Surface layers separating and peeling off. Weak bonding between layers caused by impurities, incompatible colorant, moisture or excessive shear.
Surface delamination is the part surface separating in thin layers; when lifted with a fingernail it comes off like a skin. It almost always comes from two materials not having mixed: different polymers mixing through contamination, or moisture and additive incompatibility. It is not a cosmetic defect; it spoils the mechanical integrity of the part.
A wrong diagnosis leads to turning the right parameter in the wrong direction. This defect can be confused with the ones below; the right-hand column gives the practical way to tell them apart.
| Confused with | How to tell them apart |
|---|---|
| Glass Fiber Marks | Glass fiber marks are feather-like light-colored lines on the surface and cannot be lifted off. With delamination the surface layer physically separates. |
| Plate-Out | Plate-out leaves deposits on the mold surface and appears as roughness on the part. Delamination is the separation of the part's own surface layer. |
When polymers that are not chemically related mix, the layers do not fuse. PP with PA, POM with many other materials are typical examples. Even a small amount of contamination can create separation at the surface; the whole line needs to be cleaned.
Trace the chain backward: the machine hopper, the dosing unit, the dryer hopper, the conveying line and the material container. It is the same map as the contamination points in a color change; the subject is covered in the color and material change article.
Yes. Because even a small amount of contamination can create delamination, the machine hopper, dosing unit, dryer hopper and conveying line must be cleaned together. Cleaning only the screw is often insufficient.