Effects of thermoforming operation and tooling on the thermoformability of plastic‐coated fibre‐based materials

Abstract

Advances in the three‐dimensional (3D) forming of fibre‐based materials require the formulation of more formable materials and the development of process lines, machinery, and tools. Using a thermoforming process to convert fibre‐based materials into 3D forms is an emerging area of research which requires further investigation into the practicality of the process line and tooling in forming such materials. Accordingly, this study evaluated the impact of the thermoforming process operation and tooling on the thermoformability of plastic‐coated paperboards. The main objective was to provide design recommendations for the future development of thermoforming lines, followed by guidelines for tooling design to improve the performance of materials utilising the currently available machinery. This study examined the thermoforming behaviour of two different plastic‐coated paperboards in vacuum and pressure thermoforming by investigating their maximum acquired depth, shape accuracy, and damage mechanisms. The research findings, based on the depth and linear elongation achieved, indicate that the inferior performance of plastic‐coated paperboards in thermoforming cannot be wholly attributed to restrictions in the three‐dimensional formability of materials; the inability of the current process lines to utilise the maximum potential of materials can also lead to their inferior performance. Notably, the method of pressure supply and cooling of materials requires adjustment of these materials. From a tooling perspective, owing to the spring‐back effects, the enlargement of the mould dimensions should be considered during the design stage. Additionally, based on potential opportunities with the current unmodified machinery and materials, products in the size of standard food trays have a higher likelihood of being optimised with tooling design than smaller sized shapes, which still require additional developments in materials. Moreover, designing moulds without draft angles can reduce the risk of rupture owing to the prevention of localised stress formation in materials.

Thermoformability study of wood flour–HDPE composites with variations in wood content under vacuum forming

“…The slight variation in the values obtained could be related to both the measurement error and nonuniformity of the surface flatness. In a previous investigation, it was observed that spring-back occurred during the thermoforming process of multilayer fiber-based composites [ 45 ]. However, the attainment of an identical depth as the mould for these mixed structure WPCs could indicate the absence of significant spring-back for this particular geometry and the employed process.…”