TPU buyer's guide: chemistry, durometer, and grade selection

Thermoplastic polyurethane comes in hundreds of grades, and most selection mistakes trace back to picking in the wrong order. Hardness gets chosen first because it is the number everyone knows, and the chemistry gets assumed. Then the part meets hot water, or a cold dock, or a fuel line, and fails a durability test the datasheet never promised to pass.

This guide covers the selection sequence we walk through with TPU buyers, and what to check when qualifying a supplier.

How to select a TPU grade

Select in this order: first the soft-segment chemistry, matched to the environment the part lives in. Second the Shore durometer, matched to the part's mechanical job. Third the processing profile, matched to your equipment. Fourth the documentation, matched to your compliance requirements. Chemistry comes first because it is the decision you cannot compensate for later. A durometer that is slightly off changes how a part feels; the wrong chemistry changes whether the part survives.

Step 1: match the chemistry to the environment

TPU is built on a soft segment, and that soft segment sets the environmental resistance of everything you mold or extrude from it.

• Polyester TPU is the workhorse for dry mechanical service: the best abrasion resistance, mechanical strength, and resistance to oils, fuels, and heat. Its weak point is long exposure to hot water, steam, or humid heat.
• Polyether TPU is the choice for wet, cold, buried, or long-immersion service: the best hydrolysis resistance, low-temperature flexibility, and microbial resistance.
• Caprolactone TPU is a polyester type that keeps most of the mechanical performance while improving hydrolysis resistance. It earns its premium in demanding seals and parts that see both wear and moisture.

The deciding question is simple: what does the part touch, and at what temperature? Oil at room temperature points one way, water at 60°C points the other. For the full trade-off, see polyester vs polyether TPU: choosing by environment.

Step 2: set the durometer from the job

Hardness sets stiffness, sealing force, and wear behavior. TPU spans roughly Shore A 70 to Shore D 75, and the range breaks down by function. Soft grades, around Shore A 70 to 90, flex and conform: dynamic seals, flexible tube, grips, and overmolds. Medium grades, Shore A 90 to 98, carry most extrusion work: hose, film, cable jacket, belting. Hard grades, Shore D 50 to 75, hold shape under load: rollers, casters, scraper blades, and structural parts.

If you are replacing an existing part, measure it. A bench durometer reading on the real part beats guessing from feel, and it catches the cases where the incumbent material is a different polymer entirely. How the number is measured, and where the A and D scales cross over, is covered in TPU durometers and what they mean for your part.

Step 3: confirm the processing profile

Two grades with the same chemistry and hardness can still run differently. Before committing, confirm the grade matches your process:

• Process type. Injection molding grades and extrusion grades are formulated for different melt strength. An extrusion grade needs enough melt integrity to hold a profile shape out of the die; a molding grade needs to fill a tool fast and release clean.
• Melt behavior. Check melt flow data against the grade you run today. A large gap means new temperature profiles and possibly new tooling trim.
• Drying. TPU is hygroscopic and must be dried before processing. Confirm your drying equipment reaches the grade's specified conditions; the TDS states them per grade. Our TPU processing and regrind guide covers what happens when it doesn't.

Step 4: documentation and compliance

Pull the paperwork before the qualification run, since a missing statement can disqualify a grade late. A TDS and SDS should be available for every grade. Beyond that, ask for what your application requires: food-contact statements (FDA 21 CFR 177.2600) for select grades, RoHS and REACH statements, and UL or flame-performance data where the spec calls for it.

What to check when qualifying a TPU supplier

The grade is half the decision. The supply arrangement is the other half, and these are the questions that separate suppliers:

• Where is the material stocked? Regional stock means a schedule change does not strand your line behind ocean freight.
• How fast do samples move? Qualification stalls when samples take weeks. Same-day or next-day sample dispatch keeps a program on schedule.
• Is documentation per grade, on request, without a chase? TDS and SDS immediately; compliance statements within days.
• Can they cross-reference? A supplier who can read a competitor's datasheet and propose a match by hardness, chemistry, and processing profile saves you the translation work.
• Who answers technical questions? One accountable contact for grade selection, documentation, and shipping beats a relay chain of three parties.
• Does the volume model fit? Small qualification quantities now, container volumes later, without changing suppliers in between.

Matching a grade you already buy

Second-sourcing works from the specification, and three values determine fit: the Shore hardness, the soft-segment chemistry, and the melt behavior on your equipment. Send the datasheet of the grade you run, or the spec you need to hit, and a competent supplier will propose a match and a sample against it. Cross-references to commonly specified TPU grades are available on request; the confirmation always happens on your own tooling. The full second-sourcing walk-through is in sourcing Laripur TPU in North America.

Frequently asked

How do I choose between polyester and polyether TPU?

Match the chemistry to the environment. Polyester TPU leads on abrasion, mechanical strength, and oil and fuel resistance, so it suits dry mechanical service. Polyether TPU leads on hydrolysis resistance, low-temperature flexibility, and microbial resistance, so it suits wet, cold, or long-immersion service. Caprolactone TPU keeps most of the polyester mechanicals while improving hydrolysis resistance.

What Shore hardness do I need for my TPU part?

Softer grades around Shore A 70 to 90 flex and seal, so they suit dynamic seals, flexible tube, and grips. Harder grades from Shore A 95 through Shore D 75 hold shape under load, so they suit rollers, wear parts, and structural components. Start from the part's function, then confirm against the measured durometer of the existing part if one exists.

What information does a supplier need to recommend a TPU grade?

Four things: the application and environment (fluids, temperatures, outdoor or buried service), the target hardness or current grade, the process, and any compliance requirements. With those, a supplier can propose a grade and a sample in one pass.

Can I switch TPU brands without requalifying my tooling?

Usually the tooling carries over when the replacement matches hardness, chemistry, and melt behavior, but plan a qualification run. Processing windows differ between brands even at matching datasheet values, so validate on your own equipment before committing production.

Start with a sample

Tell us the application, the environment, and the hardness target, or send the datasheet of the grade you run today. We will propose a Laripur grade and send a sample with the TDS.