Supercritical Foam for Insoles: TPEE, TPU, PEBA & EVA Compared

Supercritical foaming can turn TPEE, TPU, PEBA and EVA into lightweight cushioning foams - but which is right for your footwear or insole project? The answer depends on the formulation, foam structure and balance of cushioning, durability, fit and cost.

This guide compares the four material families and explains what brands should evaluate before production, drawing on research and Datong & Bangni’s approach to OEM/ODM insole development.

Supercritical foaming is a manufacturing technology, not a polymer type. “Supercritical foam” describes the resulting foam, while EVA, TPU, TPEE and PEBA identify the underlying material families.

Supercritical foaming uses a physical blowing agent, commonly carbon dioxide or nitrogen, under controlled temperature and pressure. The fluid dissolves into a suitable polymer formulation before expansion is triggered.

For example, Trexel’s MuCell® technology introduces precisely controlled amounts of supercritical fluid into molten polymer and mixes them into a single-phase solution. This provides the starting point for creating a microcellular structure. Source: Trexel—MuCell® Technology

When the polymer–fluid mixture experiences a controlled pressure reduction, small cells begin to form a process called nucleation. These cells grow as the dissolved blowing agent separates from the polymer. Their growth is controlled, and the structure is stabilized to produce foam.

Trexel describes this sequence in its injection process: cell nucleation begins as the mixture enters the lower-pressure mold cavity, followed by controlled cell growth. The resulting cellular structure reduces density compared with the unfoamed material.

Different manufacturing routes can produce supercritical foams:

• SCF injection foaming: The blowing agent is introduced during polymer processing, and the mixture is injected into a mold where cells form and expand.
• Batch or autoclave foaming: Material is treated with pressurized fluid in a vessel. Controlled changes in pressure and temperature induce foaming, with further shaping or finishing where required.

Research published in Polymers describes two-step batch foaming assisted by supercritical CO₂, illustrating that SCF processing is not limited to injection molding. The appropriate route depends on the formulation, desired foam structure and component design.

Buyers should distinguish between foam sheets or shaped components and expanded beads that are subsequently joined into a component.

BASF’s Infinergy® is a commercial example of expanded TPU bead technology used in footwear. However, E-TPU means expanded TPU; the designation alone does not specify every processing condition or mean that all SCF TPU is bead foam.

For an insole project, confirm the material grade, foam structure, component format and relevant processing requirements. These details help determine how the foam can be integrated with the top cover, support components and overall geometry.

A polymer name alone does not define the finished insole. Material selection must be followed by evaluation of the complete construction.

Brands are looking for ways to combine lower weight, responsive cushioning and repeatable manufacturing. SCF offers additional ways to tune foam structure, but results depend on the material and production system.

One commercial example is Huntsman’s SMARTLITE® SCF 280 TPU, announced in September 2025 for running and lifestyle midsoles. Huntsman reports up to 64% rebound, alongside an emphasis on durability and manufacturing automation. This is a supplier-reported value for a named technology, not a benchmark for all TPU foams or a direct measure of running performance.

The development options also extend beyond pure-polymer comparisons. Arkema’s Pebax® EVA+ compounds are designed for footwear midsoles and compatible processing routes, including SCF autoclave EVA foams. Their existence highlights an important sourcing consideration: commercial solutions may use blends rather than a single polymer.

For buyers, the opportunity is to specify a useful combination of properties rather than chase one headline number:

• Lower component weight within the required thickness and geometry.
• Cushioning and recovery suited to the intended activity.
• Consistency after repeated loading and environmental conditioning.
• A production route that fits the target volume, tolerances and cost.

Environmental claims require the same discipline. Huntsman’s recycling statement for its named SCF technology explicitly assumes an end-of-life take-back program. Physical foaming should therefore not be treated as automatic proof that a finished, multilayer insole is recyclable or has a lower carbon footprint.

