Continuous High‐Efficiency Treatment and Process Optimization of Pultruded Plant Fiber Reinforced Composites for Structural Applications

ABSTRACT The construction application of plant fiber reinforced composites (PFRCs) is hindered by poor interfacial compatibility and high flammability. An integrated approach was presented in this study to simultaneously enhance the efficiency and mechanical and fire‐retardant properties of pultruded sisal fiber‐reinforced composites (SFRCs) through a continuous pre‐treatment system. First, a novel continuous surface modification system was developed, featuring full‐fiber impregnation, precise thermal control, and in‐line tension monitoring. Second, an optimized processing window was established with the aid of orthogonal experiments and response surface methodology. Key mechanistic insights were revealed, including nonlinear concentration‐speed compensation, reversed sensitivity shifts, and a distinct thermal stabilization window. Finally, a dual‐phase flame‐retardant system was implemented to improve the fire‐resistance performances of pultruded SFRCs. The results demonstrated a remarkable improvement in pre‐treatment efficiency compared with the conventional soaking method, reducing the processing time by 83.33%. Compared with untreated yarns, the continuously treated ones exhibited an 18.62 MPa interfacial shear strength (+37.12%) and an impregnated tensile strength of 311.62 MPa (+9.06%). After flame‐retardant modification, the dual‐phase system (DMMP+MCA) effectively compensated for the mechanical degradation caused by DMMP alone, restoring the flexural strength and modulus by 24.00% and 37.06%, respectively, while the interlaminar shear strength increased by 20.29%. Meanwhile, the limiting oxygen index (LOI) rose to 34.8% (V‐0 rating). The synergistic mechanism involves enhanced surface fibrillation, polarity matching, and gas/condensed‐phase flame inhibition. This work provides a scalable, high‐efficiency manufacturing route for producing mechanically robust, flame‐retardant, and sustainable PFRCs, bridging the gap between lab‐scale innovation and industrial application.