Facile Preparation of Lightweight and Robust Polybenzoxazine Foams

Abstract

Lightweight and robust polybenzoxazine foams were prepared using a simple sol–gel method based on a commercially available benzoxazine monomer, BA-a, with hexamethylenediamine as a curing agent and methanol/chloroform as the solvent. By varying the initial concentrations of organic solutions, polybenzoxazine foams with densities of 0.2815 g/cm3 (F-20), 0.4798 g/cm3 (F-30), and 0.6731 g/cm3 (F-40) were prepared. Scanning electron microscopy (SEM) images revealed that all foams possessed open-cell structures, and the morphology of the pore walls can be readily tailored by initial concentrations. As a consequence of the porous structure, the polybenzoxazine foams showed a low dielectric constant (1.47 at 1 MHz for F-20), low dielectric loss (0.003 at 1 MHz for F-20), low thermal conductivity (0.0604 W/(m K) for F-20), and low coefficient of linear expansion value (55.1 ppm/°C for F-20). Moreover, foam F-40 showed a favorable T g of 191.8 °C, char yield of 46.1%, and compressive strength of 71.74 MPa. The outstanding comprehensive performances make the polybenzoxazine foams prepared using this methodology good candidates as lightweight, robust, and thermally stable matrices for many functional applications.

Facile preparation and properties of polybenzoxazine/graphene porous nanocomposites for electromagnetic wave absorption

“…Xiao et al [ 24 ] obtained polybenzoxazine aerogels with good thermal insulation by oxalic acid‐catalyzed pre‐polymerization at a low temperature followed by subsequent aging and curing at a high temperature. Zhang et al [ 25 ] prepared polybenzoxazine aerogels by a sol–gel method and obtained the foams after further thermal curing. The properties of the foams can be adjusted by changing the solid content of the solution.…”

Significantly Enhanced Porosity of Silicone Rubber Nanocomposite Foams via Cross-Linking Structure Regulation and Heterogeneous Nucleation by CNTs for Promising Ultralow-k Dielectrics

“…However, the nanoporous filler POSS has a high cost, and the introduction of pores is very limited. Zhang et al 22 used the sol−gel method to fabricate polybenzoxazine foams with different densities by varying the initial concentrations of organic solutions. As the density of the foam decreased from 0.6731 to 0.2815 g/cm 3 , its dielectric constant reduced from 2.81 to 1.53.…”

Facile Preparation and Improved Electrochemical Performance of Oxygen‐Enriched Porous Carbon Materials Based on Diacetal‐Containing Polybenzoxazine

“…For example, Feng et al [39] used melamine as a sacrificial material to successfully obtain a sheetstacked porous carbon material with different pore size distribution during the carbonization. In addition, we have previously used melamine to react with benzoxazines to prepare foams, [40,41] which can be used as an ideal precursor for porous carbon materials.…”