Heat and fire-resistant nanofiber networks: Towards tailoring the new generation of lightweight intermeshing polymer composite systems

Safe use of materials is a primary focus of emerging low-carbon industry. Catastrophic fire incidents due to high flammability of polymers as versatile materials necessitate developing fire-proof polymer composites. In this study, a novel and robust strategy is implemented to fabricate non-flammable and fire-proof thermoplastics with remarkably lower flame retardant (FR) content leading to outstanding limiting oxygen index (LOI) of 30% and UL 94-V0. This can be achieved using nano-fibrillation by forming networks of heat-resistant polymeric nano -fibers (polyphenylene ether (PPE) or polyphenylene sulfide (PPS)) within polystyrene (PS). Formation of heat -resistant nanofibers creates a continuous network-structured layer/shield to preserve the matrix against burning and suppresses dripping by boosting the melt-strength. Nanofibers also lead to promoting a graphitized char layer to thoroughly protect the polymer against fire. These synergistic effects enhance FR efficiency, as demonstrated by a 30% reduction in fire growth rate and peak heat release rate, upon inclusion of 15 wt% PPE nanofibers, compared to an equivalent composite with spherical particles. Only the PS sample containing 25 wt% FR and 15 wt% heat-resistant nanofibers meets UL 94-V0 while presence of a similar content of spherical PPE or PPS, graphene nanoparticles, or carbon nanotubes does not provide this feature. Nanofibers also strengthen energy absorption leading to high impact strength of PS composites (120%). Hence, this novel strategy can be extended to a wide range of polymer systems to fabricate novel generation of fire-proof devices with tunable properties for various potential applications including energy storages packs, electronic equipment, and robotics.