Preparation and Microwave Curing of Blended Phenolic Epoxy Fibers

Phenolic fibers are a new type of heat-resistant organic fiber material prepared through spinning. They are made of phenolic resin and are spun and cured to obtain corrosion-resistant, high-temperature heat-insulating, smokeless, nontoxic fibers. Pure phenolic fibers have limitations in some applications due to their poor toughness and brittleness. Therefore, the improvement of the toughness of phenolic fibers and spinning has become the focus of research. In this work, phenolic fibers with an elongation at break of 8.7% and a breaking strength of 162.5 MPa were obtained by spinning epoxy-toughened phenolic resin. First, a high-ortho thermosetting phenolic resin solution (TPRS) was synthesized and blended with the phenolic epoxy resin F-44. Subsequently, as-spun fibers were prepared through dry-spinning. Finally, the as-spun fibers were subjected to microwave curing (MC). The effects of different TPRS : F-44 ratios and MC durations on the mechanical properties of the fibers were systematically investigated. Experimental results showed that under microwave conditions at a curing power of 80 W, the optimal mass ratio of TPRS : phenolic epoxy resin was 50 : 12 and the optimal curing time was 8 min. After the curing reaction, a large amount of hydroxymethyl groups was generated. During curing, the hydroxymethyl groups generated additional methylene bridges and epoxy groups underwent ring-opening reactions. Finally, a reticulated polymer was generated.