Determination of Causes of Coefficient of Friction Increases in PE/PET Laminates Using Time-of-Flight Secondary Ion Mass Spectrometry, 2002 PLACE Conference Proceedings

The Coefficient of Friction (COF) of PE/PET laminates is critical to their performance in packaging applications. Occasionally, the COF of these films can unexpectedly increase when they are stored. The COF of the film is controlled primarily by the SLIP additives that have been deliberately blended into the film. In order to fully understand why a given film has an acceptable or unacceptable COF, one must identify the total SLIP content of the film, the location of the SLIP within the film, and the type of SLIP present in the film. Furthermore, since other components of the film may interfere with the SLIP, it is often necessary to fully characterize the film to identify the factors that alter the behavior of the SLIP. Several techniques are available for SLIP analysis, including extraction (coupled with FTIR, GC, HPLC and/or NMR), and Attenuated Total Internal Reflectance FTIR (ATR). However, these techniques are often insufficient to generate a complete picture in order to solve a COF problem. Time-of- Flight Secondary Ion Mass Spectrometry (ToF-SIMS) can be used to identify and quantify the SLIP present, map the distribution of the SLIP, and map the construction of the complete film. In this manner, this technique can be used to identify the root cause of the COF problem. In this case, the ToF-SIMS identified the root cause as mixing of the urethane adhesive used in the lamination into the PET layer. The mixed urethane/PET layer interacts with the SLIP at the surface to redistribute the SLIP into the mixed layer, reducing the COF of the film.