Painting Surface
TPU
Thermoplastic polyurethane (TPU) is a flexible plastic used in phone cases, films, footwear, seals, and protective parts. Its elasticity and solvent sensitivity make coating selection highly product-specific.
TPU paint compatibility
Flexible coatings can work when they are approved for the exact TPU grade, while rigid films and aggressive solvents can cause cracking, swelling, or poor adhesion.
| Paint | Compatibility | Preparation | Primer or ground | Finish | Guide |
|---|---|---|---|---|---|
| Flexible specialty coating | Best when explicitly approved for the TPU grade and expected flexing | Clean and dry the surface and remove mold-release or processing residue without using an incompatible solvent. | Use only the adhesion promoter or primer specified by the coating manufacturer. | The coating must remain flexible enough for the part's normal deformation. | — |
| Paint markers | Formula-specific | Clean the surface and test adhesion and flexibility before committing to the design. | Usually product-specific. | Best on lower-flex areas where handling and abrasion are limited. | — |
| Spray paint | Use only when the exact aerosol system approves the TPU | Avoid assuming that a general plastic spray is compatible; some solvents can swell or damage TPU. | Product-specific. | Rigid aerosol films can fail as flexible TPU bends or stretches. | — |
| Acrylic paint | Limited and formula-specific | Test first on the actual TPU because hardness, chemistry, and additives vary between grades. | A compatible flexible primer or additive may be required. | Ordinary acrylic films may crack or peel on highly flexible TPU. | — |
Sources: Covestro TPU structure and properties and Covestro TPU chemical resistance.