Ask the advisor

Olefin block copolymers in running shoes

Olefin block copolymers — Dow's Infuse OBC family and the chemistry behind Nike's ReactX — sit between EVA and TPU on every important property axis. They're rarely the whole midsole; they're the blend partner that quietly makes a lot of modern EVA-branded foams feel livelier than they used to.

What olefin block copolymers actually are

Olefin block copolymers (OBCs) are polymers built from alternating "hard" crystalline polyethylene blocks and "soft" rubbery ethylene-octene blocks along the same polymer chain. Dow Chemical commercialized them in 2006 under the trade name Infuse, originally for high-end packaging and automotive applications. The chemistry is sometimes also called a polyolefin elastomer (POE) when the block structure is less pronounced.

The structural feature that matters for footwear is the same one that matters for PEBA: alternating hard and soft segments along one polymer chain produce a material that recovers shape better than a homogeneous polymer of equivalent stiffness. The hard blocks are crystalline and rigid (so the material holds its structure at body temperature); the soft blocks are amorphous and rubbery (so the material rebounds elastically when compressed).

Brands use OBCs three different ways. As a blend partner with EVA — ASICS FF Blast Plus, FF Blast Max, FF Blast+ Eco are all EVA/OBC blends, typically in the 60/40 to 70/30 EVA/OBC range. As a stand-alone elastomer — Nike's ReactX (a TPE in the olefin-elastomer family) and On's Helion (also EVA/OBC). And as a sustainability lever — OBCs can be supplied as bio-based grades, which is why "Eco" branded foams (FF Blast+ Eco, Helion) often show up on this page.

Related: Most catalog shoes that use OBCs use them blended with EVA; the EVA page covers the blend's typical formulation. PEBA is the higher-tier alternative when energy return is the priority over durability.

Why olefin block copolymers matter for runners

The honest case for OBC content in a midsole is that it splits the difference between EVA and TPU. Pure EVA has predictable durability but lower rebound. Pure TPU has higher rebound but is heavy. An EVA/OBC blend at the right ratio gives you EVA's density and durability with measurably more rebound resilience than EVA alone — Dow publishes Infuse rebound figures in the 60–70% range vs 55–65% for high-grade footwear EVA.

The Run Testers' comparison of the older all-EVA Novablast 4 vs the EVA/OBC Novablast 5 is the cleanest A/B test in the catalog for this. Same shoe geometry, same brand, the only meaningful chemistry change is the OBC content — and the Novablast 5 is described as bouncier, more lively, slightly heavier, and durable-feeling. That difference is roughly what an OBC blend buys you over plain EVA.

The honest tradeoffs: OBC is more expensive than EVA, less expensive than PEBA, less expensive than TPU. The energy-return gain over plain EVA is real but smaller than the gain PEBA delivers. And OBC blends are still bound by EVA's pace sensitivity — the foam wakes up at faster paces and feels less distinctive at conversational pace. For pure marathon racing, PEBA is still the right answer. For everything else, an EVA/OBC blend is increasingly the daily-trainer default.

The "ReactX" branding deserves its own note. Nike's ReactX is a TPE (thermoplastic elastomer) closely related to the OBC family — Nike has not published the exact composition, but the property profile and processing description match an olefin-family elastomer. It's the foam in the Pegasus 42, paired with a full-length Air Zoom unit; in the Pegasus Premium and Structure Plus it sits underneath a ZoomX (PEBA) top layer.

Featured shoes built on olefin blends

ASICS Novablast v5

FF BLAST MAX (EVA/OBC blend)

The reference EVA/OBC blend daily trainer. ASICS' FF Blast Max in the Novablast 5 is roughly 70% EVA / 30% OBC by weight — Dow's Infuse is the OBC family they use. The Run Testers and Doctors of Running both treat the Novablast as the bouncy daily trainer to beat at $140; the OBC content is most of the reason it feels livelier than a pure-EVA equivalent.

ASICS Gel-Nimbus v28

FF BLAST PLUS (EVA/OBC bio-based blend)

OBC blend in a max-cushion context. FF Blast Plus (eco bio-based grade) gives the Nimbus 28 a softer, more plush feel than the all-EVA Nimbus 27. Believe in the Run notes the difference is felt on long easy runs more than tempo work — exactly where a max-cushion shoe earns its keep.

On Cloudmonster v3

Helion (EVA/OBC) with triple CloudTec layers

Helion is On's EVA/OBC blend, used as the structural foam under all the visible CloudTec pods. EDDBUD describes the Cloudmonster 3 as the most "normal-feeling" Cloudmonster yet — the OBC content adds rebound that the previous all-EVA Helion lacked.

ASICS Gel-Kayano v32

FF BLAST+ ECO (EVA/OBC bio-based blend)

OBC in a stability shoe. FF Blast+ Eco is a bio-based EVA/OBC blend; ASICS pairs it with the 4D Guidance System under the rearfoot. Doctors of Running treats the Kayano 32 as the modern stability reference — the OBC blend is durable enough for high-mileage runners while still feeling soft at touchdown.

Nike Pegasus v42

ReactX (TPE) + full-length Air Zoom unit

ReactX as a stand-alone olefin-family midsole. Nike's ReactX is a TPE / olefin-family elastomer, used in the Pegasus 42 paired with a full-length Air Zoom unit. Run Testers describes the new Pegasus as the most cushioned Pegasus yet — ReactX hits a different point in the energy-return-vs-durability tradeoff than EVA blends do.

These five span the OBC application range — bouncy daily (Novablast 5), max-cushion (Nimbus 28), max-cushion alternative (Cloudmonster 3), stability (Kayano 32), and the standalone TPE case (Pegasus 42).

Every shoe in the catalog using olefin blends

12 shoes. Includes EVA/OBC blends and stand-alone olefin-family elastomers (ReactX, Helion).

Sources

Methodology. Chemistry sourced from manufacturer technical data and peer-reviewed work. Shoe-level commentary is summarized from named reviewers (Doctors of Running, Believe in the Run, The Run Testers, Kofuzi, EDDBUD) — every shoe page linked above carries the original verdicts with source links. Never sponsored, never paid placement.