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Delamination in plastic injection parts

Delamination is a condition that exists when the surface skin of a molded part can be physically separated from the part which can lead to a reduction in mechanical strength . Here are some causes and solutions below for Delamination of plastic injection parts.

One of the main cause of delamination is incompatibility of mixed materials due to material contamination. For example, nylon is contaminated or mixed with polyethylene, delamination will take place, due to the difference in the rheological properties of the two materials. Solutions: Recommended drying temperatures and times should be used based on material supplier recommendations.

Contamination can occur from moisture in material that has not been dried sufficiently. Bubbles or blisters are formed and trapped on the part surface in a fully packed cavity, and the skin formed by the trapped moisture can be separated. Solutions: Better mixing and better melt uniformity as well as increasing melt temperature is needed to prevent delamination in this case.

Nonuniform melt temperatures are yet another cause of delamination. Colder material will flow much slower than the hotter material, causing the cold skin to separate from the hotter forming skin. Solutions: Better screw design will also help in providing improved melt uniformity.

High packing pressures can cause delamination at the gate. When a object shrinks away from the gate or sprue bushing, high packing pressure can force excess material into the gap between the object and mold cavity. A thin layer of material is formed on the surface of the part. Upon workpiece ejection, this thin layer can separate and delaminate. Solutions: Reducing pack pressure will prevent this buildup of excess material from forming.

Previous: Injection molds
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