Facilitating mechanical strength in water-based polybenzoxazine aerogels via chemical cross-linking

Polybenzoxazine (PBz) aerogels have garnered significant attention as advanced thermal insulation materials, primarily attributed to their superior thermal stability and lightweight nature. However, their mechanical properties need further improvement for high-load scenarios. Furthermore, the reliance on toxic solvents, cumbersome preparation processes, and high costs has significantly impeded the advancement of PBz aerogels. Herein, we present a novel methodology for fabricating polybenzoxazine-based (PBz/KH562) hybrid aerogels with enhanced mechanical properties. Notably, the integration of 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane (KH562) through a sustainable process yields aerogels exhibiting a low density (0.39 g·cm⁻³), low thermal conductivity (0.0556 W·m⁻¹·K⁻¹), and outstanding fire resistance. The optimized PBz/KH562 hybrid aerogels demonstrate a compressive strength of 8.45 MPa at 10% strain and 5.11 MPa at 5% strain, representing remarkable increases of 451.87% and 477.57% compared to those of pristine PBz aerogels, respectively. Remarkably, the compression modulus is up to 101.15 MPa. This research establishes an advanced synthesis method that incorporates a novel dual-crosslinked architecture, facilitating the creation of high-performance insulating materials. • The PBz/KH562 aerogel was prepared by a toxic-solvent-free aqueous synthesis. • The PBz/KH562 hybrid aerogel exhibits a high compressive modulus up to 101.15 MPa. • KH562 addition resulted in a 477.57% strength gain to 5.11 MPa at 5% strain. • PBz/KH562 aerogel self-extinguishes in 1.8 s, showing outstanding flame retardancy. • Ambient drying of PBz/KH562 aerogels simplified the process and cut costs.