FDM Part VIII Thermoplastic Elastomers

FDM Polymers — A Technical Reference ›

Part VIII — Thermoplastic elastomers

The thermoplastic-elastomer family — every flexible filament in commercial FDM. ISO 18064 defines TPE as the umbrella term for the whole category; §16.1 uses that taxonomy to sort out what vendors actually ship under the TPU, TPE, TPEE, and PEBA labels before the chapter turns to the process physics all of them share.

16. TPU, TPEE, PEBA, and foaming elastomers

Thermoplastic elastomers are the flexible-filament category in commercial FDM — polymers that combine rubber-like elasticity (200–700% elongation at break) with the meltability and recyclability of thermoplastics. TPU (thermoplastic polyurethane) dominates the consumer market on volume. TPE (thermoplastic elastomer) is — per ISO 18064 — the umbrella term for this entire category, TPU included, though spool labels routinely use it as if it named a separate soft material; §16.1 untangles that. TPEE (thermoplastic polyester elastomer, sometimes COPE) is a polyester-based elastomer with higher heat and chemical resistance than TPU. PEBA (polyether block amide, marketed under the Arkema Pebax trade name) is a polyamide-based elastomer with the lowest density and best dynamic-flex performance in the family. Foaming elastomers (chemical-blowing-agent flexible filaments) are a separate functional category that reduces printed-part density by 30–50% and is covered in §16.9.

16.1 “TPE” is the umbrella, not a material: ISO 18064 nomenclature

ISO 18064:2022 (Thermoplastic elastomers — Nomenclature and abbreviated terms) settles the vocabulary this market refuses to: TPE is the umbrella term for every thermoplastic elastomer, subdivided by hard-segment chemistry into six named classes plus a catch-all. Filament vendors invert this. On spool labels, “TPE” is used as if it named a specific material distinct from TPU — most often a styrenic-block compound (ISO class TPS, typically SEBS-based) or a thermoplastic polyolefin elastomer (ISO class TPO) that the vendor did not identify further. Under the standard, every TPU spool is a TPE by definition; a spool labeled only “TPE” tells you nothing beyond “flexible.” This is the same failure mode as the PAHT story of §2.3, with the same remedy: the technical datasheet, not the label, identifies the chemistry.

ISO 18064 class	Hard-segment chemistry	Market / trade names	Presence in FDM filament
TPA	Polyamide block (ether/ester soft segments)	PEBA; Arkema Pebax, Evonik Vestamid E	Niche premium — the PEBA sections of this chapter
TPC	Copolyester	TPEE, COPE; Envalior Arnitel, Celanese Hytrel (ex-DuPont)	Sparse (Arnitel ID 2045; 3DXTech's discontinued 3DXFLEX TPC)
TPO	Olefinic blend (PP + EPR/EPDM, not cross-linked)	“TPO” — frequently sold as just “TPE”	Rare as filament; behind some budget “TPE” SKUs
TPS	Styrenic block copolymer (SBS, SEBS, SEPS)	“Soft TPE” compounds	The usual chemistry behind budget “TPE” filament
TPU	Polyurethane	TPU 85A/95A/64D; NinjaFlex, FilaFlex, PolyFlex	Dominant — the consumer flexible default
TPV	Dynamically vulcanized rubber in a thermoplastic matrix (PP + EPDM)	Santoprene-class	Essentially absent from FDM
TPZ	Unclassified / other	—	Catch-all for chemistries outside the named classes

_{Table 16.1 — ISO 18064 TPE classes mapped to FDM market terms. The standard also defines subclass codes that occasionally surface on datasheets — e.g. TPA-ET (polyether-soft-segment polyamide TPE, the Pebax chemistry), TPC-ET (the Arnitel/Hytrel chemistry), TPU-ARET (aromatic hard segment, polyether soft segment). The 2022 edition restructured the styrenic subclasses into TPS-H (hydrogenated soft segment) and TPS-N (non-hydrogenated) — verified against the standard's own text (ISO 18064:2022, §6.4; verified July 2026 — see D.6); the older 2003/2014 codes such as TPS-SEBS persist on datasheets either way. Filament TDSs rarely go past the class level. Note the naming collision: “TPC” is both the ISO class code and a former product name (3DXFLEX TPC), where the two happen to agree. Where this volume's consolidated tables (Table 3.1, Table 24.1, Appendix A.3) say “TPU/TPE”, read: TPU plus the generic soft blends — typically TPS or TPO — sold under the bare “TPE” label.}