There is no universally best supercritical foam. Resin grade, blends, foam density, cell structure, thickness and processing can all change the result. The following table is a material-shortlisting guide, not a measured ranking or a set of purchasing specifications.

This shortlist draws on commercial footwear materials and processing information from Arkema, BASF and Tien Kang, together with research on TPEE foam shrinkage. Each candidate still needs validation in the intended insole.

Compare like with like. Ask suppliers to identify the test method, specimen thickness, conditioning, loading conditions and hardness scale behind their numbers. Rebound measured in one test should not be ranked directly against a different energy-return measurement.

Likewise, separate compression set from fatigue. Compression set describes residual deformation after a defined compression and recovery procedure; fatigue testing examines changes through repeated loading. Both belong in the development discussion, but they answer different questions.

For costing, compare the complete insole: foam, top cover, support components, adhesive, processing, tooling allocation, yield and inspection. A lower resin price does not establish a lower finished-product cost.

TPEE gives development teams another material route to evaluate alongside TPU, PEBA and EVA. The useful question is whether a specific TPEE foam can meet the product brief at the required geometry, durability and cost.

Its processing behavior deserves attention. A 2022 paper in Polymer investigated molecular-chain relaxation in the shrinkage of TPEE foams produced with supercritical CO₂. This makes dimensional stability a relevant development question, rather than a property buyers should assume from the TPEE label.

For an insole brand, the practical checks are:

• Does the foam maintain the required dimensions after conditioning?
• Does the selected thickness provide useful cushioning without compromising shoe fit?
• Does the structure remain stable after repeated compression?
• Do the top cover and other layers remain securely bonded?
• Does the finished insole meet the target feel and cost?

These questions give TPEE a fair evaluation without assuming it must outperform PEBA or TPU. They also reduce the risk of selecting an impressive material sample that becomes difficult to integrate into a repeatable product.

Datong & Bangni’s role is to develop the insole around the selected material: aligning cushioning with geometry, layer construction and validation before the specification is approved for production.

Commercial footwear applications extend beyond racing. Arkema identifies road and trail running, hiking, approach shoes and certain safety-shoe applications for its Pebax® EVA+ compounds. These are application-specific solutions, not evidence that every grade suits every footwear category.

For insole development, the priorities should change with the use case:

These are proposed development priorities, not claims that SCF automatically delivers each outcome.

A removable insole also occupies a different role from a thick midsole. Its performance depends on available shoe volume, surface materials and any supporting components. Whole-shoe running studies should therefore guide testing questions, not become percentage-improvement claims for an insole.

Brands can explore Datong & Bangni’s sport insoles, work insoles and custom insole development as starting points for an application-specific brief.

Start with the intended product and work toward the material specification. Asking only whether a manufacturer can use TPEE or PEBA leaves important performance and production questions unanswered.

Define the product brief. Specify the activity, shoe type, target user, available thickness, desired feel, support requirements, size range, volume and target finished-insole cost. Include a reference product where useful.

Compare prototypes under consistent conditions. Evaluate candidate materials in comparable insole constructions. When geometry or layers change, record those differences so that the resulting performance is not attributed solely to the polymer.

Learn more: Arch Support Shell Materials Compared

Agree on acceptance criteria before bulk production. A practical validation plan should cover:

Record test conditions, recovery time, pass/fail limits and sampling requirements. Retain approved reference samples and document any material or process substitutions. This gives purchasing, engineering and quality teams a common basis for accepting production.

For Datong & Bangni, SCF is a material option within OEM/ODM insole development. Material selection, structural design, sampling and in-house laboratory testing are brought together to evaluate the finished insole and address risks before scaling.

The right supercritical foam is the material-and-process combination that meets the finished product’s requirements. The purchasing decision should reflect cushioning, fit, performance retention and total cost together.

Developing a new sport, work or everyday insole? Discuss your OEM/ODM project with Datong & Bangni. Share your application, target thickness, desired cushioning and support, testing requirements and expected volume to begin defining the right construction.