When engineers compare TPU grades, the first instinct is to line up the hardness numbers. That is the wrong place to start. The decision that most often determines whether a part survives its service life is the soft-segment chemistry: polyester, polyether, or caprolactone. Get that right and the part lasts. Get it wrong and a perfectly specified hardness will not save it.
Here is what the three families actually do, and how to pick between them.
The two families, and one in between
All thermoplastic polyurethane is built from alternating hard and soft segments. The hard segment gives strength and sets the hardness. The soft segment sets the environmental resistance, and it comes in two main chemistries with a third that splits the difference:
- Polyester-based TPU: the abrasion, strength, and oil-resistance leader.
- Polyether-based TPU: the hydrolysis, cold, and microbial-resistance leader.
- Caprolactone-based TPU: a polyester type that keeps most of the strength while improving hydrolysis resistance.
Polyester TPU: abrasion, oil, heat
Polyester grades are the workhorses. They give the highest abrasion resistance, the best mechanical strength, and strong resistance to oils, greases, fuels, and heat. If a part drags, scuffs, or runs in contact with hydrocarbons, polyester is usually the starting point. This is why polyester grades dominate extruded hose and tube, conveyor and drive components, and wear parts.
The trade-off is hydrolysis. The ester bonds react slowly with water, and heat and humidity speed the reaction up. A polyester part in dry or oily service can last for years. The same part in long-term hot, humid, or immersed service can soften and lose strength. That single failure mode is the reason the other two families exist.
Polyether TPU: hydrolysis, cold, microbial
Polyether grades resist hydrolysis far better, so they hold up in wet, humid, buried, or immersed service where polyester would degrade. They also stay flexible at lower temperatures and resist microbial and fungal attack, which matters for outdoor, marine, and medical-adjacent parts.
Polyether gives up some abrasion and oil resistance relative to polyester, but it is not a weak material. For seals exposed to water-based hydraulic fluids, cold-weather tubing, and parts that live outdoors, it is the safer long-term choice.
Caprolactone TPU: the middle path
Caprolactone grades are a polyester-type chemistry that keeps much of the mechanical strength and abrasion resistance while improving hydrolysis resistance. They are a common answer for parts that see both heavy wear and some moisture, such as demanding dynamic seals, where neither a standard polyester nor a polyether grade is an ideal fit on its own.
A quick decision guide
Start with the environment, then narrow by hardness:
| If the part sees... | Start with |
|---|---|
| Abrasion, drag, oils, fuels, heat (dry service) | Polyester |
| Water, humidity, immersion, water-glycol fluids | Polyether |
| Cold or sub-zero service | Polyether |
| Outdoor, marine, microbial exposure | Polyether |
| Both heavy wear and some moisture | Caprolactone |
Hardness is a separate decision
Two grades at the same Shore hardness can behave very differently if their chemistry differs. Choose the chemistry for the environment first, then choose the hardness for the mechanical job. We cover the hardness side in the versatility of TPU: durometers and their impact on innovation.
Frequently asked
Is polyester or polyether TPU stronger?
Polyester TPU generally has higher abrasion resistance and mechanical strength and better oil, fuel, and heat resistance. Polyether is not weaker in a general sense; it trades some of that abrasion and oil performance for much better hydrolysis resistance, low-temperature flexibility, and microbial resistance. The right choice depends on the environment, not on which wins on paper.
Why does polyester TPU fail in hot water?
The ester bonds in polyester TPU are susceptible to hydrolysis, a reaction with water that breaks the polymer chains. Heat and humidity speed it up, so a polyester grade in long-term hot or humid service can soften and lose strength. Polyether and, to a lesser degree, caprolactone grades resist hydrolysis far better.
What is caprolactone TPU?
Caprolactone TPU is a polyester-type thermoplastic polyurethane built on a polycaprolactone soft segment. It keeps much of the strength and abrasion resistance of polyester grades while improving hydrolysis resistance, which makes it a common middle-ground choice for demanding seals.
Sourcing Laripur TPU
P.A.T. Products is the North American distributor for COIM's Laripur TPU, and the line covers all three families across the full hardness range. Tell us the environment the part lives in and we will recommend a chemistry and grade, send a sample, and provide a cross-reference if you are moving off another brand.
View the TPU product page