Fabrication of Dense Crosslinked Network in Polybenzoxazine Aerogels via Melamine for High Compressive Strength

Polybenzoxazine (PBz) aerogels fabricated via a water–ethanol mixed green system are attractive for thermal insulation but are limited by inherent brittleness and the environmental burden of their conventional fabrication. To address this, we developed a high‐strength hybrid aerogel through a water‐ethanol mixed green strategy, employing melamine (Ma) as a chemical crosslinker. The reaction between Ma and the PBz precursor constructs a dense, chemically bonded network, which yields a remarkable compressive strength of 6.80 MPa at 10% strain—approximately 377% that of the PBz aerogel. This marked mechanical enhancement is achieved without compromising its overall performance, featuring a low density of 0.42 g cm −3 , a thermal conductivity of only 0.059 W m −1 K −1 , and improved flame resistance. This work successfully overcomes the traditional compromise between environmentally friendly processing and high performance, offering a feasible and scalable route to produce strong, lightweight, and fire‐resistant PBz‐based aerogels for advanced thermal insulation applications.