Physicochemical characterization of nanofiber of different treatment on Kenaf bast fiber

摘要

Two different processing (chemical and mechanical treatment) for nanofibering Kenaf {Hibicus cannabinus L.) bast fiber were investigated. In the chemical treatment cellulose whiskers prepared by hydrolysis of kenaf bast fiber with 4 N HCI at 80 °C for 4 h, followed by thorough removal of acid by repeated centrifugation and dialysis, whereas the mechanical technique involved refining, grinding and followed by high-pressure homogenizer. The structure of the cellulose nanofibers was investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The cellulose whiskers were determined to have diameters in the range of 10-80 nm and lengths of a few thousand nanometers. In comparison with, the mechanical treatment nanofibers had diameter 30-150 nm and longer lengths than the cellulose whiskers. The chemical compositions analysis, FT-IR, XRD results indicated that the hemicelluloses and lignin were removed extensively in the cellulose whiskers, with a crystallinity of 82 %. FT-IR spectroscopic analysis of the nanofiber from mechanical treatment demonstrated that this chemical treatment also led to partial removal of hemicelluloses and lignin from the structure of the fibers with a crystallinity of 75 %, whereas crystallinity raw kenaf fiber has 48%. The cellulose whisker has the higher the thermal stability than the cellulose nanofibrils. The degradation temperature of both nanofiber types reached beyond 290 C. This value is reasonably promising for the use of these nanofibers in reinforced-polymer manufacturing. The nanocomposites were produced using the cellulose whiskers and nanofibers as reinforcement with polyvinyl alcohol (PVA) as the matrix. The morphology and thermal properties of the composites were investigated by scanning electron microscopy (SEM) and TGA. The dynamical mechanical properties of the composites were compared with those of the neat polymer matrix and found to be considerably improved. Furthermore, the Kenaf nanofibers (chemical and mechanical treatment) were shown to have reinforcing capability for PVA polymers.