Innovation in rotational foam molding: Water as performance enhancer in blowing agent-free foam molding

Werner J, Oktaee A, Wormser M, Nürnberg HP, Drummer D (2026)

Publication Type: Journal article

Publication year: 2026

Journal

Journal of Cellular Plastics SAGE Publications (UK and US)

DOI: 10.1177/0021955X261459005

Abstract

Sustainability drives the development of new or optimised methods in plastics technology, one of which is the vacuum assisted rotational foam molding process, as it refrains from the use of chemical blowing agents. Process inherent air inclusions in the polymer melt thereby act as nuclei for cell growth induced by means of an applied vacuum. This manuscript addresses the influence of the moisture content in the employed powders and characterizes its impact on the foaming level. The findings reveal that the formation of air inclusions, beyond those generated during sintering processes in melting is significantly intensified by the evaporation of water molecules during polymer heating. The increased number of initially present gas inclusions allows to obtain higher foaming degrees. Two types of thermoplastic polyurethane (TPU) materials with distinct hardness levels were examined closely, revealing a positive correlation between elevated shore hardness and a shift in the water release to higher temperatures. In materials with lower shore hardness, water release occurs at lower temperatures, before the polymer melt forms, and thus does not contribute significantly to foaming. The effect is believed to be due to a stronger molecular binding of water through hydrogen bonding in the material with a higher hard segment content. Notably, the contribution to foam expansion is more pronounced at higher hardness gradients. This work provides an overview of the possibilities to influence the foaming degree through the initial moisture content in the materials used, as well as the importance of proper material conditioning for better property prediction.

Authors with CRIS profile

Jannik Werner Lehrstuhl für Kunststofftechnik (LKT) Aryan Oktaee Lehrstuhl für Kunststofftechnik (LKT) Dietmar Drummer Lehrstuhl für Kunststofftechnik (LKT)

Involved external institutions

Adidas AG DE Germany (DE)

How to cite

APA:

Werner, J., Oktaee, A., Wormser, M., Nürnberg, H.P., & Drummer, D. (2026). Innovation in rotational foam molding: Water as performance enhancer in blowing agent-free foam molding. Journal of Cellular Plastics. https://doi.org/10.1177/0021955X261459005

MLA:

Werner, Jannik, et al. "Innovation in rotational foam molding: Water as performance enhancer in blowing agent-free foam molding." Journal of Cellular Plastics (2026).

BibTeX: Download