Foaming strategy-governed structure-property relationships in microcellular polyurethane elastomers

Microcellular polyurethane elastomers (MPUE_s) are widely used in vibration and noise control, yet the influence of foaming strategy on their structure and properties remains poorly understood. This work provides a systematic comparison between high-pressure (HP) and low-pressure (LP) foaming processes, evaluating their effects on the microstructural development and functional properties of MPUEs. Through a combination of analytical techniques, including SEM, FTIR, AFM, and DMA, we observed that HP foaming markedly improves microphase separation, reflected by a 10% rise in the hydrogen bonding index. This method also yielded a more uniform cell structure, with a cell density reaching 4.1×10⁶ cells/cm³, which is ten times higher than the result from LP foaming. These structural advantages led to a 28% improvement in Young's modulus and lower hysteresis loss, highlighting the importance of well-formed hard-segment regions and refined cell morphology. Furthermore, HP-foamed MPUEs showed better vibration isolation performance, with lower transmissibility and a reduced resonance frequency. We attribute these gains to the combined improvements in the polymer matrix and foam architecture, which collectively enhance mechanical and dynamic performance. Our study confirms that HP foaming is a highly efficient processing technique for producing high-performance MPUEs with customized properties, showing great potential for advanced industrial damping applications.