The structure and packaging properties of films made by Poly(lactic acid)/ lactide grafted Zeolite

Abstract

Graft modification is used to achieve homo-dispersion of zeolite in the PLA resin. First zeolite was treated with acid and ultrasound, and then it was modified by grafting lactide onto it. XRD and FTIR demonstrated that the in situ grafting reaction of lactide to the surface of zeolite took place at 140 °C, under the conditions of mass ratio of 4-dimethylaminopyridine, lactide and zeolite of 2:1:1 and reacting for 24 h. The particle size distribution proved that the modified zeolite particles were significantly smaller, and TGA proved the highest grafting rate under the conditions of 4-dimethylaminopyridine, lactide, and zeolite with the mass ratio of 2:2:1 for 24 h. Finally, the PLA matrix was filled with graft-modified zeolite and epoxidized soybean oil was used as a plasticizer to prepare modified PLA blown films. The results showed that lactide grafted zeolite could be more homo-dispersed in the PLA matrix, and the tensile strength of the composite film was improved to 65.73 MPa, the elongation at break was improved to 35.33 %, the crystallinity was improved to 46.91 %, and the thermal stability of the composites was also improved compared with that of pure PLA. The water vapor permeability of the composite film became 2.73 × 10−7 g·m/(m2·h·Pa), and the oxygen permeability of the composite film became 6.63 × 10−7 cm3 cm/(cm2·s·Pa), which can be used as modified atmosphere packaging film.