Nd:YAG Laser Perforation of Plastic Films for Enhanced Breathability

Abstract

This study focused on investigating the Nd:YAG laser perforation process of several common plastic films including biaxially-oriented polypropylene (BOPP), biaxially-oriented polyethylene terephthalate (BOPET) and low density polyethylene (LDPE) films. Films were perforated under various pulse energies of 50, 150 and 250 mJ and with pulse duration of ~10 ns and pulse repetition of 1 Hz. It was found that, BOPP, BOPET and LDPE films could be perforated using our developed Nd:YAG laser perforating system. Perforation width or diameters of all films increased with increasing pulse energies. Observed perforations were different among the three film types. For instance, at the pulse energy of 150 mJ, average microperforation diameters of BOPP, BOPET, and LDPE were 51.9, 57.5, and 31.0 microns, respectively. Overall results clearly demonstrated that a Nd:YAG laser perforation process used in this study was effective in developing breathable packaging films with tailored oxygen permeation property. Commercial BOPP films containing 200-1,400 micro-perforations/m2 (average perforation diameter of  50 µm) showed a significant improvement in oxygen transmission rates (OTR) of 25-700% over that of the regular BOPP. Very high OTR films of 16,000 cc/m2.day could be effectively produced for the micro-perforated BOPP, where OTR values of close to 20,000 cc/m2.day was obtainable in the case of BOPET films.