Comparative study of processing-cellular morphology-property relationships of PU and PBDMS-PU foams

Abstract

This study investigates the morphology and mechanical properties of polyurethane (PU) foams with varying flexibility levels compared to polyborodimethylsiloxane-based polyurethane (PBDMS-PU) foam (D3O) under low strain rates. While PU foams are widely used for impact protection and cushioning, their performance varies based on processing parameters and material composition. However, a systematic comparison of their energy dissipation and recovery under cyclic loading is lacking. This study addresses this gap by analyzing the processing-structure-property relationships of these materials to determine whether PU foams can replicate D3O’s mechanical behavior. PU foams were synthesized using polyether polyols, acrylic polyols, and 4,4′-diphenylmethane diisocyanate (pMDI), with water as the blowing agent. Characterization techniques, including SEM, TGA, and cyclic compression tests, were utilized. The results show that semi-flexible PU foams exhibit pore structures and densities similar to D3O, while rigid PU foams demonstrate 62% higher density and 35–40% greater compressive strength, leading to superior mechanical performance. D3O maintains >95% recovery after 10 compression cycles and exhibits stable energy dissipation, with only a 5–10% drop in peak stress after repeated loading, comparable to semi-flexible PU foams. However, D3O has lower thermal stability (T₃₀ = 357°C) than PU foams (T₃₀ = 366–370°C), despite enhanced high-temperature resistance (T₅₀ > 390°C). This study highlights the tunability of PU foams for energy absorption applications, providing insights for optimizing their mechanical and thermal properties.