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Polybenzoxazine aerogels have gained much attention as a new type of polymeric aerogels in the field of flame resistant materials. Herein, a unique method for the preparation of fiber-reinforced PBa composite aerogels has been reported using polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC) as dispersion carriers through freeze-drying for surface modified basalt fibers (Z@BF). Bisphenol-A type benzoxazine (Ba) monomer was used as the matrix, which infiltrated into the carrier for dispersed fibers to obtain a PBa composite gel by sol-gel method. Solvent exchange and ambient drying techniques were used to obtain the final composite aerogel samples. Z@BF formed a double-network structure with the aerogel matrix, which resulted in 55.43% increase in compressive strength, a low volumetric shrinkage (27.46%), and density (0.19–0.21 g cm 3) of the prepared aerogel. The addition of Z@BF increased the residual carbon content (59.6% at 800 °C) in the aerogel, while reducing the total heat release rate by 36.9% and the peak heat release rate by 60.61%. Besides, the aerogels possessed excellent self-extinguishing property, and the self-extinguishing time was only 1.31 s after flame burning at 1200 ℃ for 10 s. The composite aerogels obtained by this combination of atmospheric pressure drying and freeze-drying techniques not only possessed high mechanical strength and excellent flame retardant properties, but also provided a new idea for the preparation of fiber-reinforced PBa aerogels. This would further expand the potential use of PBa aerogels in flame retardant materials. [Display omitted] • A polybenzoxazine composite aerogels system capable of effectively dispersing fibers with flame retardant properties is designed. • Basalt fibers enhanced mechanical and flame retardant properties of polybenzoxazine composite aerogels are realized. • The polybenzoxazine composite aerogels have excellent self-extinguishing properties and low combustion shrinkage upon flame ignition (1200°C). • The polybenzoxazine composite aerogels have a low peak heat release rate of 115.5 kW/m2. [ABSTRACT FROM AUTHOR]

Polybenzoxazine/Melamine (PBa/MS) double network aerogels were prepared using melamine foam (MS) as the backbone and bisphenol A-type benzoxazine (Ba) as the maxtrix. The effect of Ba concentration in the sol-gel on the performance of the double network aerogel was investigated. During the combustion, the PBa/MS composite aerogel exhibited self-extinguishing performance. Compared with PBa-18%, the contact angle of PBa-18%/MS composite aerogel was 18° higher, and the heat release peak (PHRR) and total smoke production (TSP) of the composite aerogel decreased by 7% and 39%, respectively. These values indicate that MS can significantly reduce the release of heat and smoke from the PBa aerogel, thus improving its flame retardancy. In addition, the composite aerogel formed a denser and more complete carbon layer during combustion, which blocks both heat and mass transfer. Thus, the resulting PBa/MS dual-network composite aerogels obtained in the current work are expected to meet the demands for flame-retardant, hydrophobic thermal insulation materials in many fields. [Display omitted] • Benzoxazine/melamine composite aerogel has a double network structure. • Aerogels was prepared through drying at normal temperature and pressure. • Aerogel owned the properties of flame retardancy, smoke suppression, resilience, heat insulation and hydrophobic properties. • The composite aerogel has good thermal insulation at 200 ℃. [ABSTRACT FROM AUTHOR]