Browse the flexible filament section of any shop and you will find spools labelled TPU, spools labelled TPE, and the occasional one labelled both, with the two names used almost interchangeably. They are not the same thing, but they are not opposites either, and the relationship between them is the source of most of the confusion. The short, accurate answer is that TPU is a member of the TPE family, and that a spool sold as “TPE” is usually something softer and more awkward to print than a typical TPU. This post, a companion to the TPU post, sorts out what the terms mean, why sources seem to contradict each other, and how to work out what you are actually buying. It is built from published material data and technical sources rather than a hands-on test of every type.
What a thermoplastic elastomer actually is
TPE stands for thermoplastic elastomer, and it names a whole class of materials rather than one polymer. Thermoplastic elastomers are copolymers, or physical mixes of polymers (usually a plastic and a rubber), that combine rubber-like stretch with the ability to be melted and reshaped like a thermoplastic. The distinction that defines them is how the material holds itself together. Ordinary rubber is thermoset, meaning its chains are locked together by permanent chemical cross-links, so it can be stretched but never remelted. A thermoplastic elastomer replaces those permanent links with physical ones: hard regions in the material act like anchor points that hold the soft, stretchy regions in place at room temperature, then let go when heated. That is what lets a TPE be extruded through a nozzle and still snap back like rubber once it cools.
The TPU post covered exactly this mechanism for the urethane case, with its alternating hard and soft segments in one chain. The important point here is that this is a general idea, and there are several different chemical ways of achieving it.
The TPE family tree
| Class | Shorthand | What it is | Typical character |
|---|---|---|---|
| Styrenic block copolymers | TPS, TPE-S (SBS, SEBS and similar) | Rubbery blocks combined with rigid polystyrene blocks | Very soft, soft-touch feel, good UV resistance in SEBS types |
| Thermoplastic polyolefin elastomers | TPO, TPE-O | Blends based on polyolefins | Used widely outside 3D printing, for example roofing |
| Thermoplastic vulcanizates | TPV, TPE-V | Rubber particles dispersed in a plastic such as polypropylene | Better heat resistance |
| Thermoplastic polyurethanes | TPU | Block copolymer of hard urethane and soft polyol segments | Tough, abrasion-resistant, the most common flexible filament |
| Thermoplastic copolyesters | TPC, TPE-E | Polyester-based elastomer | Durable and heat tolerant |
| Thermoplastic polyamides | TPA, TPE-A | Nylon-based elastomer | Tough and chemically resistant |
That table is the key to understanding why TPU and TPE sources appear to disagree. By the strict definition, TPU is one of the TPE classes, which is how references such as Wikipedia and several manufacturer explainers describe it. By common filament-shop usage, “TPE” is often shorthand for the other TPEs, the softer, non-urethane ones, with TPU treated as the separate and more popular option. Both usages are in circulation, and neither is wrong. They are answering slightly different questions.
Why the label on the spool cannot be trusted on its own
This is the practical consequence, and it is worth stating plainly. A spool marked “TPE” might be a styrenic elastomer, a vulcanizate, or a urethane-based material that the maker simply prefers to call TPE. The academic literature illustrates the overlap: papers on printing “TPE” regularly discuss products such as NinjaTek’s NinjaFlex and Cheetah, which are generally described as urethane-based, alongside others, because to a materials scientist they are all thermoplastic elastomers. So a “TPE” label tells you the material is stretchy and meltable, and very little about how it will behave in your printer. The same is true in reverse, since some products sold as TPU are blended or modified.
The reliable approach is to read the manufacturer’s data sheet for the chemistry, the Shore hardness, the elongation and the recommended print temperature, rather than trusting either abbreviation. If the data sheet does not say what the base polymer is, that is itself worth noting.
How “TPE” (as usually sold) compares with TPU
| Property | Typical filament “TPE” | Typical TPU |
|---|---|---|
| Chemistry | Varies, often styrenic blends, vulcanizates or copolyesters | Urethane block copolymer |
| Hardness (Shore A, as reported) | Roughly 20A to 90A depending on the source | Roughly 60A to 98A, with many consumer spools at 85A to 95A |
| Feel | Softer, lighter, more rubbery | Firmer, tougher, more rigid for a given hardness number |
| Abrasion and chemical resistance | Generally lower | Generally better |
| Printability in FDM | Technically challenging, especially at the soft end | Easier, though still harder than PLA |
| Moisture sensitivity | Reported as somewhat lower than TPU, but still worth drying | Hygroscopic, with moisture causing bubbling and stringing |
| Strengths | Soft touch, high stretch, comfort grips | Durability, dimensional stability, wear resistance |
One honest caution about that table: the hardness figures come from sources that do not agree. One guide gives TPE as 30A to 90A and TPU as 60A to 98A. Another gives TPE as 20A to 80A and TPU as 60A to 95A. A third quotes TPU as 85A to 95A, and another extends the TPU range into the Shore D scale, up to 55D. The overlap is the real story. A 90A spool might be a TPU or a TPE, so hardness alone cannot tell you which you have, which is another reason to read the data sheet. There is also a subtle point from one of the sources worth keeping: rigidity and hardness are not the same thing, and a TPU generally feels stiffer than a TPE of the same Shore number.
