Evaluation of oriented poly(lactide) polymers vs. existing PET and oriented PS for fresh food service containers

Abstract

Poly(lactide) (PLA) polymers have garnered increasing attention in the last few years as food packaging materials because they can be obtained from renewable resources; their production consumes quantities of carbon dioxide; they can be recycled and composted; and their physical and mechanical properties can be tailored through polymer architecture. As a consequence, PLA is becoming a growing alternative as a ‘green’ food packaging material. PLA's optical, physical and mechanical properties have been compared to those of polystyrene (PS) and polyethylene terephthalate (PET), although studies comparing and showing the actual performance of PLA, PS and PET plastics containers are scarce. The purpose of this study was to investigate and compare the role of PLA in package sustainability for the food service industry. Two of the commonly used materials to make containers to package fresh food, PET and oriented polystyrene (OPS), were compared with oriented PLA (OPLA) and OPLA with 40% recycled content from the industrial trimming process. The recycled OPLA provides an opportunity for full material utilization and lower costs. This study involved a number of tests to quantify the physical, mechanical, barrier and compatibility properties that would affect the selection criteria for containers to be used for food service applications. Based on the data collected, OPLA, OPLA + 40% regrind, OPS and PET performances were evaluated. Exposure of the four materials to vegetable oil and weak and strong acids show a minimal reduction in the performance of these polymers. At ambient temperature, PET has the highest impact resistance, followed by OPLA, OPS and OPLA + 40% regrind. In terms of barrier properties, PET shows the highest oxygen barrier, followed by OPLA, OPLA 40% recycled content, and OPS. Thus, OPLA and OPLA with 40% recycled content can be used for fresh food applications as well as OPS and PET, and in many situations it performs better than OPS and PET. Copyright © 2005 John Wiley & Sons, Ltd.