During the operation of an extruder in making thin-walled tubing, several defects have been encountered that appear to be small globules of resin. Investigation of these globules reveals that they will soften but not melt when heated. Explain what these globules might be and suggest two possible remedies for eliminating them
What will be an ideal response?
The globules are likely crosslinked resin that has, for some reason, been created within the extruder. One likely cause is that the extruder may be overheating the resin, thus causing some of the material to crosslink. A solution for this would be to lower the temperature. Another solution would be to add thermal stabilizer additive to the resin which could also prevent this crosslinking from occurring. Another cause of the formation of crosslinked material could be non-streamlined flow in the die. This can be investigated by stopping the extruder and carefully examining the die to see if material seems to be hanging up in some location. If that is the case, the die should be smoothed.
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