Deformations during processing

E Is heat simultaneously applied to the part to be deformed during processing (5) ... 

Nerve - The elastic resistance of raw rubber or compounds to permanent deformation during processing. A nervy tank lining will be difficult to lay around tight bends or in corners because of springback. 

When rubber is deformed during processing operations such as extrusion or calendaring, its inherent elasticity will cause some subsequent recovery. A fundamental material constant characterizing this tendency is, defined in Eqs. (6.12) and (6.14). Elastic recovery is also reflected in die swell, D, defined as the ratio of the flnal and initial dimensions perpendicular to the flow. Die swell is governed by the normal force, although predictions of D for an arbitrary deformation are not possible. However, for steady-state flow there are approximate relations between D and the first (primary) normal force (Tanner, 1970),... 

The most significant deformations during processing are extensional and simple shear flows at high strain rate. Stretching, or irrotational, flows are... 

Small as well as long polymer molecules exhibit different refractive indices parallel and perpendicular to the molecular chain axis. Thus, all polymers should be viewed as intrinsically anisotropic. The degree of anisotropy exhibited in bulk property behavior will depend on the molecular orientation imposed by deformation during processing or testing. Only in its unoriented state can a polymer be... 

The fact that shock waves continue to steepen until dissipative mechanisms take over means that entropy is generated by the conversion of mechanical energy to heat, so the process is irreversible. By contrast, in a fluid, rarefactions do not usually involve significant energy dissipation, so they can be regarded as reversible, or isentropic, processes. There are circumstances, however, such as in materials with elastic-plastic response, in which plastic deformation during the release process dissipates energy in an irreversible fashion, and the expansion wave is therefore not isentropic. 

In the continuous chain model, a large part of the deformation during extension of the fibre consists of the shear deformation as a result of which the chain orientation distribution contracts. This leads to the concave shape of the tensile curve, often found for polymer fibres. Therefore, this description of the extension of the fibre implies a strain hardening process. 

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