Boron-modified phenolic resins for high performance applications

A boron-modified phenolic resin (BPR) that flows at usable processing temperatures was prepared from the solvent-less reaction of triphenyl borate (TPB) and paraformaldehyde (PF). The reaction of TPB and PF was performed at three different resinifying temperatures, 130, 120 and 90 °C. The BPR produced at 90 °C melted upon reheating, which indicated promising processing applications for this resin. 1H and 13C NMR spectra of resins from the three resinifying temperatures had the same pattern of absorptions. Substitution of methylol groups occurred at the ortho and para positions of the ester phenyl rings (4.86–4.75 ppm). Aromatic, methylene and ether linkage protons were assigned at about 7.45–6.74, 4.93–3.36 and 5.30–4.91 ppm, respectively. The synthesis of BPR from the reaction phenolic resins, produced under basic conditions (resoles) and boric acid was not feasible. The reactivity of the resoles species with each other is more favorable than that with boric acid.