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Impact of film thickness on COF

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Q. Why does the thickness of a film change the COF value?

A. Effect of gauge on COF: Slip is added to the polymer and dispersed uniformly throughout the melt. The majority of the slip then migrates to the surfaces and reduces the COF. Since most of the slip ends up on the surfaces, the important measurement is how much slip was in that volume (area x thickness) of the film. Thicker films have a higher volume and thus, more slip ends up on the surface. The net result is that the COF will be lower for thicker films of a given formulation. Film manufacturers will typically reduce the slip content of a product as they produce thicker films to offset the volume effect.