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 plasticinjection 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.
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