Abstract:

In this paper， five methods of sampling pretreatment were adopted to obtain the cross section of a commercial food⁃packaging composite film， and its layer structure and material compositions were analyzed by using scanning electron microscopy （SEM）， energy dispersive X⁃ray spectroscopy， and Fourier⁃transform infrared spectroscopy. The results indicate that the composite film was composed of five layers， including a polyethylene terephthalate （PET） layer， an inorganic pigment/polyurethane （PU） adhesive/aluminum⁃metallized layer， a PET layer， a PU adhesive layer， and a polyethylene layer in sequence. By observing the cross sections obtained from five sampling pretreatment methods using SEM， it was found that the composite film showed a small layered cross section when sampling with the steel and diamond knifes of an ultra microtome or an ion milling device， exhibiting an ideal morphology with a well⁃defined layer structure. In summary， an appropriate method can improve the successful rate greatly for obtaining an ideal film cross section. This is very significant for the quality inspection as well as the research and development of ultra⁃thin metal⁃coated multilayer films.

Key words: food?packaging composite film, scanning electron microscope, Fourier transform infrared spectroscopy, Ion grinding device, film cross section