Coconut fibre for the synthesis of microfibrillated cellulose: Thermal analysis experimental characterization

Abstract

Fibrillated cellulose at nano‐ and microscales was obtained from green coconut fibre. The biomass was subjected to mechanical treatment (comminution and sieving of the fibres) and chemical treatment (washed with water, treated with sodium hydroxide, bleached with sodium chlorite, and subjected to acid hydrolysis). Finally, purification steps included centrifugation, dialysis, and ultrasound. The product obtained by acid hydrolysis, the crude fibre, and the intermediate‐treated samples were examined by scanning electron microscopy (SEM) and characterized by chemical analysis and thermogravimetry (TGA/DTG). The chemical characterization for crude coconut fibre demonstrated 27.99% ± 1.98% for cellulose, 14.11% ± 4.44% for hemicellulose, 25.15% ± 0.04% for lignin, and 19.34% ± 0.02% for ashes. The applied pretreatment used to remove hemicellulose and lignin from the crude coconut fibre permitted obtaining high levels of cellulose, such as 94.94% ± 5.46% for the hardest condition, with NaOH 11% (w/v)/NaClO₂. Then, acid hydrolysis was used to obtain the micro‐scale cellulose structures with 50% H₂SO₄ at 45°C for 90 min in an agitated condition (100 rpm). Following pretreatment with 2% and 11% NaOH/NaClO₂, respectively, microfibrillated cellulose was verified at levels of 0.9% and 0.75% by thermogravimetric analysis, while the commercial sample had a verification level of 1.89%. The produced micro cellulose was fibrillated with a diameter equal to 149.39 ± 40.63 nm and a length of 1764.07 ± 1109.18 nm, as determined by SEM.