ELASTOMERS

Elastomers, or rubber like materials, have many engineering applications due to their wide availability and low cost. They are also used because of their excellent damping and energy absorption characteristics, flexibility, resiliency, long service life, ability to seal against moisture, heat, and pressure, and non-toxic. It can be easily molded into almost any shape. Applications of elastomers include solid propellant, biomechanics and medical/dental, tires, gaskets, and engine mounts.

Elastomers are very unique material. During processing and shaping, it behaves mostly like a highly viscous fluid. After its polymer chains have been cross-linked, by vulcanization (or by curing), elastomers can undergo large reversible elastic deformations. Unless damage occurs, it will return to its original shape after removal of the load.

The unique properties of elastomers are such that:

1.      It can undergo large deformations under load, sustaining strains of up   to 500 percent in engineering applications.

2.      Its load-extension behavior is markedly nonlinear.

3.      Because it is visco-elastic, it exhibits significant damping properties. Its behavior is time and temperature-dependent.

4.      It is nearly incompressible. This means its volume does not change appreciably with stress.

Fillers are usually added (dispersed in a network of polymeric chains) to elastomers to enhance their mechanical properties, e.g. fillers are added to rubber products such as car tires and shock mounts to enhance their stiffness and toughness properties.

 The most commonly used fillers are: carbon black and silica. The carbon particles range in size from a few hundred to thousands of angstroms. They influence the dynamic and damping behavior of rubber in a very complex and non-proportional manner. The unique behavior of carbon black-filled elastomers results due to a rigid, particulate phase and the interaction of the elastomer chains with this phase