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Hi all, we are facing silver streaks issue in PVC molded fittings . we are doing the inhouse compounding and the compounded mix is pelletized and using for molding operation. we are predrying the pelletized material twice @80 degree celcius and the silver streaks issue is going. My question is it possible to accumulate moisture from the compounding operation. we are not storing material in warehouse , we are directly using it from pelletizer. Can anyone help.
PVC isn't hygroscopic so I've never seen it dried. I would bet one of your additives is carrying the moisture or its shear or residence generated. For shear, I'd expect a narrow area or sharp corner in the tool is degrading the resin as you inject it. BTW-Do you run this in a cold runner?
Rick
Maybe its the extensive drying you describe. Try to reduce it and check the result. ("Too much dry(ing) will kill you :)"
j
Hi Rick , we are running cold runner,initial investigation found that the hot mixing breather was blocked and the pelletizing barrel vacuum was not enough .Thanks
Single time drying unable to eliminate the silver streaks, whereas two times drying is eliminating the silver streaks effectively.still searching for the root cause.Thanks
Ok, tell us more about the process and equipment.
temperatues (setup)
plastification setup
residence time
inj. unit and machine inlet and outlet diameters.
tool runner system
pictures of problem
J