Effect of alkaline surface treatment on the mechanical and thermal performance of polyamide 11/ramie fiber composites

In this study, a bio-based polyamide 11 (PA11) composite reinforced with alkali-treated ramie fiber (tRF) was successfully fabricated by hot pressing. To identify optimal treatment conditions, ramie fibers were subjected to alkaline treatment using NaOH concentrations of 0%, 1%, 3%, and 5% by weight. Treatment of ramie fibers with a 3% NaOH solution led to a remarkable 137.5% increase in tensile strength compared to untreated fibers, alongside improved surface characteristics and fiber purity. As a result, the PA11/tRF composite substantially improved overall performance. Specifically, tensile strength increased by 131.45% and flexural strength by an impressive 390.51% compared to neat PA11. Advanced characterization techniques, including dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), confirmed strong interfacial interactions and enhanced thermal stability of the PA11/ramie fiber composite. These outstanding results demonstrate the effectiveness of alkali-treated ramie fibers in reinforcing PA11, establishing the PA11/tRF composite as a strong candidate for sustainable, high-performance, and eco-friendly material applications.