Isolation And Characterization Tempo Oxidized Nanocrystalline Cellulose From Oil Palm Empty Fruit Bunch
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Date
2015-09
Authors
Roslan, Rohaizu
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Abstract
Oil palm empty fruit bunch nanocrystalline cellulose (OPEFB-NCC) has been successfully isolated, with yields of 67%, from OPEFB-MCC via a chemical and mechanical process using 4-acetamido-TEMPO/NaBr/NaClO oxidation and ultrasonic treatment. TEM images indicate the morphology of OPEFB-NCC as straight crystals of cellulose with lengths 122 ± 45 nm, and uniform widths of 4 ± 2 nm. FTIR and 13C-NMR/MAS solid state analysis suggests that oxidation occurred at the site of the primary (C6) hydroxyl groups on the cellulose chain and that OPEFB-NCC consists primarily of crystalline cellulose I. XRD and 13C-NMR/MAS indicated that OPEFB-NCC had a lower crystallinity index than the OPEFB-MCC starting material. Thermal analysis revealed that OPEFB-NCC degraded at lower temperature than OPEFB-MCC, but had a much higher char content of 46% to the 7% of OPEFB-MCC. The production of MCC is a chemical and time consuming process, involving various reaction steps during its preparation; hence an alternative of a much simpler material such as cellulose pulp is much desired. However, since its production also entails a sequence of bleaching process, the effect of such sequence on the properties of TO-OPEFB pulps were also investigated. Based on the carboxyl content and crystallinity of the obtained TO-OPEFB pulp, it is established that unbleached OPEFB pulp gave the same desired effect than bleached TCF pulps. NCC isolated from TO-OPEFB unbleached pulp (OPEFB-NCC-pulp) also exhibit straight crystals of cellulose with an average width of 5 ± 1 nm. Comparatively, OPEFB-NCC-pulp has a longer crystallite length with an average length of 224 ± 80 nm against 122 ± 45 nm for OPEFB-NCC-MCC. Consequently, OPEFB-NCC-pulp has a greater geometrical axial ratio; nevertheless, both types of NCC are comparable in terms of crystallinity and thermal stability. Films of OPEFB-NCC exhibit iridescence (rainbow like effect) in polarized light, which increases with film thickness but at the expense of transparency. Visual observations of the film made from low and medium geometrical axial ratios of OPEFB-NCC (with values of 27 and 45) were optically transparent, whilst the film with high axial ratio of 46 appeared translucent. When viewed under POM, film of low axial ratio induces the largest reflected color in the blue region, whilst for the medium axial ratio, it shifted to green region of the visible spectrum. With further increase to the high axial ratio, the iridescent appearance could no longer be seen. The OPEFB-NCC-pulp films also showed a smooth, transparent but brittle surface with a tensile strength of about 49 MPa, Young’s modulus of 9.26 GPa and an elongation at break of 0.53%. Glycerol was added as a plasticizer, resulting in a much more pliable film, easily bent, folded and can be cut without cracking compared to that of the pure OPEFB-NCC-pulp film. However, the plasticized OPEFB-NCC-pulp films have lower tensile properties and crystallinity, but higher wettability compared to pure OPEFB-NCC film. Taking into consideration of the positive and negative effects, it is suggested that a 30% addition of glycerol is recommended for OPEFB-NCC film production. The outcome of this study opens a new avenue and forms the basis in the research efforts on expanding the capabilities of biomass residue into nanotechnology application from biodegradable material in a safe and sustainable manner.
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Tecnology