cracks of PVC after aging on AWG wire

Dear All,

I found small cracks on PVC with nylon that used in AWG wire after aging and flexibility testing. Some sample have cracks and others haven't although we are using same compound. Is there any justification to change the process such as preheating the copper or changing the type of copper itself?.

Please help!.
Basem

Hello Basem,

Firstly, you must remember that PVC is a mixture of materials and you have not told us whether or not you are manufacturing your own PVC with a very good machine such as a Kombiplast to ensure uniformity. Poor manufacturing practices can result in variances in properties.

Some other points you should remember.

1 - It is good practice to electrically preheat the copper conductor before it enters the crosshead.
2 - It is good practice to dry the PVC down to a -40C dew point in or just before the extruder hopper. Just recirculating hot air is not the answer as you are not drying the air and the moisture is going around and around.
3 - Changing to an alloy of copper has nothing at all to do with this plastics issue.