When I first started reviewing polymer materials for hydraulic hose making, I assumed PET and TPU were basically interchangeable. They're both thermoplastics. Both show up in industrial hose specs. Both get marketed as 'durable.' Then we quoted a 5/16 hydraulic hose job and the customer asked a simple question: Which one should actually touch the fluid?
That question changed how I read datasheets. I'm a quality/compliance manager at a polymer processing company, and I review roughly 300 incoming material lots and finished hose samples every month. I've rejected about 11% of first deliveries in 2024 for spec deviations. So when I talk about PET vs TPU, I'm coming at it from the inspection side, not the sales side.
If you've ever read an old engineering report from Goodyear Tire and Rubber Company, you'll know what I mean. They tested the assembled product, not just the raw compound. That's the mindset that matters for hydraulic hose making.
PET vs TPU: The Framework I Use
Most material comparisons treat PET and TPU as competitors for the same layer. In a 5/16 hydraulic hose, they're more often teammates: PET braid carries the pressure load, and TPU handles the flexible, oil-resistant layers. But you still need to decide which one goes where. If you choose wrong, you won't see the failure on day one. You'll see it on day 90.
I compare five things: tensile behavior, flex fatigue, temperature and chemical resistance, lot-to-lot consistency, and total installed cost.
1. Tensile Behavior: The Surprising Part
PET is a polyester. It's drawn into high-tenacity yarn with low elongation. In a hose, that means stability under pressure. TPU is a polyurethane elastomer. It's tough, but it stretches. Stretch might sound good—until a 5/16 hydraulic hose swells and loses pressure.
Here's the surprise: in a simple tensile test, TPU can show a higher ultimate tensile strength than standard PET yarn, depending on grade. On a spec sheet, TPU often wins. But in a pressure cycle, PET resists creep much better than TPU. Creep translates into hose diameter growth, and diameter growth kills pressure retention.
On our spec sheets, PET reinforcement is usually called out as high-tenacity polyester yarn. Tenacity means breaking strength per denier. We require a certificate of analysis for every spool. That data matters more than the marketing brochure.
According to ASTM D638, tensile testing is a single pull to break. It tells you one thing. It doesn't tell you how a material behaves over 100,000 pressure cycles. For reinforcement, PET beats TPU. Period.
2. Flexibility and Flex Fatigue
TPU is naturally more flexible. That's why you see TPU as the inner tube or outer cover on thermoplastic hydraulic hoses. It survives repeated bending, torsion, and abrasion. PET braid is stiffer, but if the PET is in the reinforcement layer, it doesn't need to flex as much. The TPU around it absorbs the motion.
In our lab, a 5/16 hydraulic hose with a TPU liner and PET braid can handle a tighter bend radius than an all-PET construction would. Actually, I've never come across an all-PET hydraulic hose—PET is too stiff for a dynamic hose. The point is, flex rating depends on the system.
Here's an observation from the shop floor: TPU covers get scratched and nicked, but they don't crack the way hard plastics do. PET braid, if exposed, can fatigue and fret. The combination protects both.
If you ask me to choose one material for a lightweight thermoplastic hose that will be dragged across a shop floor, I choose TPU. It survives abuse. For a reinforced 5/16 hydraulic hose, I'd rather have PET braid in the middle and TPU on the outside. Not ideal? Pretty close.
3. Temperature, Chemical Resistance, and Fluid Contact
Hydraulic fluid is unforgiving. TPU has good oil and fuel resistance, which makes it a natural choice for fluid contact. PET is more resistant to some solvents, but it can hydrolyze in hot, humid service. Neither is perfect. For a 5/16 hydraulic hose, I'd rather see TPU on the fluid side and PET reinforcement outside the fluid path.
That said, TPU grades aren't all the same. Polyester-based TPU can also hydrolyze; polyether-based TPU handles moisture better. Check the grade. I don't have hard data on every TPU grade out there—there are hundreds—but based on the material certifications I've reviewed, hydrolysis is the failure mode I'd worry about most in hot service.
One supplier wanted to substitute a polyester-based TPU for a polyether TPU to save lead time. In a room-temperature air application, it might have worked. In a hydraulic hose making environment, I couldn't justify it. The chemical compatibility was not the same.
4. Processing Consistency: What Actually Hurts
TPU is hygroscopic. If it picks up moisture, extrusion looks fine at first, then bubbles show up in the wall. In Q1 2024, we rejected 3 out of 12 TPU lots before we implemented a mandatory pre-extrusion moisture test. They warned me about this years ago. I didn't listen. A $9,000 redo later, I listen.
PET yarn is more forgiving in our braiding process, as long as the supplier keeps the denier and finish consistent. The consistency issue is real. If you're making a 5/16 hydraulic hose to a tight spec, a small viscosity drift in the TPU liner can change the final tube ID. That's a red flag.
Now every TPU lot sits in a moisture-controlled cabinet for at least 12 hours before it hits the extruder. Yes, that slows things down. It also cuts our defect rate.
If you're working from an OEM spec that references Goodyear Tire and Rubber Company's original part, the approved material list is often behind a Goodyear login. That login can be annoying, but it's also a source of truth. Use it. Data beats opinions.
5. Cost and Delivery Certainty
Let's talk money. As of January 2025, TPU pellets were roughly 2.5 to 3 times the price of PET on a per-pound basis in the supplier quotes I collected for our Q1 cost review. Verify current pricing before you budget; prices move. But don't make the mistake of asking 'which is cheaper?' Ask 'which is cheaper for this function?'
People think expensive materials deliver better quality. Actually, the causation runs the other way: vendors who control consistency can charge more. The material price is only part of the total cost.
Last year we compared two material programs for the same 5/16 hydraulic hose. The 'cheap' PET yarn had inconsistent denier and caused braid tension spikes. We lost 2 shifts. The more expensive yarn ran clean. It was worth the difference.
This is where I get firm about time certainty. When a customer needs 500 ft of 5/16 hydraulic hose in ten business days, I'm not going to experiment with a new TPU grade or an untested PET braid. In March 2024, we paid $400 extra for expedited yarn delivery. The alternative was missing a $15,000 order. That was a no-brainer. Rush fees don't just buy speed—they buy certainty.
Selection Advice: What to Actually Specify
So here's my bottom line for a 5/16 hydraulic hose:
- Choose PET reinforcement when you need pressure hold, dimensional stability, and low creep.
- Choose TPU liner or cover when you need flexibility, oil resistance, and abrasion resistance.
- Choose an all-TPU hose for lightweight and flexibility at moderate pressure, but budget for higher material cost and stricter processing control.
If a supplier tells you PET or TPU is 'better' with no qualifier, ask them for the application. Honestly, the best answer for most hydraulic hose making is a combination—TPU tube plus PET reinforcement. That's not a cop-out. It's accepting that they solve different problems.
I don't have hard data on every possible hydraulic fluid or hose construction, but I've seen enough failures to know that material selection is not a popularity contest. Stop trying to crown a global winner. Match the material to the layer, and match the layer to the service. That's it.
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