Mechanical and Water Absorption Properties of Short Banana Fiber/Unsaturated Polyester/Molecular Sieves + ZnO Nanorod Hybrid Nanobiocomposites

ZnO nanorods were prepared by the sol-gel method and characterized using UV-visible absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), thermogravimetric analysis/differential thermogravimetry (TGA/DTG), high-resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDAX). Banana fiber/polyester resin (BF/PE) biocomposites and BF/PE/MS/nano ZnO nanobiocomposites were made using the untreated and chemically treated (with NaOH, formic acid, acetic anhydride, hydrogen peroxide, and potassium permanganate) banana fiber (BF), unsaturated polyester resin (PE), molecular sieves (MS), and the prepared ZnO nanorods. The KMnO, AcO, and NaOH treatments enhanced the thermal stability of the nanobiocomposites. Addition of 2% of ZnO nanorods increased the tensile strength of all of the chemically treated BF/PE/MS biocomposites. The chemical treatments alone decreased (NaOH-15.4 MPa; KMnO-14.5 MPa; HO-9.9 MPa; AcO-7.9 MPa; HCOOH-6.9 MPa) the compressive strength of the untreated BF/PE/MS biocomposite (25.9 MPa). But the chemical treatment and addition of ZnO nanorods enhanced the compressive strength effectively (48.5, 41.6, 39.4, 37.0, and 34.6 MPa for NaOH, HCOOH, KMnO, HO, and AcO treatments, respectively) compared to the untreated BF/PE/MS biocomposites (24.0 MPa). The HO (69.0 MPa) and NaOH (62.9 MPa) treatments enhanced the flexural strength of the untreated BF/PE biocomposites (51.6 MPa). The addition of ZnO nanorods enhanced the flexural strength of all of the chemically treated (except NaOH) BF/PE/MS biocomposites (55.7, 59.4, 79.0, and 67.4 MPa for HCOOH, AcO, HO, and KMnO treatments, respectively). The impact strengths of the biocomposites were enhanced by both chemical treatments and addition of ZnO nanorods. The addition of ZnO nanorods decreased the water absorption of the biocomposites significantly from 24.3% for the untreated to a minimum of 14.5% for the HO-treated BF/PE/MS/ZnO nanobiocomposite.