TPC-ET vs TPU: when a copolyester elastomer wins

TPU covers an enormous amount of ground, and for most flexible parts it is the right call. But every TPU buyer eventually meets a part that sits at the edge of what the material does well: a gasket that relaxes under years of bolt load, a connector that lives next to an engine, a jacket that has to stay flexible at -40°C and below. That is where a thermoplastic copolyester elastomer, TPC-ET, earns its place.

What is TPC-ET?

TPC-ET (also written COPE or TPC, and known to many buyers by the incumbent trade names Hytrel and Arnitel) is a block copolymer built on hard crystalline polyester segments and soft polyether segments. The hard segments give strength, dimensional stability, and high-temperature performance. The soft segments give flexibility, elastic recovery, and toughness at low temperatures. Like TPU, it processes on standard thermoplastic equipment: injection molding, extrusion, blow molding, no vulcanization step.

The two materials are close cousins in the thermoplastic elastomer family, which is why the comparison comes up in real sourcing decisions rather than textbooks. The differences show up at the edges of the service envelope.

Where TPC-ET wins

• Continuous heat. The crystalline hard segment holds its structure at temperatures where TPU softens. Parts that live hot, under-hood components, high-temperature air ducting, hot-fluid contact, run longer in TPC-ET.
• Compression set under sustained load. A seal's job is to push back, for years. TPC-ET holds compression set better than TPU and SEBS under sustained compression, which is why it is specified for static seals, face seals, gaskets, and backup rings.
• Creep resistance. Under continuous stress, TPC-ET's crystalline network resists slow deformation better, so clipped, bolted, and press-fit parts keep their dimensions.
• Deep cold. Elastomeric TPC-ET grades stay flexible to around -60°C, below where most TPU grades stiffen.
• Fatigue and spring behavior. High resilience and fatigue resistance suit flexing parts: bellows, boots, energy-return components, living hinges.
• Adhesion in 2K overmolding. The polar ester chemistry bonds naturally to ABS, PC, SAN, PBT, and POM, where non-polar TPEs struggle.

Where TPU keeps the advantage

• Abrasion. Polyester TPU remains the reference for sliding wear: hose covers, scraper blades, load wheels, footwear outsoles.
• Soft hardnesses. TPU reaches down into the Shore A range, roughly Shore A 70 and up. TPC-ET starts around Shore D 28, which corresponds to the firm end of TPU territory. A soft, rubbery hand means TPU.
• Cost. TPU generally carries a lower price per kilogram. If TPU meets the service conditions, it is usually the economical answer.
• Optics and feel. Transparent grades and soft-touch surfaces are TPU strengths, which is part of why footwear and consumer overmolds stay there.

The hardness overlap, read correctly

TPU spans roughly Shore A 70 to Shore D 75. TPC-ET spans roughly Shore D 28 to 72, in two behavior families: elastomeric grades (Shore D 28 to 45) that act like a soft rubber with excellent fatigue and cold performance, and plastomeric grades (Shore D 46 to 72) that act like an engineering plastic with elastomer toughness. In the overlap zone, hardness stops being the deciding variable. The environment decides: sustained heat, sustained compression, or long-term stress favor the copolyester; wear and softness favor the urethane.

How to decide on a real part

Ask three questions in order. What is the hottest temperature the part sees continuously, and for how long? Does the part sit under sustained compression or stress it must recover from? Does it need a soft Shore A feel or heavy sliding wear resistance? Heat, compression, and creep point to TPC-ET. Softness and abrasion point to TPU. Both materials are legitimate answers for seals, jackets, hose, and molded flexible parts in between; the datasheet values on the specific grades settle it.

We supply both families, Laripur TPU and Sipolprene TPC-ET, so the recommendation follows the part rather than the product line. If you are working from an existing copolyester spec, see matching a TPC-ET spec: a Sipolprene cross-reference guide.

Frequently asked

What is TPC-ET?

A thermoplastic copolyester elastomer: a block copolymer of hard crystalline polyester segments and soft polyether segments. The hard segments give strength, dimensional stability, and heat performance; the soft segments give flexibility, elastic recovery, and low-temperature toughness. It processes on standard thermoplastic equipment.

When should I use TPC-ET instead of TPU?

When the part runs hotter than TPU handles comfortably, when a seal or gasket must hold compression set under sustained load, when long-term stress causes creep, or when service reaches very low temperatures. TPU keeps the advantage on abrasion, soft Shore A hardnesses, and cost.

Is TPC-ET harder than TPU?

The ranges overlap but sit differently. TPU spans roughly Shore A 70 to Shore D 75 and reaches much softer grades. TPC-ET spans roughly Shore D 28 to 72, so its softest grades match the firm end of TPU. In the overlap, the environment decides, and hardness stops being the differentiator.

Can TPC-ET be blended into PVC?

Yes, with a grade engineered for it. A PVC-modifier grade with a controlled melting point around 150°C compounds into PVC below its degradation threshold, improving elongation, oil resistance, cold flex, and abrasion resistance.

Working through a TPU-or-TPC-ET decision?

Tell us the service temperature, the load, and the environment. We will recommend a Laripur or Sipolprene grade and send a sample for qualification.