Morphology, crystallinity and thermal properties of nanocrystalline cellulose isolated of sisal fiber by acid hydrolysis-ultrasonication

Nanocrystalline cellulose (NCC) from natural Agave sisalana (Sisal) fibers were isolated using a combination of chemical and mechanical processes. The chemical treatment begins with soaking the fiber in a sodium hydroxide (NaOH) solution with a concentration of 5 wt.% at a temperature of 90°C for 60 minutes. Then following by bleaching (fiber refining) using a hydrogen peroxide solution (H2O2) with a concentration of 3 wt.% (weight), at a temperature of 60°C, and pH of 10 for 30 minutes. It aims to eliminate the presence of hemicellulose and lignin contained in the fiber. Fibrillation Micro into nano Sisal fibers using sulfuric acid (hydrolysis process). Sulfuric acid (H2SO4) with 55 wt.% at temperature 60°C for 30 minutes produced NCC with a diameter of 5±1 nm (D) and a length of 260±10 nm (L), as seen using a TEM (transmission electron microscope). The web-like network structured shape of NCC results in a high aspect ratio (L/D) value is 52. The acid hydrolysis-ultrasonication process produced a high crystallinity index of 78.82% through the XRD (x-ray diffraction) test. The crystallinity and aspect ratio of NCC show that Sisal fiber is a suitable material as a filler for bio-nanocomposite materials. The maximum temperature (Tmax) of NCC decreased by 10°C due to sulfate ions attached to the cellulose structure, causing the thermal stability to drop from 348°C to 338°C.