Effects of Grewia Bicolor (GB) Fiber Extraction Methods in the Reinforcement of a Biosourced Detarium Microcarpum(DM) Tannin Matrix Material

Abstract

This work aims to evaluate the effect of extraction methods for Grewia bicolor (GB) fiber in the reinforcement of a biosourced material with a Detarium Microcarpum (DM) tannin matrix. GB fibers were extracted by biological retting and chemical extraction in sodium hydroxide (NaOH) solutions at concentrations of 2% and 5%, respectively, and sampled from three plant zones: bottom, middle, and top. These different fiber families were physically characterized (moisture content, water absorption, density) and mechanically tested under tensile loading, followed by multivariate statistical analysis using Multivariate Analysis Of Variance (MANOVA). Tannin extracted from DM bark was characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-ToF) mass spectrometry, and its reactivity with formaldehyde was evaluated. A biosourced resin was then formulated using DM tannin and Acacia nilotica as a natural hardener. This resin was characterized by measuring hydrogen potential (pH), dry extract, and gel time. Composite panels were produced by combining the formulated resin with the various fiber families at a 30% reinforcement rate. These composites were characterized physically (water absorption, thickness swelling, density) and mechanically in terms of modulus of elasticity (MOE), modulus of rupture (MOR), and internal bonding (IB) strength. The results demonstrated that fibers extracted with 2% NaOH provided the best overall performance. MANOVA combined with Tukey's test at a 95% confidence level showed statistically significant differences among the extraction methods but not between the bottom and middle fibers regardless of the method. The characterization of DM tannin showed its potential use in resin production. The performance of the composites manufactured was better than those made with the fibers extracted in the 2% NaOH solution, showing that GB fibers and DM tannin are promising local resources for the production of furniture panels working in a dry environment in compliance with the requirements of NF EN 312.