Preparation and characterization of polybenzoxazine foam with flame retardancy

Polybenzoxazine foam was successfully prepared using phenolic resin as modifier and catalyst. The structural properties, curing behavior, thermal stability, cellular structure, mechanical properties and flame retardancy properties of the foam were characterized by Fourier transform infrared (FTIR) spectrometry, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), compression tests, limiting oxygen index (LOI) tests and cone calorimetry test, respectively. The experimental results indicated that both phenolic resin and imidazole catalyzed the curing process of benzoxazine and that the curing temperature decreased obviously. The polybenzoxazine foam loaded with different contents of phenolic resin showed an isotropic cellular structure with relative densities ranging from 116 to 185 kg/m(3), and the compressive strength and compressive modulus could reach as high as 0.512 and 7.21 MPa, respectively. In addition, the cone calorimeter test results showed that the average heat release rate (av-HRR), total heat release (THR) and total smoke production (TSP) of PBZ-7.5 reduced, which indicated that the polybenzoxazine has satisfactory flame retardancy with the addition of phenolic resin.