Pyrolysis Behavior of Boron-Containing Phenol-Formaldehyde Resin (BPFR) Modified by B_2O_3

摘要

In this study, pure boron-containing phenol-formaldehyde resin (BPFR) and boron oxide (B_2O_3) modified BPFR have been pyrolyzed at elevated temperatures in air and their thermal decomposition behavior is mainly explored. The structural evolution and chemical composition change during pyrolysis are characterized by thermal gravity (TG), Fourier-transform infrared (FT-1R) spectroscopy, X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). It is shown that the mass residues of pure BPFR are 27.1 and 8.7 wt.% after being pyrolyzed at 600 and 1000 °C for 2 h, respectively. In comparison with the pure BPFR, the mass residue of _2O_3 modified BPFR is obviously higher, with the values of 72.9 and 39.7 wt.% at 600 °C and 1000 °C, respectively. The results of FT-IR prove the degradation and failure of the resin matrix are mainly resulted from the fracture of methylene and the release of small molecules. The XRD characterization shows the residues are amorphous carbon and B2O3. FE-SEM exhibits the melting _2O_3 layer formed on the surface of the samples which could prevent oxygen from diffusing into composites during oxidation to some extent.