Enhancing Compression Performance and Morphology of Flexible Polyurethane Foam via Al2O3 Nanoparticle Reinforcement

Abstract

Flexible polyurethane foam is widely used for cushioning and structural applications. However, it always faces limitations in mechanical strength and cell stability. The incorporation of inorganic nanoparticles such as aluminum oxide (Al₂O₃) offers a good alternative to overcome these drawbacks by enhancing foam morphology and mechanical resilience. The present work aims to explore the influence of Al₂O₃ nanoparticle reinforcement on the compression behavior and cellular morphology of synthesized flexible PU foam. The novelty of this work is to show that low Al₂O₃ loadings can refine the cellular architecture and improve the compressive response by achieving a balance of flexibility and strength that is not typically attainable with conventional fillers. PU foams were synthesized via a one-shot method with 0, 0.2, and 0.4 g Al₂O₃ nanoparticles incorporated as fillers. Scanning Electron Microscopy (SEM) revealed progressive cell refinement with increasing nanoparticle content, where pore size decreased from 1.65–1.81 mm in the neat PU, 1.45–1.46 mm with 0.2 g Al₂O₃ and 824 µm at 0.4 g filler loading. Compression testing confirmed that this morphological refinement improved strength, as Al₂O₃ acted as nucleating agents, by limiting bubble growth allowing more uniform cellular structure. Therefore, the foam with 0.4 g Al₂O₃ delivered the best balance of mechanical strength and flexibility. In general, this study demonstrates that controlled incorporation of Al₂O₃ nanoparticles is an efficient strategy to control the microstructure and mechanical properties of flexible PU foams.