Rubber stress-strain diagram

Fig. 5 Stress-strain diagram of rubber composite mixed at different temperatures containing 5 phr organoclay in a XNBR matrix. Circles indicate crossover points...

Fig. 13 Variation of 200% modulus (a), tensile strength (b), and elongation at break (c) with the amount of organoclay and XNBR. Stress-strain diagram of the organoclay-rubber composites (d)...

Nonmetallic substances show a wide variety of stress-strain diagrams, with each type related to the bonding of the particular material. One type, that for an elastomeric rubber, is shown in Fig. 12. Compared to a metal, the rubber can support much larger strains and only much smaller stresses. It follows Hook s law only as a limit at very small displacements. However, displacement is elastic well outside of this range. 

Figure 11-15. Stress/strain diagram of a natural rubber (above) and an it-poly(styrene) (below) at room temperature. Left experimental curves right true stress curves. Numerical values were not given for the lower left figure in the original work. (After P. I. Vincent.)...

Fig. 104. Stress strain diagrams of (a) swollen isotropic cellulose filaments and (b) of moderately vulcanized rubber at loading and unloading (stress on actual cross-section)...

This can be followed by considering the changes in the stress-strain diagram (Fig. 5). The material, tested immediately after being prepared at 250° C, is rather stiff on applying a stress of 40 kg/cm it shows an extension of only about 150%, whereas for the 350 C material this value is 500%. The stress-strain curve for the last-mentioned material shows a close resemblance to that for raw rubber, as appears by comparison with the dotted line in Fig. 5b. Upon storing, the highly elastic sulphur becomes stiffer. 

Influence of vulcanisation on the stress-strain diagram of rubber. 

Of fundamental importance is the fact that it has proved possible to calculate the stress-strain diagram for a material like rubber starting from some simple assumptions concerning the free rotation, and flexibility of the coiled molecules. Thus, Guth and James derived the formula ... 

The production of crystals in a polymer by the action of stress, usually in the form of an elongation. It occurs in fiber spinning, or during rubber elongation, and is responsible for enhanced mechanical properties. Simultaneous readings of load and deformation, converted to stress and strain, plotted as ordinates and abscissas, respectively, to obtain a stress-strain diagram. 

Plastic deformation n. (1) A change in dimensions of an object under load that is not recovered when the load is removed. For example, squeezing a chunk of putty results in plastic deformation. The opposite of plastic deformation is elastic deformation, in which the dimensions return instantly to the original values when the load is removed, e.g., as when a rubber band is stretched and released. (2) In tough plastics, deformation beyond the yield point, appearing on the stress-strain diagram as a large extension with httle or no rise in stress. A part of the plastic deformation may be recovered when the stress is released the remainder is plastic flow. 

The Vc and Me values for crosslinked polymer networks can also be evaluated from stress-strain diagrams on the basis of theories for the rubber elasticity of polymeric networks. In the relaxed state the polymer chains of an elastomer form random coils. On extension, the chains are stretched out, and their conformational entropy is reduced. When the stress is released, this reduced entropy makes the long polymer chains snap back into their original positions entropy elasticity). Classical statistical models of entropy elasticity affine or phantom network model [39]) derive the following simple relation for the experimentally measured stress cr ... 

Stress-strain diagrams of various crosslinked rubbers (a) sulfur-crosslinked natural rubber (100% 1,4-cis-polyisoprene) at 300 K, (b) sulfur-crosslinked natural rubber at 343 K, (c) radiation-crosslinked synthetic polyisoprene (93% l,4-cis-isomer) at 300 K (see text)... 

Tensile stress-strain tests with amorphous rubbers over a range of strain rates and temperatures have shown that for a given rubber the failure point lay along an envelope of the stress-strain diagram (Smith, 1962) (Fig. 4.8) and that the data could be superimposed by a WLF-type shift operation (Fig. 4.9). 

The area under a reversible stress-strain diagram represents the energy stored per unit volume. How much work is done on an ideal rubber band that is slowly and reversibly stretched to a = 2.00 The initial slope of the stress-strain curve is known to be 2 MPa, and the volume of the rubber band is 4.0 cm. ... 

FIGURE 10.7 Typical stress-strain diagrams for brittle glass (A), resilient rubber (B), and ductile plastic (C). 

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