Material selection
TPE vs TPU
Both are the default overmolding elastomers for a soft-touch surface, and both injection mold directly onto a rigid substrate without a separate bonding step. The difference that actually decides between them is what the surface has to survive after it ships: a part that only gets touched, or a part that gets worn against. The numbers below are the same published datasheet values used on each material's own page, set side by side.
| TPE (SEBS) | TPU | |
|---|---|---|
| Density | 0.90–1.05 g/cm³ | 1.10–1.25 g/cm³ |
| Hardness | 20–90 Shore A | 70 Shore A – 75 Shore D |
| Tensile strength | 5–12 MPa | 25–55 MPa |
| Elongation at break | 500–800 % | 400–600 % |
| Mold shrinkage | 1.0–2.0 % | 0.8–1.6 % |
| Service temperature | −40 to 70 °C | −30 to 80 °C |
| Relative cost | Low | Medium |
Published values for unfilled grades at 23 °C unless stated, taken from each material's own datasheet page. Confirm against the supplier datasheet for the grade you specify.
What TPE (SEBS) is
SEBS-based TPE is the material behind almost every soft-touch grip on a consumer product. It is available down to 20 Shore A, far softer than TPU gets, and specific grades bond chemically to ABS or PP during overmolding without a primer. The trade-off is durability: it is weaker and less abrasion resistant than TPU, so it belongs on surfaces that are touched rather than surfaces that are worn, and soft grades take a set under sustained compression rather than holding a structural seal.
What TPU is
TPU is a block copolymer with hard and soft segments: the hard segments behave like a thermoplastic and let the material be remelted and molded, the soft segments give rubber-like elasticity. It has the best abrasion resistance of any common polymer and survives oils and greases that attack natural rubber and most TPE grades, but it starts at 70 Shore A, so it cannot reach the very soft, cushioned feel TPE's low end covers, and it is hygroscopic enough that it molds badly wet, needing 2 to 3 hours of drying at 80–100 °C before every run.
TPE against TPU
| TPE (SEBS) | TPU | |
|---|---|---|
| Hardness range | 20–90 Shore A, reaches far softer | 70 Shore A – 75 Shore D, starts where TPE's upper range ends |
| Abrasion and wear resistance | Weaker, not for surfaces that see repeated contact | Best of any common polymer, the default for wheels, rollers and cable jackets |
| Oil and grease resistance | Moderate, depends on the grade | Good, survives fluids that attack natural rubber |
| Overmolding bond | Chemical bond to ABS or PP with a matched grade, plus a mechanical interlock | Chemical bond to ABS, PC or PC/ABS with a matched grade and a hot substrate |
| Processing | Forgiving, drying usually unnecessary, melt 180–220 °C | Demanding, must dry 2–3 hours at 80–100 °C or it hydrolyses in the barrel, melt 190–230 °C |
| Relative cost | Low | Medium |
Which one, for which part
- Soft-touch grips, buttons, and closures that only get touched, not worn is TPE's case: it reaches softer, bonds to PP as well as ABS, and costs less.
- Wheels, castors, rollers, cable jacketing, or any surface under repeated abrasion is TPU's case: it has the best abrasion resistance of any common polymer.
- Seals and gaskets exposed to oils or greases favour TPU, which survives fluids that attack natural rubber and most TPE grades.
- A part that needs a firm, structural flex rather than a cushioned feel fits TPU's 70 Shore A floor better than pushing a TPE grade to the top of its range.
- Overmolding onto polypropylene specifically favours TPE; TPU's overmolding grades are matched to ABS, PC, and PC/ABS, not PP.
Our status
Trumould molds both TPE and TPU in-house on the same press range used for the rigid substrate, and TPU also runs through our 3D printing capability for flexible prototypes. Send the part, the surface it has to survive, and target volume, and the quote states which elastomer is recommended and why, not just a price for whichever one you asked about first.
Specifying this part?
Send your CAD and target volumes. We come back with a price, a lead time, and any material or design notes that would reduce either.