Study of Dielectric and Thermal Conductivity Properties of Recyclable Epoxy Resin Reinforced with SiO2-Coated Poly(p-phenylene benzobisoxazole) Fibers

Epoxy resins are widely used in electronic packaging and electrical insulation, but their permanent cross-linked networks and low intrinsic thermal conductivity restrict material recycling and heat dissipation. In this work, a recyclable epoxy composite was developed by combining a dual-dynamic epoxy network with silica-coated poly(p-phenylene benzobisoxazole) fibers. The composite architecture integrates thermally activated network rearrangement, amine-induced matrix degradation, electrically insulating fibrous heat transport, and recovery of the reinforcing phase within a single material system. The silica-containing coating modified the PBO-fiber surface morphology and fiber/matrix interphase, while increasing fiber content produced a progressive increase in thermal conductivity. At a fiber content of 12 wt%, the composite exhibited a thermal conductivity of 0.267 W/(m·K), together with low dielectric loss and a balance among thermal, dielectric, and mechanical properties. After hot-press reprocessing, the composite retained 92.1% of its original thermal conductivity. Immersion in n-hexylamine resulted in macroscopic disintegration of the epoxy matrix, enabling recovery of PBO@SiO2 fibers that retained their overall morphology and surface Si distribution. These results establish the composition–property relationships of a recyclable, thermally conductive, and electrically insulating fiber-reinforced epoxy composite. This work provides a feasible strategy for designing recyclable epoxy composites with balanced thermal conductivity, dielectric reliability, and fiber recoverability.