and stress relaxation behavior, and the Hookean spring component was replaced by an ideal elastomer component. From the test data, the substitution permits the new model estimation of the cross-link density of the silicone elastomer and allows a stress level to be predicted as a complex function of extension, cross-link density, absolute temperature, and relaxation time. Tock and co-workersh" ] found quite good agreementbetweenthe experimental behavior based on the new viscoelastic model. By using dynamic mechanical analysis (DMA), the authors would have been able to obtain similar information on the silicone elastomer. 

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