Name both surfaces that touched

Packaging sample showroom of SamBound New Material Technology Company Ltd. (sambound.com).

A coefficient of friction applies to the surfaces sliding against each other. A printed exterior, an unprinted exterior region and the heat-seal face of a film can give different results against the same counterface. Even the unprinted region can carry a treatment or varnish, so describe the actual finish. Record which face was on the sled and which was on the bed, or specify the guide material if the film was tested against a solid surface.

Match the pair to the handling step

Consider an overwrap with a printed exterior and a heat-seal layer on the inside. In one operation the exterior runs against a guide. In a separate stack, the exterior of one cut piece may sit against the inner face of the next. Test and label those contacts separately using a defined orientation, load and speed. The report can then answer the handling question that prompted each measurement.

If a seal is also under review, assess it with an appropriate sealing test. Friction at the sealant face characterizes movement at that interface under the stated conditions.

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