Laccase/TEMPO-mediated graft hydrophobization of jute fibers to enhance the mechanical properties of jute/PLA composites

In this work, the hydrophobization of lignocellulosic jute fibers was achieved via the laccase/TEMPO-mediated grafting of octadecylamine (OA) on their surface, with the aim to improve the interfacial compatibility with nonpolar polylactic acid (PLA) resins in fiber-reinforced composites. The modified jute fibers were analyzed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). The characteristic vibrations of methylene groups and the increase in the surface C/O ratio of the jute fibers after the enzymatic treatment indicated that OA molecules were successfully grafted onto the jute fiber surface mediated by the laccase/TEMPO system. It was shown that the grafted jute fibers had increased surface hydrophobicity and reduced polarity with water contact angle of 124.2 °, diiodomethane contact angle of 94.1 ° and surface free energy of 11.44 mJ/m2, which were attributed to the presence of the OA nonpolar alkyl chains on their surface. The tensile, bending, and dynamic mechanical properties of the hydrophobized jute/PLA composites were enhanced, which suggested stronger interfacial adhesion between the jute fibers and the PLA matrix. The mechanical stability was investigated by water immersion measurements and it was found that the modified jute/PLA composites were better in this regards than the control jute/PLA composites. Therefore, this enzymatic hydrophobic modification could be used as an effective and eco-friendly method to produce natural lignocellulosic fiber-reinforced composites with excellent performance
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