The effect of titanium incorporation on the thermal stability of phenol-formaldehyde resin and its carbonization microstructure

A new titanium modified phenolic resin (Ti-PF) was prepared by using tetraisopropyl titanate, phenol and formaldehyde with mild and friend reaction condition. The structure of the modified resin was demonstrated by means of FT-IR spectra. The titanium modified resin is soluble only in a few solvents such as DMF, DMAc, DMSO, but exhibits poor solubility in most universal solvents. The thermal degradation behavior of the Ti-PF was studied by thermal gravimetric (TG) method. Compared with the unmodified resin (PF), the temperature at the maximum decomposing rate of the Ti-PF increases by 43 °C and its charring yield enhances by 11 percent. The carbonized products of PF (C-PF) and Ti-PF (C-Ti-PF) were further investigated by X-ray diffraction and Roman spectroscopy, respectively. The analysis indicates that the incorporation of titanium into carbon lattice results in an increase of crystallite height and decrease of interlayer spacing. Titanium modified PF becomes much more ordered with a d002 of 0.3572 nm as compared to that of 3.7811 nm for C-PF. And the crystal size of C-Ti-PF increases to 4.37 nm, 2.13 nm larger than that of C-PF. In addition, the ID/IG value of C-Ti-PF decreases from 2.85 (C-PF) to 2.62. The results prove that the incorporation of titanium exhibited obvious effects on improving thermal stability of the phenolic resin and on promoting its graphite crystallite.