Short answer
Migration happens when soluble dyes, or pigments with soluble fractions, move into the contacting material, helped by plasticisers, heat, humidity and pressure. Use insoluble pigments, avoid dyes where contact with PVC, fabric or white laminates is expected, and run a contact test under conditions agreed with your customer.
Likely causes
Soluble dye or partly soluble pigment
Moves into any mobile phase it touches.
Plasticiser acting as carrier
PVC and some adhesives pull colour out of the PU.
Heat, humidity and pressure in storage or transit
Stacked, warm stock accelerates migration.
Light or white contact surfaces
Show even small amounts.
How to diagnose it
- Contact test: press the part against white PVC or fabric under light load at elevated temperature (for example 24 hours at 50–70 °C) and inspect for stain. Agree conditions with your customer.
How to fix it
- Switch to non-migrating pigment selections for the shade.
- Apply a barrier lacquer or in-mould coating.
- Reduce loading where shade allows.
How to stop it coming back
- List the contact materials in the shade brief.
- Make a contact test part of shade approval.
Where this problem appears most
Send us your batch number, PU system and a photo of the defect and our technical team will help you trace the cause. Ask a technical question.
