Thermal and mechanical properties of chitosan nanocomposites with cellulose modified in ionic liquids

In this paper, ionic liquid treatment was applied to produce nanometric cellulose particles of two polymorphic forms. A complex characterization of nanofillers including wide-angle X-ray scattering, Fourier transform infrared spectroscopy, and particle size determination was performed. The evaluated ionic liquid treatment was effective in terms of nanocrystalline cellulose production, leaving chemical and supermolecular structure of the materials intact. However, nanocrystalline cellulose II was found to be more prone to ionic liquid hydrolysis leading to formation larger amount of small particles. Each nanocrystalline cellulose was subsequently mixed with a solution of chitosan, so that composite films containing 1, 3, and 5% mass/mass of nanometric filler were obtained. Reference samples of chitosan and chitosan with micrometric celluloses were also solvent casted. Thermal, mechanical, and morphological properties of films were tested and correlated with properties of filler used. The results of both, tensile tests and thermogravimetric analysis showed a significant discrepancy between composites filled with nanocrystalline cellulose I and nanocrystalline cellulose II

Enhanced ductility and tensile properties of hybrid montmorillonite/cellulose nanowhiskers reinforced polylactic acid nanocomposites

Montmorillonite (MMT)/cellulose nanowhiskers (CNW) reinforced polylactic acid (PLA) hybrid nanocomposites were prepared by solution casting. CNW were isolated from microcrystalline cellulose using a chemical swelling method. An initial study showed that the optimum MMT content, for mechanical properties, in a PLA/MMT nanocomposite is five parts per hundred parts of polymer (phr). Various amounts of CNW were added to the optimum formulation of PLA/MMT to produce PLA/ MMT/CNW hybrid nanocomposites. FT-IR analysis indicated the formation of some polar interactions, resulting in enhanced tensile properties of the hybrid nanocomposites. The highest tensile strength for the hybrid nanocomposites was obtained for a 1 phr CNW content. Young’s modulus was also found to increase with an increasing CNW content. Interestingly, the strain to failure (or ductility) of the hybrid nanocomposites increased significantly from ~10 to ~90% with the addition of 1 phr CNW. This increase in ductility was proposed to be due to the nucleation of crazes and the formation of shear bands in the PLA

Flammability and tensile properties of polylactide nanocomposites with short carbon fibers

[[abstract]]Nanocomposites of polylactide (PLA) with aluminum hydroxide (ATH), short carbon fibers (CF), and montmorillonite (MMT) were prepared via direct melt blending. The exfoliated and intercalated clay structures with some aggregations in the PLA matrix were observed. The tensile strength and elongation at break of the PLA composite caused by the high content of the retardant ATH were improved by adding modified MMT and CF to replace a portion of ATH in the PLA matrix. The thermal degradation temperatures and char residue of the PLA/ATH/MMT/CF nanocomposites as determined by thermogravimetric analysis were higher than without MMT. Furthermore, a novel method was proposed to analyze the flammability of composite using an infrared camera, which could capture the apparent thermal image of the sample during UL 94 V test. It was found that, with addition of the MMT and short CF, a more effective insulation layer could be formed on the ablating surface of the PLA/ATH composite, and the high thermal conductivity of the CF might increase the release rate of heat from the surface composite during burn, thus the PLA/ATH/MMT nanocomposite containing short carbon fibers having a V-0 rating without flaming dripping could be obtained.[[notice]]補正完