Elastomers and rubber shapes are natural or synthetic  polymers that exhibit elastic properties and can be formed into finished or semi-finished stock.  These amorphous polymers are usually thermosets, but are also available as thermoplastics. Elastic polymer (elastomer) and  rubber shapes are available in different forms and sizes, and often use filler materials. The chemical system , filler material, and other characteristics of these products determine their thermal, mechanical, electrical and optical properties.

Thermoset Elastomers vs. Thermoplastic Elastomers (TPE)

Elastomers and rubber shapes may be divided into thermosets and thermoplastics.

Thermosetting elastomers are subjected to heat and pressure (vulcanization) to impart strength. This process causes permanent crosslinking and imparts high elastic properties.  Cured thermosets generally have higher resistance to heat than thermoplastics, but cannot be reprocessed through melting. Often, thermoset elastomers are used in fluid sealing applications.

Thermoplastic elastomers (TPE) are processed through blow, extrusion, or injection molding instead of vulcanization. These products are relatively expensive, but provide good chemical resistance and high heat resistance.  Rubber elastomers, as they are also called, are classified into six groups: styrenic block copolymers, polyolefin blends, elastomeric alloys, thermoplastic polyurethanes, thermoplastic copolyesters and thermoplastic polyamides.    

When selecting products, industrial buyers can limit their search to either thermoset or TPE products.

Gel Elastomers

The GlobalSpec SpecSearch database also contains information about gel elastomers, highly viscoelastic polymer products that have excelled shock absorption and damping characteristics. Typically, they are produced via a two-part casting system. Subcategories include thermoplastic, polyurethane, and silicone gel elastomers.  Applications range from medical devices to motorcycle seats to computer keyboard wrist wrests.

Chemical System and Filler Material 

Industrial buyers need to specify the chemical system for elastomers and stock shapes, and can select products that use a filler material. There are six chemical systems, each of which provides characteristics suitable for specific applications.

• Fluoroelastomer products are used in applications that require superior chemical resistance or low friction.
• Polyethylene (PE) has good friction and mechanical properties. 
• Polyurethane (PU) provides excellent flexibility, impact resistance, and durability.
• Silicone rubber has excellent resistance to temperature extremes and can be compounded with additives to impart electrical insulation properties. It has a low degree of water resistance, however.
• Acrylics can be compounded with ethylene to provide a high degree of oil, ozone, ultraviolet (UV), and weather resistance.
• Butyl rubber is used to make products that are air tight and gas impermeable.

In terms of filler materials, some elastomer and rubber shapes contain chopped, continuous, wound, or aramid fibers. Others contain glass or metal fillers, inorganic or reinforced compounds, or carbon or graphite powders. Unfilled products are also available.

Forms and Sizes

Elastomer and rubber shapes are available as bars, films, plates, profiles, rods and shims with square, spherical, angular, rectangular, hexagonal, tubular, I-shaped, and T-shaped c ross-sections. Size and dimensional criteria include overall thickness, overall width or outer diameter (OD), overall length, and inner diameter (ID).

References

Elastomer Rubber Compounds – Types and References

Thermoset Elastomers - Rubber