16.2 Chemistry: hard segments and soft segments

The engineering elastomer families of this chapter — TPU, TPEE, PEBA — are segmented block copolymers of alternating hard and soft segments; the TPS and TPO compounds behind generic “TPE” spools are styrenic triblocks or physical blends instead (§16.1). The hard segments provide mechanical strength, dimensional stability, and the upper service temperature; the soft segments provide elasticity. The chemistry of the hard segment is what distinguishes the four polymer families covered here.

TPU (ISO class TPU) uses aromatic diisocyanate (typically MDI) chain-extended with short diols to form urethane hard segments, and polyester or polyether polyols as soft segments. Polyester-based TPU has better mechanical envelope, abrasion resistance, and oil resistance; polyether-based TPU has better hydrolytic stability and low-temperature flexibility. Filament TDSs rarely disclose which soft-segment chemistry is in the product.

TPEE (also called COPE — copolyester elastomer; ISO class TPC) uses semi-crystalline polyester hard segments and amorphous polyether soft segments. The crystalline hard segments produce higher heat resistance (continuous service to ~120 °C vs TPU's ~80 °C) and better creep resistance under sustained load, at the cost of narrower processing windows and more aggressive crystallization shrinkage. TPEE is the elastomer for parts that load mechanically while flexing at elevated temperature; TPU is the elastomer for everything else in that envelope.

PEBA (ISO class TPA) combines polyamide hard segments (typically PA12, sometimes PA11 in the bio-sourced Pebax Rnew grades) with polyether soft segments (typically PTMG or PEG). The polyamide hard segments give PEBA exceptional dynamic-flex performance — among the lowest hysteresis loss per cycle of any commercial elastomer, which is why supercritical-foamed PEBA (Nike's ZoomX, introduced 2017) has dominated top-tier carbon-plate racing midsoles. It is not the universal midsole material, however: expanded TPU (Adidas Boost) remains in wide use, and recent premium foams also draw on supercritical EVA and aliphatic TPU. PEBA's bulk density runs around 1.01–1.04 g/cm³ (near water density — the lowest of the elastomer chemistries in commercial FDM filament form), giving it the highest stiffness-to-weight and toughness-to-weight envelopes in the elastomer family. The polyamide hard segments also extend the useful temperature range: PEBA stays flexible down to -40 °C and sustains 70–90 °C continuous service, with the stiffest grades reaching ~100 °C short-term. The trade is cost — PEBA filament typically prices at 3–5× equivalent TPU.

16.3 Shore hardness: the headline specification

Shore hardness on the A and D scales is the single most important specification on a flexible filament. The A scale measures soft elastomers (0–100); the D scale measures hard elastomers and rigid plastics (0–100). The scales overlap: Shore 90A is approximately equivalent to Shore 40D. Conventionally, TPU is quoted on the A scale until ~95A, then switches to the D scale at the rigid end; TPEE is quoted across the A and D scales depending on grade; PEBA is quoted almost exclusively on the D scale (Pebax grades run from 25D for the softest commercial product through 72D for the rigid end). Most filament hardness values cluster in well-known bands:

Shore	Typical feel	Print difficulty	Common applications
60A	Soft rubber band; deforms easily under finger pressure	Very difficult; direct drive mandatory; very slow print speeds	Cosmetic grips, soft seals, anatomical models
70A	Soft tire tread; flexes substantially in hand	Difficult; direct drive strongly preferred	Vibration dampers, soft-touch overmolds, soft phone cases
80A–85A / 25D–35D	Medium rubber; comparable to a soft eraser	Moderate; direct drive preferred; Bowden marginal (§16.5)	Flexible hinges, gaskets, watch bands, casters; soft PEBA running-shoe applications
90A–95A / 40D–45D	Firm rubber; harder than a typical eraser	Easier; Bowden workable at the 95A end (§16.5)	Drone tires, mechanical bumpers, durable phone cases — the consumer default
60D–72D	Hard plastic with slight flex; comparable to flexible PP	Easy; prints like a slightly rubbery rigid material	Living hinges, snap-fits with high cycle count, industrial bushings, rigid PEBA medical tubing

