Condensation-addition-type resole resins with phenyl ethynyl functions: Synthesis, characterization, and thermal properties

Novel phenolic resins bearing methylol and phenyl ethynyl functions and cur ing by both condensation and addition mechanisms were synthesized by the re action of 3-(phenyl ethynyl) phenol (PEP) with formaldehyde under alkaline conditions. Resins with varying relative concentration of the two functiona l groups were synthesized and characterized. The resins underwent a two-sta ge cure, confirmed by both DSC and DMA analyses. The low-temperature cure d ue to methylol condensation led to early gelation of the system. The ultima te curing through addition reaction of phenylethynyl group required heating at 275 degreesC. The cured resins exhibited better thermal stability and a naerobic char yield in comparison to a conventional resole. The thermal sta bility and char-yielding property showed a diminishing trend with enhanced methylol substitution. Resin with F/P ratio less than unity offered excelle nt thermal stability and anaerobic char yield. The thermal degradation of t he cured resins occurred in two kinetic steps. Methylene groups favored the initial degradation, whereas the higher temperature carbonization process was independent of the network structure. (C) 2001 John Wiley & Sons, Inc.