Synthesis and characterization of phenolic resole resins for composite applications

Abstract

In this study, phenol–formaldehyde resins catalyzed with sodium hydroxide, triethylamine, and ammonium hydroxide were investigated and characterized in terms of their degradation behavior, flammability, mechanical properties, and chemical structure. All three resins displayed similar degradative mechanisms, and their degradation behavior was broken down into three distinct stages. These stages were attributed to the evolution of water, the volatilization of species loosely bound to the phenolic backbone, and bulk degradation of the phenolic matrix. Flammability studies were also performed on glass fiber laminates manufactured from these resins. The sodium-hydroxide- and ammonium-hydroxide-catalyzed resins were found relatively inflammable, while the triethylamine-catalyzed laminates burned readily. The mechanical properties of the resins were found to be similar or higher than the mechanical properties of other untoughened epoxies or thermosetting resins. The various chemical properties responsible for these behaviors are discussed and analyzed in terms of the catalyst basicity, solubility, and boiling point. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 505–514, 1999