| As the name goes “All-cellulose composite” is a monocomponent composite in that both the matrix and reinforcing agents are of the same material, cellulose. Unlike conventional composites in which the matrix and reinforcement are chemically distinct, all-cellulose composites break down the barriers and render the shortcomings incurred during the fabrication of conventional composites nonexistent as they eliminate the need for coupling agents and pretreatment of either the matrix or reinforcing agents to promote better adhesion at the matrix-filler interface.This study compares an environmentally friendly method(enzyme hydrolysis-ultrasonic treatment) for the isolation of cellulose nanofibrils(CNFs) from an agricultural waste, banana rachis and its chemical counterpart, acid hydrolysis coupled with subsequent ultrasonication. The furnished CNFs were characterized to evaluate their suitability as a reinforcement fillers(CNFs) in composites by Transmission Electron Microscopy(TEM) that proved whether the fibrils were in nanoscale dimensions, Scanning Electron Microscopy was used to investigate the morphological changes to the fibers during each stage of treatment, Dynamic light scattering provided information about the length and charge of CNFs, X-ray diffraction elucidated differences in crystallinity between the virgin fibers, acid hydrolyzed(AH-CNFs) and enzyme hydrolyzed(EH-CNFs) cellulose nanofibrils and Fourier transform Infra-red spectrometry(FTIR) was used to study the efficiency with which the pretreatments andhydrolysis methods removed the buttressing impurities(lignin, hemicellulose, waxes, pectins and minerals) around the fibrils to liberate the desired cellulose nanofibrils.TEM results showed that the CNFs obtained by both acid and enzyme hydrolysis were in nanoscale dimensions with diameters of 13±3.03 and 16±3.46 nm and length of 746.8 ±116.1nm and 985.6±136.1nm for CNFs isolated by AH and EH respectively. The aspect ratio of all the samples lay in the range of long fibrils(57.4?61.6). XRD studies revealed that AH afforded more crystalline cellulose Nano-fibrils(58.5%) as compared with EH(48.83%). FTIR spectra showed that AH-CNFs contained less lignin than both the untreated fibers and EH-CNFs. TGA and DTG thermograms showed that AH-CNFs were more thermally stable than both the bran and EH-CNFs.In the second phase of the study cellulose nanofibrils obtained by acid hydrolysis of banana rachis fibers were incorporated in a matrix of regenerated cellulose. Cellulose was regenerated in a mixture of 8% wt. Lithium chloride/N, N-dimethylacetamide(Li Cl/DMAc). All cellulose composites with different concentration of CNFs were obtained by varying the mass of fillers dispersed in the regenerated matrix to obtain thin composite films with 0, 5, 10, 15 and 20% content of CNFs. The all-composite films were then characterized to investigate the reinforcing effect of CNFs using a universal tensile tester, optical transmittance of the films was measured using UV-Vis spectrometry, thermal properties were assessed by thermal-gravimetric analysis(TGA), and crystallinity was determined using X-ray diffractometer(XRD). Characterization of the composite thin films provided the following results: On incorporating of the CNFs in the regenerated cellulose matrix there was an improvement in the mechanical properties marked by an increase of the stress at break from 35.53 to 66.45 MPa for 0 to 20 wt% CNFs content respectively, this consequently made the films more stiff which is reflected by the increase in young's modulus from 0.68 to 3.25 GPa and a huge reduction in strain to fail from 47.63 to 16.8%. Optical transmittance decreasedwith increasing CNFs content, from 86.88-68.11% when the CNFs loading was increased from 5-20% respectively. This study provided a promising method for manufacturing high performance and environmentally friendly all-cellulose nanocomposites employing an alternative source of CNFs, Banana rachis. |
PDF Full Text Request