Microperforation of Three Common Plastic Films by Laser and Their Enhanced Oxygen Transmission for Fresh Produce Packaging

Three different plastic films of biaxially oriented polypropylene (BOPP), biaxially oriented polyethylene terephthalate (BOPET) and low-density polyethylene (LDPE) were perforated using Nd-YAG laser. Effects of laser pulse energy were examined by varying energies from 50 to 250mJ where the pulse duration and pulse repetition were kept constant at 10ns and 1Hz, respectively. It was found that perforation diameters of all films increased with increasing pulse energies. Observed perforations were different among the three film types. Explanation was contributed to material inherent property and its interaction with laser. Incorporation of an inorganic filler (i.e. silica based anti-blocking agent used in packaging film) of 0.5wt% into the LDPE films (0.5Si-LDPE) could improve perforation performance for LDPE. This was attributed to an increased thermal diffusivity of the 0.5Si-LDPE film. Commercial BOPET and BOPP films containing 97 microholes/m(2) (hole diameter of similar to 100 mu m) showed an improvement in oxygen transmission rates (OTR) of 18 and 5 times that of the neat films without perforation. In the case of perforated 0.5Si-LDPE films having similar perforations of 97 microholes/m(2) and perforation diameter of 100 mu m, a two-fold increase of OTR was obtained. Gas transmission rates of the microperforated films were measured based on the static method. Measured OTR and CO2TR values of the three films with varying perforation diameters in a range of similar to 40-300 mu m were compared and discussed. Overall results clearly indicate that perforation by laser is an effective process in developing breathable films with tailored oxygen transmission property for fresh produce packaging. Copyright (c) 2014 John Wiley & Sons, Ltd.