Hi, I’m a bit confused here, when a laminated 15 micron nylon/50 micron PE runs in our TRESIDE forming machine, powder will tend to build up on the triangle forming frame. But when using a thicker 70 microns PE with same materials and slip percentage, no buildups occurs. With the case of the PP slip that you mentioned above, as thickness increase we have to reduce slip concentration, but in this case the thinner gauge tend to powder compared to the thicker gauge. DO I NEED TO TEST THE COF VALUE OF THESE 2 FILMS?
p.s we are planning to get either extrusion coating machine or extrusion lamination machine. would you give me an idea what the difference between this two process. Actually we want to laminate printed OPP to VMPET without the bubbles problem, that’s why we are considering this process. What the best process for our requirement.
Thanks, Rakatin
Eldridge’s Reply:
Well the reason you need less slip in a thicker film is that the slip works by covering the surface and the thicker film caries more slip relative to the surface area. Another factor which is important is the saturation concentration for the film, For OPP this is about 600 ppm for erucamide. What the saturation concentration is for your polymer and slip agent needs to be determined to better control the loading in the thin and thick films. It would seem from your observations that the thinner film has a thicker slip layer on the surface than the thicker film and it might be well above the saturation concentration thereby forming a thicker slip layer which is scraping off on the former.
I would not check COF to determine the source of the problem but rather the concentrations of slip in both the 50 and 70 micron films, also the type of slip additive used if you are not making the films yourselves. I would also analyze the powder deposit to make sure it was slip and not low molecular weight PE from the film. This could be formed from extrusion conditions or perhaps from an over treatment of the film generating low molecular weight compounds on the film surface which abrade off the film onto the former.
In regards to your P.S., extrusion lamination is essentially the same process as extrusion coating except that the coating is trapped between two films for extrusion lamination while for extrusion coating; the polymer is the outer layer and usually a sealant material. Extrusion lamination allows the addition of thicker sealant webs than can be produced by extrusion coating.
Extrusion lamination also allows the production of thick laminations with less expensive PE replacing the more expensive OPP. It also aids in sealing the lap seal area from air leaks in the seal. It is very common for laminations of printed OPP to metallized films. I am not sure what your bubble problem is unless it is residual solvent from adhesive laminations or poor application or combination of the lamination.
I cannot answer what is best for your requirement because you have not defined what your requirements are.
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