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Thread: Why Does Cling Film Cling ? (saran wrap)

  1. #1 Why Does Cling Film Cling ? (saran wrap) 
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    I am not sure where to start with this question -

    I am wanting to establish the factors which makes thin OPP (orientated polypropylene) bags stick together and whether changing the thickness of the material used for the bags would have any effect on how much the cling together -

    I have just delivered many many flat card items packed in 0.022mm thickness opp bags (as part of my job) and when I pull out a handful of the packages, they seem to cling a little (possible through static or surface tension, or slight moisture?) - The bags are so thin, that they ruffle a little too

    I am looking into many solutions to this - but my first port of call is the OPP bag -

    I was thinking that Cling Film / Cellophane wrap clings becuase it is thin - and thicker cellophane material does not cling so much -
    Is there a correlation between the material thickness and its clinginess (could there be a difference in the way static behaves with different thickness , or molecules, etc etc)- or do you know what other aspect I should be looking into to avoid this happening -

    Rather than babble on, any input at this stage would be appreciated///


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  3. #2  
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    Well, clearly you understand that the cling is caused by static electricity. The very thin sheets seem to be affected the most because of the gravity effect; that is, their light weight makes it easy for the small electrostatic forces to pick up several sheets at once.

    It is not clear from your question whether you are trying to do a scientific investigation or simply trying to reduce the annoyance of the static effect. If the latter, I would suggest the simple approach of buying a can of anti-static spray intended for fabrics and see how that can best be used in your work. It can go directly on your samples, or their container or the work surface.

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  4. #3 Re: Why Does Cling Film Cling ? (saran wrap) 
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    Quote Originally Posted by Lordgaz
    I am not sure where to start with this question -

    I am wanting to establish the factors which makes thin OPP (orientated polypropylene) bags stick together and whether changing the thickness of the material used for the bags would have any effect on how much the cling together -

    I have just delivered many many flat card items packed in 0.022mm thickness opp bags (as part of my job) and when I pull out a handful of the packages, they seem to cling a little (possible through static or surface tension, or slight moisture?) - The bags are so thin, that they ruffle a little too

    I am looking into many solutions to this - but my first port of call is the OPP bag -

    I was thinking that Cling Film / Cellophane wrap clings becuase it is thin - and thicker cellophane material does not cling so much -
    Is there a correlation between the material thickness and its clinginess (could there be a difference in the way static behaves with different thickness , or molecules, etc etc)- or do you know what other aspect I should be looking into to avoid this happening -

    Rather than babble on, any input at this stage would be appreciated///
    Salt air is good for static. The salt decreases the resistance of air. I grew up on the water and only got to see static when it was very, very cold outside and the baseboard heat ran constantly.

    I found out later that in other areas, people have static all the time.

    I noticed that Argon and helium in the air increase static greatly.

    You might try an aluminum work table. Aluminum has proven itself as a way to stop static in high speed cloth polishing work and machinery.

    Things in the field of aluminum tend to equalize in voltage.

    However in severe dry air, aluminum appears to be capable of conducting static electricity with an almost weak lightning like effect. However the lack of moisture was severe. And the magnetic field strong, as well as the friction present being strong.

    In aluminums defense it did not hurt permanently human flesh.

    You could always wear an aluminum foil hat, however I would be fearful of micro waves. Ha-ha.


    Sincerely,


    William McCormick
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  5. #4  
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    Saran (sp?) slicks to object because it is an inductive material, inductive meaning it doesn't transfer electrons yet it still holds a static charge. So if the saran wrap was negative like acetate strip for example, it would stick well to postive objects. If the object was also negative (like the saran wrap), it wouldn't be effective. To put it simply, saran works by static inductive charge.
    Si vis pacem, para bellum.
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  6. #5  
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    Saran also "works" because it has high friction, with excellent affinity for itself, and is elastic. But just off the roll, like the OP's problem, yeah the magic is in high static & thin sheets. That stack of sheets is the form of a capacitor (most caps are rolled not laid).

    Eliminate static then. The spray should work, but that seems sloppy. How about metal conductors? You can buy self-adhesive copper tape at electronics shops - a few runs into the depths of your container should do. Or maybe just sit the box atop grounded appliance (e.g. stove, refrigerator) for a while, if the static originated when sheets were collated.

    I think that how you handle the product will make a difference. You can discharge much static with your bare hands.
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