Effect of Sodium Hydroxide Treatment on Physico-chemical, Thermal, Tensile and Surface Morphological Properties of Pongamia Pinnata L. Bark Fiber

Abstract

ABSTRACT Surfaces of Pongamia pinnata L. fiber (PPF) were modified by the 5% (w/v) sodium hydroxide solution with the various immersing period as 15, 30, 45, 60 and 75 minutes. Chemical compositional analysis evidenced that 5% (w/v) sodium hydroxide solution with 60 minute immersing period is optimum treatment. Removal of lignin content from the optimally treated PPF was detected through the chemical analysis as well as Fourier Transform-Infrared spectroscopy. X-ray diffraction analysis outcomes established the enhancement in the crystallinity index (45.31% to 52.43%) and crystallite size (5.43 nm to 8.32 nm) of the optimally surface-modified PPF. Improvement in the maximum cellulose degradation temperature (332°C to 348°C) and kinetic activation energy of the optimally-surface modified fibers (68.642 KJ/mol to 72.563 KJ/mol) were acknowledged from differential thermogravimetric curve and broido plots. Scanning electron microscope and atomic force microscopy investigations visualized the improvement in surface roughness of the PPF after alkalization. All the above findings authorized the suitability of optimally surface modified PPF as reinforcement in lightweight polymer composite applications.