The effect of the polymer film selection on the stiffness and applicability of the thermoformed tray package

Abstract

Bioplastics are materials processed from renewable natural resources and equipped with competitive properties, which aim to replace traditional oil-based plastics in sustainable food packaging. Since bioplastics are most often targeted to replace current alternatives in the same production processes and machines, their functionality in processing and above all in end use is vital for the change to take place smoothly. The aim of this study was to determine how process parameters, especially forming depth and moulding temperatures, affect the 3D-formability of plastic alternatives in thermoforming process. A bioplastic sample, Cellulose Acetate Propionate (CAP), selected according to the requirements of the end-use application and oil-based competitor, APET/EVOH/PE multilayer plastic, as a reference were tested in forming experiments. Sample materials were tested using an industrial grade Form-Fill-Seal (FFS) thermoforming line equipped with a custom-designed sheet-forming chamber. The final products, i.e. thermoformed tray packages, were evaluated by measuring their torsional stiffness and compression strength. Based on the results, the more than half thinner Bioplastic sample was found to have notably sufficient properties for the thermoforming process and the manufacture of the test package. From the point of view of processability and the functionality of the final product, both samples were found to be applicable, and the change of material type between them does not cause measures greater than fine-tuning of the thermoforming process.