Olefins: Thermoplastic olefin (TPO) elastomers are available in several grades, having room-temperature hardnesses ranging from 60 Shore A to 60 Shore D. These materials, being based on polyolefins, have the lowest specific gravities of all thermoplastic elastomers. They are uncured or have low levels of crosslinking. Material cost is mid-range among the elastoplastics.

These elastomers remain flexible down to -60°F and are not brittle at -90°F. They are autoclavable and can be used at service temperatures as high as 275°F in air. The TPOs have good resistance to some acids, most bases, many organic materials, butyl alcohol, ethyl acetate, formaldehyde, and nitrobenzene. They are attacked by chlorinated hydrocarbon solvents. Compounds rated V-0 by UL 94 methods are available.

The four oldest thermoplastic elastomer types are polyurethanes, polyester copolymers, styrene copolymers, and the olefinics. Mechanical properties of the first two types are generally higher than those of the last two. Dynamic properties, such as flex life are also generally better. Newest TPEs are three classes of high-performance materials. One is based on polyamide (nylon) chemistry; another, called elastomeric alloys, consists of polymer alloys of an olefinic resin and rubber. The third group, melt-processible rubbers, are sold by Du Pont under the Alcryn tradename.