Preparation, Characterization And Applications Of Biocomposites Consist Of Chitosan Dispersed In Epoxidized Natural Rubber
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Date
2016-04
Authors
Idrees Mahmood, Luqman
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Biodegradability of chitosan (CTS) is relatively very high as compared to that of epoxidized natural rubber (ENR). Biocomposites containing CTS and ENR would likely to biodegrade desirably and are suitable for controlled release of compounds of interest. In view of this, acidified chitosan (CTSAc) was prepared using 2% acetic acid solution and then different loadings of CTSAc were dispersed in matrices of ENR50 and ENR25 to produce biocomposites designated as zphrCTSAc-d-ENR50 and zCTSAc-d-ENR25, respectively, wherein z refers to CTSAc loadings of 1.5, 2.5, 3.5, 5, 10, 15, 20 and 40 phr. The starting polymeric materials and resulting biocomposites were characterized using several analytical techniques such as FT-NMR spectroscopy, FT-IR spectroscopy, TGA, DSC, SEM and BET. Results of the analysis of FT-IR, TGA and DSC data reveal that CTSAc was not grafted to but dispersed widely in partially crosslinked matrices of ENR50 and ENR25. Swelling behavior of the biocomposites in water, chloroform, toluene and kerosene was investigated. The uptake of water is found to increase with the increased of CTSAc loading whereas the uptake of the organic solvents increased rapidly with chitosan loading up to 2.5 phr and then decreased with further increased of CTSAc loading. The observed general swelling behavior of the biocomposites in water and organic solvents is in accordance to the increased in the hydrophilicity of the matrices of ENR25 and ENR50 with the increased in CTSAc loading. The unprecedented finding pertaining to the rapid increased in uptake of the organic solvents particularly by 2.5phrCTSAc-d-ENR50 and 2.5CTSAc-d-ENR25 is attributable to the large internal surface area due to the presence of numerous internal voids formed by the shrinkage of the widely dispersed submicron and possibly nano size entities of CTSAc during the drying process. Cross-sectional SEM images and BET value for 1.5phrCTSAc-d-ENR50, 2.5phrCTSAc-d-ENR50, 3.5phrCTSAc-d-ENR50 and 5.0phrCTSAc-d-ENR50 is 0.308, 1.539, 0.909 and 0.561, respectively, support this finding. The biodegradation of 2.5phrCTSAc-d-ENR50 in black humus soil occurred slowly and continuously within 6 months. For controlled-release study, four different biocomposites (2.5phrCTSAc-d-ENR50, 5.0phrCTSAc-d-ENR50, 2.5phrCTSAc-d-ENR25 and 5.0phrCTSAc-d-ENR25) loaded with known amount of 1- or 2-naphthol were prepared. The amount of 1- or 2-naphthol released into aqueous media at 25 ˚C was monitored daily by means of UV-Vis spectroscopic technique up to 30 days. It is found that the release rate of 1- and 2-naphthol was gradual and independence of their solubility in water. The use of 2.5CTSAc-d-ENR25 and 2.5CTSAc-d-ENR50 for the removal of emulsified organic solvents (EOS) was investigated by means of fixed-bed column. Single solvent system (m-xylene and chlorobenzene) and binary solvent systems (chlorobenzene/m-xylene and chloroform/m-xylene) were used as simulated pollutants in water. It is found that the biocomposites can absorb (remove) 93.5 – 99.5% of the EOS from both single and binary systems even after 5 regenerations (i.e., after drying and reusing of the biocomposites). Mathematical models were used in order to know the kinetics and diffusion mechanism of the solvents absorbed by the biocomposites. Pseudo-second order kinetics and pseudo-Fickian diffusion mechanism were obeyed. Furthermore, the fixed bed adsorption data fits well with Langmuir, Freundlich and Polyani isotherm models suggesting heterogeneous coverage by the solvent molecules at outer surface of the biocomposites.
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Keywords
Chitosan