Properties of Thermoplastic High-ortho Phenolic Epoxy Fibers

The thermoplastic high-ortho phenolic resins (HPRs) were synthesized by a one-step synthesis using phenol, formaldehyde, zinc acetate, sulfuric acid, and small amounts of ethanol. It was then blended with epoxy resins, and a small amount of ethylenediamine (EDA) was added as a curing agent for dry spinning to produce the as-spun fibers. Heat curing and microwave curing treatments were performed to obtain phenolic epoxy fibers. Using Fourier transform infrared spectroscopy to study the structural changes during the fiber curing process revealed that the amino groups in EDA opened the epoxy groups to generate the hydroxyl groups. The hydroxyl groups can further react with the epoxy groups, which accelerate the curing reaction. Thermogravimetric analysis (TGA) results showed a higher residual carbon degree in the fibers after curing. Mechanical property testing demonstrated a significant improvement in the mechanical properties of the fibers. By modifying the blending and optimizing the curing process, the heat resistance of the fibers was successfully improved, resolving the issue of poor mechanical properties in the high-ortho phenolic epoxy fibers (HPEFs).