Laser perforation of polyethylene terephthalate/polyethylene laminated film for fresh produce packaging application

The polyethylene terephthalate/polyethylene laminated film was perforated using a carbon dioxide (CO2) laser emitted at an infrared wavelength of 10.2 μm. Pulse durations were varied from 3 to 200 μs, which corresponded to the fluence from 5.5 to 369.8 J/cm2. Laser perforation process was irradiated on either PET side or PE side. With the increase of fluence, the surface deformation was observed to create microhole formation. The perforation threshold to create a microhole on the PET side was 74.0 J/cm2 and that on the PE side was 92.5 J/cm2. The microhole area and volume loss increased with the increment of fluence. Noticeably, the laser perforation on the PET side used up to 50 % less energy than the perforation from the PE side to create the same size through-microhole. Oxygen transmission rate (OTR) and carbon dioxide transmission rate (CO2TR) of the laminated film with single microhole increased with increasing microhole area. For packaging application, mixed vegetable salad was packed in a plastic tray and heat-sealed with a microperforated top lidding film. The steady state level of gas composition of 10 %–13 % O2 and 8 %–10 % CO2 was achieved in all packages, except the one without perforation. Film with OTR and CO2TR of approximately 23,616 and 17,952 cm3/m2.d, respectively, was clearly shown to create modified atmosphere condition in the package that could keep the mixed salad fresh for 9 days at 8 °C.