_{Table 16.2 — Shore hardness landscape for FDM elastomer filaments. The print-difficulty axis tracks hardness inversely: each 10-point drop on the A scale roughly doubles the printability challenge. Most consumer first-time flexible-filament users should start at 95A — softer materials demand hardware and skill that this hardness range does not require.}

16.4 Property envelope

Elastomer mechanical properties are dominated by Shore hardness and base polymer chemistry. The values below are representative ranges; individual filaments vary within each band.

Property	TPU 95A	TPU 64D	TPEE (~55D)	PEBA 40D / 55D
Density (g/cm3)	1.20–1.25	1.15–1.20	1.10–1.20	1.01–1.04
Tensile strength (MPa)	30–45	40–55	25–40	35–55
Elongation @ break (%)	400–600	200–400	300–500	400–700
Tear strength (kN/m)	80–120	100–150	80–130	100–180
Continuous service (°C)	70–80	70–85	100–120	70–90
Useful low-temp flex (°C)	-20	-20	-30	-40
Compression set (%)	25–40	20–35	15–30	15–25
Hydrolytic stability	fair (polyester) / good (polyether)	fair (polyester) / good (polyether)	good	excellent

_{Table 16.3 — Elastomer property envelope by family. The PEBA column is the high-performance reference point: low density, broad temperature range, exceptional dynamic flex, excellent hydrolytic stability. For applications where weight, dynamic-flex performance, or wet-service durability matter, PEBA outperforms TPU enough to justify the cost premium; for everything else, TPU is the practical default.}

16.5 Print process: the filament-buckling problem

Flexible filaments push the limits of FDM hardware in a way that rigid materials do not. The extruder gear advances filament into the hotend; the filament must resist the back-pressure created by melt flow through the nozzle. Rigid filament does this easily — the filament column is stiffer than the back-pressure. Flexible filament does not: above some critical back-pressure (which depends on the Shore hardness, the filament path geometry, the nozzle restriction, and the print speed), the filament buckles inside the filament path between the extruder gear and the hotend entry, producing under-extrusion or a jammed extruder.

The engineering response is to constrain the filament path. Direct-drive extruders mounted on the toolhead — where the filament traverses ~30–50 mm from gear to nozzle melt zone — print reliably down to ~85A. Bowden-tube extruders with ~500–800 mm of PTFE tubing between gear and hotend struggle with anything softer than 95A. Constrained-path extruders — direct-drive designs that physically constrain the filament between rollers or in a rigid channel all the way to the nozzle entry — extend that down to ~60–70A. Single-material multi-extruder hardware that shares one nozzle across several filament feeds typically uses Bowden-style routing between buffer and toolhead, which restricts those systems to 95A and harder TPU unless the vendor specifies otherwise.

PEBA prints more forgivingly than TPU at equivalent Shore hardness. The polyamide hard segments give PEBA filament a stiffer un-melted column than TPU at the same Shore reading, which reduces buckling under back-pressure. A PEBA 40D filament (~90A equivalent) prints reliably on Bowden hardware where a TPU 90A filament would buckle. This is operationally significant for multi-extruder systems with longer filament paths.

Print speed compounds the back-pressure constraint. A flexible filament that prints reliably at 20 mm/s may buckle at 40 mm/s under otherwise-identical conditions because the higher volumetric flow demands a higher melt back-pressure. The first calibration step on any new flexible filament is max volumetric flow at the target nozzle temperature — typically 4–6 mm³/s for softer grades, 6–10 mm³/s for 95A, up to 12 mm³/s for the harder 60D–72D grades. Start lower and walk up.

