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Thread: PVC Moisture content

  1. #1
    Join Date
    Oct 2014
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    BH
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    8

    Post PVC Moisture content

    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.

  2. #2
    Join Date
    Aug 2011
    Location
    Upstate of South Carolina
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    701

    Re: PVC Moisture content

    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

  3. #3
    Join Date
    Jun 2014
    Location
    EU
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    125

    Re: PVC Moisture content

    Maybe its the extensive drying you describe. Try to reduce it and check the result. ("Too much dry(ing) will kill you "

    j

  4. #4
    Join Date
    Oct 2014
    Location
    BH
    Posts
    8

    Re: PVC Moisture content

    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

  5. #5
    Join Date
    Oct 2014
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    BH
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    Re: PVC Moisture content

    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

  6. #6
    Join Date
    Jun 2014
    Location
    EU
    Posts
    125

    Re: PVC Moisture content

    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

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