Investigation of an optimized hot press process design for manufacturing structural polyethersulfone foams

Abstract

Semi-finished thermoplastic foam panels can be transformed into structural foams—a sandwich-like structure with high-density skins—through thermoforming. This transformation enables the production of mono material sandwich panels, which allow a significant increase in bending properties without increasing the part weight. This study describes the effect of process parameters on skin formation in thermoplastic structural foams manufactured in a two-step isochoric and isothermal hot press process. Process data recorded during foam manufacturing was analyzed and compared to foam behavior in quasi-static isothermal compression tests performed at different levels of temperature and crosshead speeds. The effect of skin-core structure on bending properties is compared to theoretical models from the established literature. It was found that a rule of linear mixture that considers the relative skin thickness allows adequate prediction of both bending modulus and strength. Preferable process design—especially combinations of tool temperature and maximum compaction speed—is described based on the comparison of measured and predicted performance.

Graphical Abstract

Keywords:

• Thermoplastic foams
• polyethersulfone
• amorphous polymer
• compressive properties
• structural foam
• microsandwich
• divinycell F
• closed cell foams

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability

The data that support the findings of this study are available from the corresponding author, upon reasonable request.

Additional information

Funding

This study has been conducted in the frame of the research project ‘Sophia Smart processes and optimized designs for high production cadences’ funded by the Federal Ministry of Economic Affairs and Energy (BMWi) on the basis of a decision by the German Bundestag (Funding Reference 20X1715D).