Elastic properties terms Links

However some non-rubber compounds are also called elastomers if they exhibit a nondeforming elastic property similar to rubber at room temperature, even if the compound is relatively hard. The two main groups of non-rubber elastomers are thermoplastics, e.g., polyvinyl chloride, polypropylene and thermosets, e.g., ethylene propylene rubber, cross-linked polyethylene. These two groups are also covered by the term plastic . 

Elastomer is a general term used for cross-linked polymeric materials such as rubber with elastic properties described above. However, elastomers are not purely elastic materials and they exhibit damping, that is, fractional energy loss per cycle in, say, an oscillatory experiment. The energy loss is due primarily to stress relaxation (viscous dissipation) of inelastic pendant chains and unentangled loops in the network. In the case of a prescribed stress sinusoidal deformation, the applied stress is expressed as... 

What we would like to do is use these thermodynamic properties to calculate an equilibrium elastic moduli. The bulk modulus is by definition the constant of proportionality that links the infinitesimal pressure change resulting from a fractional change in volume (Section 2.2.1). In colloidal terms this becomes... 

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