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

Abstract

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 250 mJ where the pulse duration and pulse repetition were kept constant at 10 ns and 1 Hz, 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 0.5 wt% 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/m2 (hole diameter of ~100 µm) 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/m2 and perforation diameter of 100 µm, 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 ~40–300 µm 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 © 2014 John Wiley & Sons, Ltd.

Effect of biaxial‐simultaneous stretching conditions on OTR and CO2 permeation of CO2 laser perforated poly(lactic acid) film

“…Microperforation is one of the techniques for increasing the gas transmission rate of packaging films. The O 2 , CO 2 , and ethylene gases can flow in and out of the packaging through the microholes, by which the undesirably low level of O 2 and high level of CO 2 in the package headspace can be avoided …”

“…Diameter of perforated microholes is normally less than 250 μm . As for gas molecules, the size or the mean free path of O 2 , CO 2 , and ethylene gases is in the range of nanoscale, which is smaller than the size of microhole.…”

“…The most efficient and practical method for making microperforated packaging is using lasers . Recently, laser applications have grown significantly in plastic industries because it is now possible to achieve production with a superior quality finishing along with greater process reliability.…”

“…and material parameters (ie, types of materials, thickness, types of additives, thermal conductivity, heat capacity, crystalline morphology, molecular chain orientation etc.) . There are several studies in the literature addressing a study of lasers interacting with polymer materials .…”

“…There are several studies in the literature addressing a study of lasers interacting with polymer materials . However, only a few works reported the production of a breathable packaging film by laser . Studies on the relationship between the high‐order structure of films and laser perforation behavior have rarely been reported.…”