High sound insulation property of prepared polypropylene/polyolefin elastomer blends by combining pressure-induced-flow processing and supercritical CO2 foaming

Light weight, high sound insulation property polymers have vast potential application in aviation, auto industry and the military application. Pressure induced flow (PIF) process form multi-layer-oriented structure in polymer matrix, and supercritical CO2 foaming (ScCO2) introduce gas into the matrix and increase the impedance mismatch between the phase, both of them enhance the polymer sound insulation property. In this paper, the sound insulation property of polypropylene (PP)/polyolefin elastomer (POE) blended composites prepared by the PIF process and the ScCO2 foaming were measured using the impedance tube. The sound insulation property is up to 103.56 dB in the frequency band of 1000–6000 Hz for 5 mm PIF PP/POE foam material, which it is 67.15 dB higher than PP/POE foam. By employing the multi-scale ffinite element analysis (FEA) modeling method, one two-phase FEA model of the monolith of 0.1 mm size and another 29 mm diameter bulk sample were developed based on SEM image of PIF PP/POE foamed materials at different scales. The monolith FEA model provided the effective material property for bulk sample. The finite element calculation results were consistent with the experimental result, verified the validity of the FEA modelling approach. The FEA simulation results reveal that the multi-layer-oriented structure of PIF material introduce the multi-layer impedance mismatch inside each monolith, and incident sound wave is reflected by those impedance mismatch, and this mechanism produce the high sound insulation property of PIF PP/POE foam materials.