Why softer is harder to print
The reason the softest TPEs are tricky is mechanical, and it is the same reason the TPU post gives for flexible filament in general, taken further. A filament is pushed through the extruder like a rope pushed from behind, and a stiff filament transmits that push cleanly while a soft one compresses and buckles. The softer the material, the less force it can transmit, so it is more likely to squash in the gap between the drive gear and the hotend entrance, get chewed, or tangle. Patent literature on very soft elastomers lists the failure modes explicitly: improper filament diameter, filament buckling, annular backflow, poor interlayer adhesion and poor bed adhesion, all traced back to the low modulus and hardness of the material. TPUs at 80A to 95A are stiff enough to cope with a well-set-up direct drive extruder. A 30A to 45A elastomer is on a different level of difficulty, and some are described as unsuitable for ordinary FDM entirely, partly because very soft materials also creep over time and lose dimensional stability.
Printing it: what carries over from TPU
Everything in the TPU post’s settings guidance applies, with the dial turned further the softer the material gets. A direct drive extruder is strongly preferred, and both the A1 and A2L have one. Print slowly, since a soft filament cannot be pushed fast. Keep retraction small or off, because retracting a compressible filament tends to cause more problems than it solves, which the retraction settings post and the stringing post cover from the other side. Dry the spool before printing, following the drying post, since even the less hygroscopic TPEs benefit and a damp spool compounds every other difficulty.
For temperature there is no universal TPE number, because the chemistry varies so much. Start from the manufacturer’s range for that specific spool and, if you want to refine it, a temperature tower as described in the temperature tower post is the right tool, run at the slow speed you will actually print at. On the plate, a textured PEI surface is generally friendly to flexible materials, though very soft ones can grip strongly, so the cautions in the bed adhesion post apply, and a skirt or small brim from the skirt, brim and raft post can help small, floppy footprints.
One practical constraint worth repeating from the TPU post: flexible filaments generally do not feed reliably through an AMS or AMS Lite, with Bambu’s own high-flow 95A TPU the notable exception. A soft TPE is even less likely to survive a long, curved filament path, so assume it needs an external spool feeding the toolhead directly.
What each is best for
| Use | Better fit | Why |
|---|---|---|
| Phone cases and protective covers | TPU, around 85A to 90A | Toughness and impact absorption matter more than softness |
| Wheels, rollers and wear parts | TPU, especially polyester-based grades | Abrasion resistance is a TPU strength |
| Living hinges and semi-flexible parts | TPU at the harder end, around 95A | Needs some rigidity as well as flex |
| Comfort grips and soft-touch handles | Softer TPE | The soft, rubbery feel is the point |
| Gaskets and seals | Softer TPE or soft TPU | Conformability matters, though soft grades are harder to print reliably |
| Toys and tactile pieces | Softer TPE | Soft feel, with the styrenic types noted for good surface feel |
| Outdoor use | SEBS-based TPE or a TPU chosen for UV and hydrolysis resistance | Check the data sheet, because chemistry decides UV and moisture behaviour |
How to choose without getting caught out
- Decide what the part needs: soft feel, toughness, abrasion resistance, or heat tolerance.
- Look past the TPE or TPU label to the data sheet, and find the base polymer and the Shore hardness.
- If you are new to flexible filament, start with a TPU around 90A to 95A, which is the forgiving end of the range, and move softer only when the part genuinely demands it.
- Check your hardware, since an external spool and a direct drive extruder matter more the softer the material gets.
- Dry it, print slowly with minimal retraction, and print a small test piece before committing to a long job.
The filament brands post is a useful companion here, because consistent diameter and a clearly documented chemistry matter even more with flexible materials than with PLA.
The summary
TPE is the family and TPU is one of its members, which is why the two names keep getting used for each other. In everyday filament shopping, “TPE” tends to mean a softer, lighter, more rubbery material that is harder to print and less resistant to abrasion, while TPU means the firmer, tougher, more forgiving urethane-based option. The hardness ranges overlap, and some products carry whichever label the maker prefers, so the spool’s name is a weaker guide than its data sheet. For most people, TPU is the sensible place to start, and a true soft TPE is worth reaching for only when a part really needs that extra softness and you have the hardware and patience to print it.
