Choosing TPU hardness for injection molding requires balancing flexibility, compression, abrasion, tear, temperature, chemical exposure, bonding, and part geometry. Shore hardness is a useful starting point, not a complete specification for a finished part.
Translate the application into requirements
- Define deflection, grip, sealing, rebound, compression set, wear, tear, and load at the actual service temperature.
- Check exposure to oils, water, cleaning agents, UV, humidity, and repeated flexing.
- Specify the test method, direction, sample conditioning, and time scale for hardness and mechanical results.
Consider molding behavior
- Compare grade chemistry, flow, shrinkage, drying needs, melt stability, color, and demolding behavior.
- Review wall thickness, flow length, gates, vents, cooling, ejection, and any substrate for overmolding.
- Do not assume two grades with similar hardness will have the same adhesion, process window, or long-term performance.
Validate the chosen grade
Trial the exact grade, color, lot, and mold. Inspect dimensions, surface, adhesion, elasticity, compression, wear, and assembly. Document the approved grade and substitution rules so a hardness change does not silently change product behavior.
Plan the next step
Share your part, resin, annual volume, critical dimensions, finish, and timing with the Cavity Mold team through our contact page. We can review the manufacturing risks and recommend a practical next step.
Related Cavity Mold resources
- Injection mold engineering services
- Plastic injection molding services
- Injection mold making services
- Contact Cavity Mold
Technical references
- Avient TPE injection molding guide
- BASF Elastollan TPU processing recommendations
- Covestro TPU processing technology
Choose TPU hardness from function
Hardness is a useful starting point for TPU selection, but the molded part must also meet compression, tear, abrasion, rebound, temperature, chemical, grip, and assembly requirements. Define the behavior before selecting the label.
| Decision | What to check | Boundary |
|---|---|---|
| Compression and recovery | Define load, deflection, dwell, temperature, and recovery time. | A hardness value alone does not describe long-term compression behavior. |
| Flex and tear | Review bend radius, tear initiation, edge geometry, and repeated movement. | Sharp corners and thin sections can dominate failure. |
| Abrasion and grip | Define surface contact, friction, wear, and contamination environment. | The best grip grade may not be the best appearance or processing grade. |
| Processing and assembly | Check flow, mold release, bonding, overmolding, and cycle requirements. | Connect material behavior to the actual tool and process. |
TPU selection checkpoints
- Write the functional load and environment.
- Screen grade data under relevant conditions.
- Mold a representative geometry, not only a test plaque.
- Approve hardness together with the other acceptance criteria.
Discuss the requirement in engineering and include the selected grade and test boundary in the RFQ.