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<p>The formation of polyurethane rigid (PUR) foams is a complex process involving multiple interrelated chemical and physical mechanisms. One critical parameter for thermal insulation applications is the pore size<b>,</b> which has been shown to be reduced by adding fluorocarbons (FCs) to the foam formulation. While recent studies confirm this phenomenon, the underlying physico-chemical mechanisms remain unclear. In this study, we employ cryogenic scanning electron microscopy (Cryo-SEM) to investigate the evolution of nascent PUR foams and the role of FCs in shaping their morphology. Two PUR foam systems—a simplified “scientific system” and an industrially relevant “technical system”—were analysed under both laboratory and pilot-scale conditions. Our results confirm a recently formulated hypothesis that FCs impact foam structure primarily by increasing the number of entrained gas bubbles which act as heterogeneous nucleation sites. We also put in evidence the formation of interfacial FC films around the bubbles, which may affect foam stabilisation and growth dynamics. Additionally, we observe an unexpected stagnation in bubble growth in the presence of FCs, highlighting the need for further investigations. This study provides new insights into the role of FCs in pore size control and may contribute to finding alternative&#xa0;additives for PUR foam formulations with enhanced thermal insulation performance<b>.</b></p> Graphical Abstract <p></p>

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Role of fluorocarbons in PUR foams: a cryo-SEM study

  • 期刊论文

  • 发表日期：

    2025年8月20日

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  • Martin Hamann,
  • Alain Carvalho,
  • Marc Schmutz,
  • Luca Fiorucci,
  • Daniel Telkemeyer,
  • Markus Schütte,
  • Wiebke Drenckhan-Andreatta

摘要

The formation of polyurethane rigid (PUR) foams is a complex process involving multiple interrelated chemical and physical mechanisms. One critical parameter for thermal insulation applications is the pore size, which has been shown to be reduced by adding fluorocarbons (FCs) to the foam formulation. While recent studies confirm this phenomenon, the underlying physico-chemical mechanisms remain unclear. In this study, we employ cryogenic scanning electron microscopy (Cryo-SEM) to investigate the evolution of nascent PUR foams and the role of FCs in shaping their morphology. Two PUR foam systems—a simplified “scientific system” and an industrially relevant “technical system”—were analysed under both laboratory and pilot-scale conditions. Our results confirm a recently formulated hypothesis that FCs impact foam structure primarily by increasing the number of entrained gas bubbles which act as heterogeneous nucleation sites. We also put in evidence the formation of interfacial FC films around the bubbles, which may affect foam stabilisation and growth dynamics. Additionally, we observe an unexpected stagnation in bubble growth in the presence of FCs, highlighting the need for further investigations. This study provides new insights into the role of FCs in pore size control and may contribute to finding alternative additives for PUR foam formulations with enhanced thermal insulation performance.

Graphical Abstract