In Pursuit Of The Perfect Injection Moulded Part 9 – Delamination


If you find thin layers on the surface of a moulded part are easily separating or peeling off the underlying material, you’re seeing a moulding defect called delamination. Delamination is a defect characterised by a flaking surface layer, similar to what you’d commonly find on flake mica. This is generally regarded as a relatively serious defect because it reduces the strength of the component.

Causes and prevention of delamination in injection moulding

In Pursuit Of The Perfect Injection Moulded Part - Delamination

The most common cause of delamination is contamination of the resin pellets or other base material with a foreign material. Flaky separation results when the two materials cannot properly bond to each other. For example, you might combine a common base plastic like acrylonitrile butadiene styrene (ABS) with an incompatible plastic, such as polypropylene (PP). The resulting loss of strength of the material would be very dangerous if your part is intended for a safety-critical use.

Aside from material fed into the hopper, the contaminant could also be any excess release agents coating the mould for easier component separation. Excess moisture on the material, due to improper drying prior to use, can also cause delamination. Consider the following corrective actions to prevent recurrence if you discover delamination affecting your moulded parts:

  • Increase the mould temperature or pre-dry the material properly if excess moisture is an issue
  • Ensure workers are properly storing and handling the resin pellets or base material to prevent contamination
  • Consider redesigning the mould with a focus on the injection nozzle to limit your dependence on release agents

Injection moulding defects caused by poor mould design or maintenance

Defects can be introduced into moulded products by issues with the mould tooling itself. Certain defects are likely to occur when the mould is poorly maintained or designed. Especially in the latter case, these defects can be difficult or costly to address in future production runs when it’s necessary to completely overhaul the mould.

Patterson & Rothwell are a Plastic Injection Moulding Company based in the North West of England, UK producing goods for many business sectors. Our ethos is to offer our customers a professional yet flexible approach and of course provide attention to detail at every stage. Please contact us if you wish to discuss any Plastic Injection Moulding Project.