Geometrical evaluation of thermoformed bioplastic tray packages

Abstract

Plastics that are renewable and biodegradable have become increasingly popular in the quest for greener and more sustainable food packages. These so-called bioplastics are designed to replace traditional petrochemical polymers with renewable natural resources. To be a viable alternative to these oil-based resources the material must be successfully integrated into existing mass-manufacturing processes that transform material sheets into three-dimensional products. The purpose of this study was to examine the effect of process parameters, particularly moulding temperatures, on the 3D-formability of bioplastics during thermoforming. A numerical/visual comparison was conducted between thermoformed tray packages and reference packages made of petrochemical polymers focusing primarily on product geometry and stiffness. Three bioplastic materials were selected based on their availability and suitability for the process: Polylactic Acid (PLA) and Cellulose Acetate Propionate (CAP). The sample materials were formed to specimen trays using a custom-designed sheet-forming chamber on a commercial Form-Fill-Seal (FFS) thermoforming line. Material changes necessitated separate optimizations of the process parameters for each material. It was found that the material properties of bioplastics set certain limits to the formed geometric shapes, but these limits can be addressed during the packaging design phase, making bioplastics a viable material for environmentally friendly yet economically feasible packages.