Polyimide porous thermoelectric fibers based on sheath core structure: A new self-powered material for early fire warning and flame retardant protection

The integration of early warning and thermal protection functions in fire-prone environments remains a significant challenge in the development of intelligent protective textile materials. In this study, a structural regulation strategy is proposed, leveraging the synergistic templating and stress-orientation effects of carbon nanotubes (CNT) and Ag₂Se nanorods to successfully construct a polyimide (PI)/pre-oxidized polyacrylonitrile (panof)/CNT/Ag₂Se composite porous fiber (PPCAF) featuring a stable sheath–core architecture. The core, composed of a dense panof/CNT/Ag₂Se_(s) phase, offers thermal responsiveness and mechanical support. The shell comprises a porous PI matrix that buffers stress, insulates heat, and prevents Ag₂Se degradation and shedding, thereby enhancing thermal conversion and signal stability. This rational architecture enables the fiber to rapidly respond to fire-induced thermal stimuli, achieving a maximum thermoelectric voltage of 4.5 mV within 1.8 s via the Seebeck effect, ensuring stable self-powered fire warning. Concurrently, the fiber exhibits excellent passive protection, including high tensile strength (18.93 MPa), flame retardancy (LOI: 55.6 %), low thermal conductivity (0.0298 W/m·K), and superhydrophobicity (contact angle: 160.2°). These integrated properties contribute to slowing flame spread, minimizing heat transfer, and blocking moisture intrusion. This study provides both theoretical insights and practical guidelines for designing advanced self-powered intelligent textile materials with dual fire protection functionalities.