16.6 Bed adhesion: the over-grip problem

TPU, TPEE, and PEBA all adhere strongly to smooth PEI surfaces — strongly enough to damage the spring-steel sheet on removal of large or geometrically complex prints. The same over-grip problem documented for PC and PETG, amplified because elastomer surfaces deform during removal and create additional stress on the sheet. The standard mitigations apply: glue-stick release layer, PVP coating, dedicated build sheets engineered for elastomers, or substantially lower bed temperatures to reduce grip. Textured PEI grips less aggressively and is the practical default for routine TPU work; smooth PEI with a glue-stick release is appropriate for parts that need a glossy first-layer surface. CryoGrip Glacier is also documented as a successful cold-release surface for TPU; bed temperature 40–50 °C with no adhesive is the typical workflow. PEBA adheres less aggressively than TPU to PEI and typically releases cleanly without adhesive aids at 50–90 °C bed temperature — one of several ease-of-use advantages PEBA carries over TPU in production work.

16.7 Drying

TPU is moderately hygroscopic — typical saturation 0.3–0.8%, less than polyamides but more than polyesters. Moisture symptoms are characteristic and immediately recognizable: visible steam bubbles emerging from the nozzle tip during extrusion, audible popping in the melt zone, severe surface roughness on the printed bead, and substantial strength loss in the printed part. The Part I §3.5 drying table specifies TPU/TPE at 50–65 °C for 4–6 h, with the strong caveat that the upper temperature must stay below the Vicat softening point of the specific filament — softer grades (60A, 70A) deform irreversibly above 55 °C and spool layers can fuse together inside a hot dryer. Bed-style filament dryers running at 50 °C are safe for all grades; convection ovens require careful temperature monitoring on the soft-grade filaments.

TPEE has lower moisture sensitivity than TPU but the same surface-quality symptoms when wet. Drying at 65–75 °C for 6–8 h is standard. PEBA is the most hygroscopic elastomer in this chapter by virtue of its polyamide hard segments — which carry the same amide-group moisture behavior as the aliphatic nylons of Chapter 13. Saturation absorption runs 1–2% depending on the grade. Drying at 70–80 °C for 6–8 h is the standard before serious prints; dry-box storage during printing is essentially mandatory for opened spools. The higher safe drying temperature relative to TPU reflects PEBA's higher service temperature.

16.8 Process parameters (consolidated)

The table below consolidates the elastomer process windows from §16.5–16.7, Appendix A.3, and the Appendix B bench profiles into a single starting-point reference.

Parameter	TPU 60A–85A	TPU 90A–95A	TPU/TPE 64D+	TPEE (TPC)	PEBA (TPA)
Nozzle (°C)	220–240	220–250	230–260	230–250	225–250
Bed (°C)	40–50	40–60	40–70	50–70	50–90
Bed surface	textured PEI; CryoGrip Glacier at 40–50 °C	textured PEI; smooth PEI + glue-stick release	textured or smooth PEI	textured PEI or CryoGrip Glacier	smooth PEI — releases clean without adhesive
Chamber	open	open	open	open	open
Extruder	constrained-path direct drive (60–70A); direct drive mandatory ≤85A	direct drive preferred; Bowden workable at 95A	any	direct drive preferred	Bowden workable at 40D (stiffer un-melted column, §16.5)
Max volumetric flow (mm3/s)	4–6	6–10	5–12, grade-dependent (B.2 bench spool: 5)	6–12, hardness-dependent	6–10 (40D ≈ 90A equivalent)
Drying	50–55 °C, 4–6 h (below Vicat)	50–65 °C, 4–6 h	50–65 °C, 4–6 h	65–75 °C, 6–8 h	70–80 °C, 6–8 h

_{Table 16.4 — Elastomer starting print parameters (0.4 mm nozzle), consolidating §16.5–16.7 with Appendix A.3 and the Appendix B.2 bench profile (Siraya TPU 64D: 260 °C nozzle, 45 °C bed, 5 mm³/s — inside these windows). Flow ceilings follow the §16.5 buckling constraint and drop fast with softness; soft-grade drying is spool-deformation-limited (Vicat), not chemistry-limited. Retraction and part-cooling values are deliberately omitted — they are hardware- and geometry-specific enough that no family-wide starting value is honest; tune per-spool alongside the §23 calibration workflow. Per-spool calibration remains mandatory.}

16.9 Foaming elastomers

Foaming filaments use chemical blowing agents — additives that release gas (typically CO₂ or N₂) at elevated nozzle temperatures — to produce extruded beads with internal microvoid structure. The result is a printed part with a 30–50% density reduction in the elastomer grades (the rigid foaming-PLA end of the category reaches up to 65% — Chapter 6), softer feel even at equivalent base-polymer hardness, improved acoustic absorption, and reduced thermal conductivity. The foaming PLA category (colorFabb LW-PLA and equivalents) is the volume leader and is covered in Chapter 6. The foaming-elastomer category is smaller but functionally distinct: combining elastomer elasticity with foam compressibility produces a cushioning material with properties no rigid foaming filament can match.

