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

In this work, the hydrophobization of lignocellulosic jute fibres 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 (PLA) resins in fibre-reinforced composites. The
modified jute fibres 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 fibres after the
enzymatic treatment indicated that OA molecules were successfully grafted
onto the jute fibre surface mediated by the laccase/TEMPO system. It was
shown that the grafted jute fibres 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 fibres 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 fibre-reinforced composites with
excellent performance.