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How to discharge a clear plastic film roll ? : (

  1. Feb 1, 2013 #1
    Hello !

    Firstly, i'd like to say that I have nothing to do with physic - and everything I've learnt in school - has been forgotten and I really hope you can help me with a small problem I have ..

    I bought a roll of clear plastic film (100 m) one like this http://www.bizrice.com/upload/20120506/Clear_heat_shrink_plastic_film_pvc_wrap.jpg - for packing .

    After two weeks I noticed that the roll got charged ?! When I want to cut some film from the roll - the film itself seems to be like a magnetic sheet - If I pull the film and then release it- it will wrap back on the roll like a magnet - and is quite difficult to work with it.

    Any help would be gr8


    kind regards
    S
     
  2. jcsd
  3. Feb 1, 2013 #2

    mfb

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    You might charge the film by pulling it. You could test a higher humidity.
    I don't think electric charge is the main problem, however - if you rip it off, the film will try to roll itself as well. It is just the shape of the material.
     
  4. Feb 1, 2013 #3
    no is not the shape - as is just a thin film .

    Even after cutting a square meter from the roll - that square will tends to stick to my body , or to any wooden door etc .


    I will try to cut another square today and leave it on the side overnight - and i'll check in the morning if anything has changed .

    thanks a lot
     
  5. Feb 1, 2013 #4

    mfb

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    Oh, that size and effect. That is an electric charge, right.
     
  6. Feb 1, 2013 #5
    Put nearby a cable connected to earth (e.g. through a tap). A spark discharge should occur even without touching the roll with the cable. The length of the spark will be indicative for the potential difference (1 mm spark corresponds to about 3000 V).
     
  7. Feb 1, 2013 #6

    Vanadium 50

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    I don't think the plastic has a net charge. I think that when you pull it, the side you are pulling develops one charge and the side you are pulling away from develops the opposite charge.
     
  8. Feb 2, 2013 #7
    Even if there weren't net charge but only imbalance within the roll it should be equilibrated by connecting to earth.
     
  9. Feb 2, 2013 #8
    You could build some kind of foil dipenser and place a metal wire or several wires such that the foil passes by them when you unroll it.
    Does it matter if the foil gets wet? If not you could just put the whole roll into a tub of water and then unroll it there.
     
  10. Feb 2, 2013 #9
    Anti-static roll might suit you purposes, depending upon what you are doing with the shrink wrap.
     
  11. Feb 3, 2013 #10

    NascentOxygen

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    The static charge is usually a desirable trait, acting like adhesive, for wrapping up things in the kitchen. You might need to arrange that as you draw out the film it passes over conductive brushes so they can collect/equalize the charge from both sides. :grumpy:
     
  12. Feb 3, 2013 #11
    The foil is adhesive because of polyisobutylene that's mixed into the LDPE. It serves as a cling agent that makes the foil sticky. It has nothing to do with static charge.
     
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