Synthesis of a boron modified phenolic resin

Abstract

Phenolic resin has long been used as matrix for composites mainly because of its flame retardant behavior and high char yield after pyrolysis, which results in a self supporting structure. The addition of ceramic powders, such as SiC and B 4 C, as fillers to the phenolic resin, results in better thermo-oxidative stability, but as drawbacks, it has poor homogeneity, adhesion and processing difficulties during molding of the composites. The addition of single elements, such as boron, silicon and phosphorus in the main backbone of the thermo-set resin is a new strategy to obtain special high performance resins, which results in higher mechanical properties, avoiding the drawbacks of simply adding fillers, which results in enhanced thermo-oxidative stability compared to conventional phenol-formaldehyde resins. Therefore, the product can have several applications, including the use as ablative thermal protection for thermo-structural composites. This work describes the preparation of a boron-modified phenolic resin (BPR) using salicyl alcohol and boric acid. The reaction was performed in refluxing toluene for a period of four hours, which produced a very high viscosity amber resin in 90% yield.The final structure of the compound, the boric acid double, substituted at the hydroxyl group of the aromatic ring, was determined with the help of the Infrared Spectroscopy, 1 H-NMR, TGA-DSC and boron elemental analysis. The absorption band of the group B-O at 1349 cm-1 can be visualized at the FT-IR spectrum. 1 H-NMR spectra showed peaks at 4.97-5.04 ppm and 3.60-3.90 ppm assigned to belong to CH 2 OH groups from the alcohol. The elemental analysis was also performed for boron determination.The product has also been tested in carbon and silicon fibers composite for the use in thermal structure. The results of the tests showed composites with superior mechanical properties when compared with the conventional phenolic resin.

Effect of boron carbide nanoparticles on the thermal stability of carbon/phenolic composites

“…Another possible approach to improve the thermal properties of phenolics is related to the use of boron containing precursors; typically the modification is carried out by reacting phenol, formaldehyde, and boric acid using sodium hydroxide as catalyst . The higher resistance was due to the presence of BO borate linkages.…”

Electrical Behavior of Carbon Fiber/Phenolic Composite during Pyrolysis

“…Up to ~350°C, there are no significant molecular size changes, only small molecular bridge transformations occur. Beyond 350°C, the cracking phase occurs, related to molecular degradation, reduced molecular mass [33][34][35] . Elements such as H 2 O, CO, CO 2 , H 2 are released as volatiles.…”

Improving the Mechanical Properties of Fiber Metal Laminate Composite Used in Aircraft Wing

“…The properties and chemical composition of Aluminum sheets can be showed in Tables 4& 5 respectively. Resole resin was produced by reaction between formaldehyde and phenol under base PH conditions with excess formaldehyde that led to the molar formaldehyde to phenol ratio greater than one (> 1) [14]. Resole resin is produced locally from That Al-Sawary Company /Baghdad/Al-taji in Iraq.…”