The foaming mechanism is nozzle-temperature-driven. Below an activation threshold, the blowing agent is dormant and the filament extrudes at its nominal density. The threshold is vendor-specific — Siraya Tech's foaming line activates at roughly 225–240 °C, while colorFabb varioShore TPU foams across roughly 200–250 °C, with printed density adjustable by nozzle temperature across that span. Above the threshold, the agent decomposes and the foaming begins; foam expansion ratio increases with nozzle temperature up to a saturation point. The operational consequence: print parameters must be calibrated against the foaming response, not just for surface quality. A filament that extrudes at 1.0 effective flow rate at 220 °C may extrude at 0.5 effective flow rate at 250 °C because the same volume of solid filament has expanded into twice as much bead volume. Vendor-published process windows specify the target foaming temperature; the slicer flow rate (typically encoded as extrusion multiplier in the 0.5–0.7 range, vs the 1.0 baseline) compensates for the expansion.

Foaming-elastomer brand landscape. colorFabb varioShore TPU is the reference foaming-TPU product — it has defined the consumer category since its 2020 launch and is widely distributed via colorFabb, MatterHackers, and Amazon. Siraya Tech is the other visible supplier in the consumer-accessible foaming-elastomer niche, with foaming TPU products engineered for footwear midsoles, custom-fit cushioning inserts, vibration-damping mounts, and orthotic applications. The Siraya Tech foaming line is elastomer-based — Flex TPU Air, Roamr TPU Air HR, and PEBA Air — which are exactly the products relevant to this chapter. Pricing runs 1.5–2× equivalent unfilled TPU. Specialty European and Asian vendors carry foaming-TPU SKUs at industrial-tier pricing for footwear-prototype applications. Application fit: foaming elastomers are the right choice when the part will see cyclic compression loading (running-shoe midsoles are the canonical application), when reduced weight at retained softness matters, or when acoustic damping is a design goal. Avoid foaming elastomers when dimensional precision matters (the expansion ratio drifts per-spool and per-batch enough that mating-surface tolerances are challenging) or when sustained static compression is the load mode (foamed elastomers take a compression set faster than the equivalent unfoamed base material).

16.10 Brand landscape

The flexible-filament market segments by Shore hardness, by base polymer chemistry, and by the price/performance tier. Most major filament manufacturers offer at least one TPU product; specialty elastomer brands (NinjaTek, Recreus) compete on the soft end where general-purpose vendors struggle. PEBA filament is available from a smaller set of vendors — specialty lines from Fillamentum and 3DXTech, budget-tier PEBA 90A from eSun and SainSmart, and non-foaming PEBA 85A and 95A from Siraya Tech. Foaming elastomers are a two-supplier consumer market: colorFabb (varioShore TPU) and Siraya Tech.

