One‐Step Preparation of Lightweight Pulp Composite Foams with Synergistic Flame Retardant and Multiscale Insulation Structures

Abstract Flame retardant properties are critical for the use of foams in packaging and transportation applications. However, the process of preparing conventional flame retardant foams is complex and adversely affects their thermal insulation and mechanicl properties. Here, a convenient and scalable synergistic strategy is reported to prepare synergistic flame‐retardant, heat‐insulating cellulose‐based foams with stabilized laminar structures through a one‐step physical blending of ammonium polyphosphate (APP) and vacuum glass microspheres (HGMs), which exhibit lightweight (72.18 mg cm −3 ), enhanced flame retardant properties (pHHR reduced from 109.6 to 67.3 kW m −2 ), excellent barrier effect (E Barrier increased by 45.82%), excellent thermal conductivity (with a thermal conductivity of 59.9 mW mK −1 ) and good mechanical properties (stress of 57.53 kPa at 80% strain). In addition, the foam can be recycled by easy methods. Therefore, the present work provides a feasible approach for flame retardant and heat‐insulating bio‐based foams and has a wide range of applications in packaging and construction materials.