Effect of Boron Modification on Characteristics of Phenolic Resin and Its Char

ABSTRACT Resole type Phenol‐formaldehyde resins are known for their thermal stability and char yield. The thermal and ablative performance of phenolic resins can be further improved by incorporating inorganic elements like boron to the phenolic resin structure. These modifications can also affect the structure and properties of char which is formed during ablation. This paper aims at comparing the properties of phenolic resin and its char, with and without boron modification. Differential scanning calorimeter (DSC), Dynamic mechanical analysis (DMA), Rheometer was used to study the cure behavior of the liquid resins. Using Thermogravimetric analysis (TGA), the change in thermal stability and char yield with change in cure temperature was studied for the modified resin. TGA revealed a better thermal stability, with increase in temperature of maximum degradation rate by 62°C and increase in char yield from 55% to 70% in case of boron modified phenolic resins. The rheometer data shows that phenolic resin gelation takes place after 140°C, whereas for modified resins, gelation takes place after 200°C indicating a higher reaction temperature for the modified resin. The char obtained by pyrolysis of the resins at 800°C was characterized using FTIR, X‐Ray photoelectron spectroscopy (XPS) and X‐Ray diffraction (XRD). From thermal stability and char yield studies, it can be concluded that boron modified resin system is superior to the phenolic resin making it a potential candidate for high temperature and ablative applications.