Mechanical properties of toughened windmill palm fibre with different chemical compositions.

Windmill palm fibres are well-known plant fibres exhibiting the largest elongation at break. In this study, lignin or hemicellulose was removed from windmill palm fibres in a targeted manner to prepare materials with different chemical compositions. The structure and mechanical properties of the windmill palm fibres were analysed using in situ scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry, X-ray diffraction analysis and tensile testing. The large elongation at break was attributed to the unwinding of the single fibre, the micro cracks and the small degree of orientation (<62 %). On a microscopic scale, the lumen shape of fibre cross section influences the local stress distribution. The hemicellulose-removed fibres exhibited a high breaking strength of 236 MPa with deterioration of the thermal property. The binding force between single fibres is the weakest after lignin removal. The removal of hard lignin softens the fibres and increases the elongation at break to >30 %.