Lignin Biobased Eco-Friendly Dipping System for Polyimide Fiber and Its Interface Adhesive Mechanism with Rubber

Fiber-reinforced rubber materials find extensive applications in tire manufacturing, hoses, conveyor belts, and various industrial sectors. Polyimide (PI) fibers offer superior fatigue resistance, tensile strength, modulus, and high-temperature durability compared to aramid fibers, positioning them as ideal substitutes in the belt layers of aircraft tire. To enhance the interfacial adhesion between polyimide fibers and rubber while minimizing the use of toxic and environmentally harmful materials, a novel eco-friendly carbon-reducing dipping system was devised. This system employs blocked diisocyanate and epoxy resin to activate PI fibers, and then uses a dipping solution, primarily composed of a blend of styrene–butadiene–vinylpyridine (VP) latex, lignin, tannic acid (TA), and glyoxal, to dip the fibers. This approach connects PI fibers and the rubber matrix through chemical bonds, thereby effectively enhancing the interfacial adhesion between the fibers and the rubber. The H pull-out force of the PI fiber cords treated by this system reached 179.6 N, with an average 180° peeling force of 14.7 N, and dynamic fatigue resistance exceeding 67,000 cycles, comparable to those achieved with the resorcinol-formaldehyde-latex (RFL) dipping system. These results indicate the efficacy of the developed system as a potential replacement for the RFL system. This research presents a sustainable and environmentally friendly approach to enhancing the interfacial adhesion of fiber-reinforced rubber composites, thereby contributing to the advancement of innovative high-performance fibers and biobased dipping system.