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Thermoforming of fibre‐based materials faces challenges due to their restrictive three‐dimensional formability and lack of compatibility between material properties and traditional thermoforming methods. Treatment techniques present an intriguing area of research to address the gap between material characteristics and process requirements. Therefore, this study examined the influence of inline steam treatment on the thermoforming of plastic‐coated fibre‐based materials with different product geometries. Three plastic‐coated paperboards were subjected to thermoforming, with and without steaming, and their thermoformability was assessed based on the maximum depth and draft angle of the samples. Following 7 s of steaming, the materials exhibited a moisture content 2–4 percentage points higher than that of the original setup, yielding a greater curling rate in the produced samples across different geometries. The curling rate was influenced by the tensile stiffness of the materials and was correlated with the size of the flat‐edge area in the studied geometries. Furthermore, findings revealed varying rates at which steaming affected different geometries. Steaming substantially enhanced the achieved depth for geometries where the material was incapable of reaching the mould without moisturization, particularly observed for smaller geometrical shapes. This improvement was linked to steaming, which enhanced pliability, facilitated material penetration, and increased the final depth. However, in geometries where the material could reach the mould without moisturization, steaming expanded the contact area but could also result in a greater spring‐back rate and reduced depth, potentially owing to the loss of elastic modulus by moisturization. Nevertheless, the rate of spring‐back did not consistently increase with steaming and could be influenced by various material‐related factors, including the properties, composition, preparation methods, and postforming drying. Despite depth changes, steaming consistently improved the obtained draft angles, indicating that the materials were drawn more efficiently to the sidewalls across all instances studied. Thus, this study underscored the importance of choosing appropriate materials and moulds for hydrothermal moisturization treatments in the thermoforming process. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]