This study proposes producing sandwich composites that have functionalities in addition to good mechanical properties. Flexible polyurethane (FPU) foam is used as the core, whereas nonwoven fabrics are used as the top and bottom panels. The functionalities, including flame‐retardant (FR) efficacy, acoustic absorption, and electromagnetic shielding effectiveness (EMSE), help in expanding the application fields. In this study, FR agent is added to FPU foam to form the core, while the low‐melting point polyethylene terephthalate (LPET) nonwoven fabric with/without carbon fiber (CF) fabric is used as panels. One‐step molding and hot pressing are used to make these materials into LPET/FPU and CF‐LPET/FPU sandwich composites. The cell structure of the FPU foam is examined, after which the limit oxygen index (LOI), the compression modulus, and heat insulation efficacy of LPET/FPU sandwich composites are examined, thereby examine the influence of FR agent. The test results show that the mechanical properties of sandwich composites are dependent on the amount of FR agent. Using 50 wt %, FR agent provides LPET/FPU sandwich composites with an optimal LOI of 28. In addition, the combination of CF fabric further provides CF‐LPET/FPU composite sandwich with the maximum acoustic absorption coefficient of 0.90376 and an optimal EMSE of 50 dB. The proposed sandwich composites have functionalities of FR efficacy, acoustic absorption, heat insulation, and EMSE and thus are qualified for protective partitions used in karaoke and kindergartens. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46871.

The incorporation of particles with soft polyurethane (PU) foam aims to mechanically strengthen the PU foam as PU foam falls short of the mechanical expectation of academia and industries. In this study, the expanded polystyrene (EPS) particles are added to soft polyurethane foam, and composite foam with higher mechanical properties is successfully prepared by one‐step foaming process. The results show that under optimal conditions that is, EPS particle size of 0.5 mm and content of 2.5 wt% (EPS‐0.5‐2.5%), the synthesized foam has the smallest bubble pore diameter of 80 μm and has a stress of 0.284 MPa at 75% strain, which is much higher than that of blank polyurethane foam. As a result of a rise in the quantity of EPS particles, the composite PU foam shows a lower dependency on the strain rate. After the multiple cyclic compression test, PU foam exhibits a descending trend on the stress in the deformation plateau region. Besides, the low‐velocity impact test results indicate that the peak contact force of EPS‐0.5‐2.5% is lower than that of the control group by 632 N.