Delamination

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. lists causes and solutions for delamination.

Causes:

1. One of the main causes 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

2. 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

3. 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

4. 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

5. Too hot a mold temperature can cause delamination, causing the skin to stick on the hot mold surface and separate

Solutions:

1. Recommended drying temperatures and times

should be used based on material supplier

recommendations

2. Better mixing and better melt uniformity as

well as increasing melt temperature is needed to

prevent delamination in this case

3. Better screw design will also help in providing

improved melt uniformity

4. Reducing pack pressures will prevent this

buildup of excess material from forming

5. Reducing mold temperature will eliminate this

condition