What makes an "Engineering" Thermoplastic Elastomer "Higher Performance"?

In the world of Thermoplastic Elastomers(TPE's), it is generally agreed that there is seven basic categories in this material classification of plastics; Elastomeric PVC Blends/Alloys, Thermoplastic Olefins(TPO's), Styrenic Block Copolymers(SBC's), Dynamically Vulcanized Alloys(DVA's), Thermoplastic Polyurethane(TPU), Copolyester Elastomers(COPE), and Polyether Block Amides(PEBA's). Even with all the "niche" additions in the last 10 to 15 years these categories have, in general, remained constant. Graphically, from a cost/performance point of view, these categories can be laid out as shown below:

The reader will notice that the last three categories in the upper right corner are referred to as "Engineering" Thermoplastic Elastomers(ETPE's). Besides the higher cost of these materials, why do these materials claim this name that indicates higher performance? What does this mean?

The fact is, these ETPE's will not command a higher cost if their performance will not "add value" to an application beyond what the other four categories can add. The fact also is that, like their rigid plastic relatives, there is overlap in the property and feature matrix that these different TPE categories offer to the designer that may make several of them "adequate" material choices for specific applications. In fact, some applications may demand properties that may make the non-ETPE a better material choice.

In applications that require clarity, low temperature flexibility, higher heat resistance, resistance to certain chemical environments, bondability to specific substrates, decoration, lower durometers, compression set performance, rubberiness/grippiness, specific physical/mechanical property requirements, low weight, a design review of all of the above noted categories should be done.

In general, ETPE's will stack up very well in the above review. They will be superior in the physical/mechanical(especially abrasion, tensile) property category and will be more limited in the lower durometer properties as they extend down to the 65 Shore "A" range. But, the other non-ETPE's will be viable candidates for applications where the above noted properties are critical.

Where ETPE's really set themselves apart from the non-ETPE's is when the application requires dynamic flexure or excellent flex fatigue properties needed in constant movement of the part or composite. Applications such as high speed conveyance and power transmission belting, high performance athletic footwear parts, silent gears, textile composites, robotic wire and cable jacketing, automotive CVJ boots, high performance scuba fins, bumpers, and many more indicate the ETPE performance edge for these type of dynamic applications.

These materials have excellent inherent "hysteresis" properties, which means there is less heat loss when flexed than the non-ETPE's. This means less energy loss due to deformation and less permanent degradation of the polymer when stressed. They also have no plasticizers or oils that will leach out over time, which means they are much less likely to crack under stress. Similarly, ETPE's can withstand repeated shock which, as long as it is non-catastrophic, means they can be used as protective covers for golf balls, automotive body side moldings, bumpers, and the like.

ETPE's are also processed via injection molding, profile extrusion, film/sheet extrusion, vacuum forming, rotational molding, powder coating, etc., and can be fabricated by a number of different joining techniques including RF welding, spin welding, heat welding, adhesive lamination, flame lamination, and ultrasonic welding. They are also decorated by most of the common printing and decorating techniques.

The bottom line is that if your application requires excellent flex life, one of the ETPE material categories above is a good starting point, and probably a good ending point, for your application. This is along with the rest of their excellent property/feature matrix. It would be well worth your while to take a look at these versatile TPE materials when your next application requires an elastomer.