Brand	Notable products	Distinguishing notes
NinjaTek	NinjaFlex 85A; Cheetah 95A; Armadillo 75D	US elastomer specialist; the 85A and softer grades are the consumer-tier benchmark; Armadillo bridges into rigid territory
Recreus	FilaFlex 60A; FilaFlex 70A; FilaFlex 82A; FilaFlex 95A	Spanish specialist; the only commercial 60A elastomer with a developed retail channel; constrained-path extruders mandatory at the soft end
Polymaker	PolyFlex TPU95; PolyFlex TPU95-HF; PolyFlex TPU90	Mainstream consumer pricing; TPU95-HF is the high-flow variant; broad color availability
Bambu Lab	TPU 95A; TPU for AMS	TPU for AMS is engineered specifically for constrained-path buffer-fed printing; standard 95A TPU is direct-drive only
colorFabb	varioShore TPU	The reference consumer foaming TPU, sold since 2020; printed density adjustable via nozzle temperature; widely distributed (colorFabb, MatterHackers, Amazon)
Siraya Tech	TPU 64D; Pro Flex 85A; Flex TPU Air, Roamr TPU Air HR, PEBA Air (foaming)	TPU 64D is the impact-modified rigid-elastomer offering for living hinges and snap-fits; the foaming-TPU products target midsole and cushioning applications
3DXTech	3DXLABS PEBA 90A; specialty TPU grades	US industrial line; the PEBA is an experimental R&D-line (3DXLABS) product, not a CarbonX SKU
Fillamentum	Flexfill PEBA 90A	Arguably the most accessible consumer PEBA; published TDS; European mainstream distribution
Forward AM Technologies (ex-BASF; Stratasys, 2025)	Ultrafuse TPU 64D; Ultrafuse TPU 85A; Ultrafuse TPU 95A	BASF Elastollan TPU resin base; documented mechanical envelope; industrial-tier pricing; no PEBA SKU in the Ultrafuse flexibles line
eSun, Sunlu, SainSmart	eTPU-95A; TPU 95A; various TPU 95A products	Budget tier; cosmetic and prototyping use; mechanical envelope variable
Specialty TPEE	Envalior (formerly DSM) Arnitel ID 2045; 3DXTech 3DXFLEX TPC (discontinued)	TPEE products at the consumer tier are sparse; Arnitel ID 2045 is the most accessible current product

_{Table 16.5 — Elastomer brand landscape (early 2026). The Recreus FilaFlex 60A product is essentially the only consumer access to printable Shore 60A elastomer in the FDM market — printing it successfully requires a constrained-path extruder and substantial hardware investment beyond general-purpose printers. NinjaTek and Polymaker dominate the 85A–95A consumer mainstream. Fillamentum Flexfill PEBA 90A and 3DXTech's experimental 3DXLABS PEBA 90A are the specialty consumer-tier entry points for polyamide-block elastomer, joined at the budget tier by eSun and SainSmart PEBA 90A and by Siraya Tech's non-foaming PEBA 85A and 95A; colorFabb's varioShore TPU is the consumer-tier reference for foaming elastomer applications, with Siraya Tech's foaming line covering the midsole and cushioning end.}

16.11 Application fit

Choose TPU when: the part requires flexibility, vibration damping, or rubber-like compression behavior at room temperature; abrasion resistance matters (TPU outperforms most other elastomers); the application sees brief exposure to oils or aliphatic solvents (polyester-based TPU resists these well, polyether-based less so); cost is constrained and the application tolerates the 80 °C continuous-service ceiling.

Choose TPEE when: the elastomer will see continuous service above 80 °C (engine-bay grommets, high-temperature gaskets, oven-adjacent dampers); creep resistance under sustained load matters more than maximum elongation; oil and fuel exposure is in scope (TPEE outperforms TPU on both).

Choose PEBA when: dynamic flex performance is the binding constraint (athletic footwear midsoles, sporting equipment, repeated-cycle mechanical springs); the part will see uncontrolled humidity in service (PEBA's hydrolytic stability substantially exceeds TPU's); low density matters (PEBA has the lowest density of the elastomer chemistries in commercial FDM filament form); the temperature range extends from below freezing through 70–90 °C continuous (~100 °C short-term in the stiffest grades); cost is justified by performance.

Choose a foaming elastomer when: the design goal is cushioning under cyclic compression (footwear midsoles are the canonical case); reduced weight at retained softness matters; acoustic damping is part of the application; dimensional precision is not the binding constraint (per-spool foaming expansion drift makes tight-tolerance mating surfaces challenging).

Avoid elastomer filaments when: the part needs precise dimensional tolerance (elastomers print with looser dimensional control than rigid polymers); multi-material printing with rigid filaments is required and the rigid material's process temperature exceeds the elastomer's Vicat point; the design loads the elastomer in compression with no relief geometry (elastomer compression set is 15–40% for solid grades (Table 16.3; foamed grades run higher) and degrades the application over time).

---

← Contents · ‹ Part VII — Polycarbonates · Part IX — Specialty engineering thermoplastics ›