Effect of NaOH and silane treatment on short Raphia vinifera fiber bio-epoxy composites

The use of green composites is now an undeniable reality for environmental reasons, hence the choice of eco-friendly resins and reinforcements. Thus, bio-epoxy composites (SR GreenPoxy 56) reinforced with Raphia vinifera fibers (RVFs) were fabricated by contact molding, using two volume fractions (20 and 40%) and two fiber lengths (5 and 15 mm). The RVFs were considered in three forms: untreated, silane-treated, and NaOH-treated. The chemical functional groups were identified by Fourier transform infrared spectrometry (FTIR), while the thermal degradation analysis was performed by thermogravimetric analysis (TGA/TDG), and the heat capacities were determined by differential scanning calorimetry (DSC) on the silane and NaOH-treated Raphia vinifera fiber-reinforced composite (RVFC) samples. The bulk density, water absorption rate, and tensile mechanical properties were evaluated on the treated and untreated RVFCs specimens. Furthermore, Multivariate Analysis of Variance (MANOVA) and the Tukey test were used to evaluate the significant differences between the properties of different specimens. The results of chemical structure by FTIR show the formation of Si-OC and Si-O-Si bonds for the silane-treated RVFC sample, while hydroxyl groups are observed for the NaOH-treated RVFC sample. Thermal analysis by TGA shows a slightly lower thermal stability for the silane-treated RVFC compared to the NaOH-treated RVFC and is confirmed by DSC analysis on the crystallization temperatures. The density of the different silane and NaOH-treated RVFC specimens increased significantly according to MANOVA analysis compared to the untreated ones. Whereas the NaOH- and silane-treated RVFC specimens absorb significantly less water compared to the untreated ones. The tensile stress at break of various RVFC samples treated with silane increased significantly by 128% and 62% for RVFCs-20-5 and RVFCs-20-15, respectively, compared to the untreated samples. However, those treated with NaOH increased by 190% and 74% for the same samples compared to the untreated samples.