Mechanical and High-Temperature Properties of Glass Fibers Reinforced Phenolic Composites

Abstract

This article discusses the mechanical and high-temperature performances of four glass fibers reinforced phenolic resins composites, which were a pure resol resin (no curing agent, named Resol), a pure novolac resin (cured with 10% hexamethylenetetramine, HMTA, named Novolac), a blend resin (50% resol and 50% novolac, named Blend), another blend resin (47.5% resol, 47.5% novolac, and 5% HMTA, named Blend1). Dynamic mechanical analysis (DMA) was used to investigate the curing properties of the materials, while fiber-matrix adhesion and wetting characteristics were studied by scanning electron microscope (SEM). The Blend and Blend1 composites had more loosely crosslinked structures compared with the pure Resol or Novolac composite. Moreover, the Blend, Blend1 and Resol composites had better adhesion and wetting properties with glass fibers than those of the Novolac composite, so the Blend and Blend 1 resins were prepared to obtain phenolic composites with improved impact and flexural strength, without degeneration of their high-temperature performance. On comparing the Blend1 composite held higher crosslink density and more regular crosslink structure than those of the Blend composite, which resulted in the Blend1 composite had better mechanical and high-temperature performances. It was also found that the crosslink density and the interfacial bonds between the fibers and the resin matrix of the materials could be increased by postcure, which produced an increase in their mechanical and high-temperature properties.