Study Of Titanium-modified Phenolic Resins

Phenolic formaldehyde resins(PF) are widely used in the thermal protection of the spacecraft for their excellent heat resistance and good process performance. With the development of the spacecraft industry, extensive research has been enhanced to improve the heat resistance, thermal stability of PF. It is reported that the addition of inorganic compounds are used to modify the phenolic resins to improve PF's high temperature resistance performance and flame retardancy. The addition of heavy metals is less researched, while the heavy metal modification of PF can improve PF's high temperature resistance performance effectively. In this paper, titanium element is introduced into the structure of PF by chemical modification.A new type of titanium-modified phenol-formaldehyde resin (Ti-PF) was prepared by the compounds such as phenol, paraformaldehyde and tetraisopropyl titanate. The char yield of the PF has been increased 11% by the addition of titanium compounds.The titanium content, phenol-formaldehyde ratio, esterification time, condensation temperature and condensation time are the main five factors that affected the char yield of titanium modified phenolic resin. The best synthesis condition is obtained by the orthogonal experiment method with the five factors and four levels. The single-factor experiment was used to obtain the optimum conditions to synthesis titanium modified phenolic resin. Experimental results show that titanium content is the biggest factor affecting the char yieled, followed by the esterification time and then the condensation time. The best level of titanium content is 1%, the best ratio of phenol formaldehyde is 1.8:1, the best esterification time is 20 minutes, the best reaction temperature is 80℃, the best reaction time is one hour.FT-IR was adopted to characterize the molecular structure of the modified resin and unmodified resin. The thermal degradation behavior of the cured Ti-PF was studied by thermal gravimetric (TG) method. In addition, the curing behavior and curing kinetic characteristics were studied by differential scanning calorimetry (DSC). X-ray diffraction was used to analyze the structure of the white powder which was the residual of the titanium phenolic resin under high temperature in the air.