The composite double-layered films, for the packaging application of postharvest fruits and vegetables, were prepared by laminating low-density polyethylene (LDPE) and poly[styrene-b-(ethylene-co-butylene)-bstyrene] (SEBS) modified with zeolite ZSM-5. The film was characterized by scanning electron microscope and differential scanning calorimeter and tested for permeation of ethylene (C 2 H 4 ), oxygen (O 2 ), carbon dioxide (CO 2 ), and water vapor. It was found that the C 2 H 4 permeability of the films was improved because of an enhanced adsorption of C 2 H 4 by the incorporated zeolite (0-10 wt%). The preconcentrated layer (zeolite/ SEBS) leads to a higher C 2 H 4 concentration gradient across the film. Moreover, the high dispersion of zeolite increased the C 2 H 4 permeation. When compared with O 2 and CO 2 , the composite films were more selective to C 2 H 4 . However, the C 2 H 4 permeation decreased in the presence of O 2 because of a competitive adsorption. In addition, the films possessed appreciate tensile properties for packaging application.
Gas permselective plastic films have been in a great deal of attention in the area of modified atmosphere packaging of fresh produces. Such films must allow transport of the respiring gases, i.e. oxygen and carbon dioxide, in a controlled manner and, moreover, should efficiently remove ethylene gas. Therefore, the development of highly permeable films with high ethylene permselectivity, i.e. high in both permeability and selectivity, was carried out. The concept of 'mixed matrix membrane', by which enhanced gas permselectivity can be obtained by incorporation of zeolite particles into the polymeric film, was applied. Fine particles of hydrophobic zeolites, i.e. zeolite beta and ZSM-5, and the surface-modified zeolites were used in this study. The films with uniform distribution of zeolite particles (10% w/w) in 70LDPE/30SEBS (styrene-b-(ethylene-ran-butylene)-b-styrene block copolymer) matrix can be prepared by blow film extrusion. Significantly high ethylene permselectivity, i.e. ethylene permeability of 1.78-2.67 × 10 3 cm 3 • mm/m 2 • day • atm and ethylene/O 2 selectivity of 4.67-8.26, was obtained from the films containing octyl-modified and phenylmodified zeolites. Particular enhancement was observed on the films containing phenyl-modified zeolites. Crystallinity of polyethylene, transition temperatures and decomposition temperature were, however, indifferent among the studied films. Nevertheless, elongation at break and toughness of the films containing surface-modified zeolites were superior. Particle-polymer interface could thus be improved.T g , LDPE: glass transition temperature of LDPE T g , EB: glass transition temperature of EB block of SEBS T m, peak : melting temperature at peak T c : crystallization temperature at a cooling rate of 10°C/min % χ c , LDPE: percentage of crystallinity of low-density polyethylene T d : decomposition temperature at maximum derivative of weight loss 770A. FUONGFUCHAT ET AL. Figure 6. Tensile properties of 70LDPE/30SEBS films containing 10% w/w unmodified/surfacemodified zeolites. 772A. FUONGFUCHAT ET AL.
3-Acetylpyridine (AcP), as an organic hydrogen carrier, and Pd nanoparticles, as a catalyst, were incorporated into MIL-101(Cr) for chemical hydrogen storage. AcP was first grafted into MIL-101(Cr), and then Pd (0.5–4.0 wt %) was encapsulated by a double-solvent adsorption process. Thermogravimetric analysis, inductively coupled plasma–optical emission spectrometry, X-ray photoelectron spectroscopy, transmission electron microscopy, in situ X-ray adsorption near-edge structure analysis, 1H nuclear magnetic resonance (NMR), and elemental analysis suggested the existence of AcP and Pd nanoparticles (NPs) inside the MIL-101(Cr) cages. The chemical hydrogen storage of samples was evaluated by H2 temperature-programmed reaction. In situ Fourier transform infrared and 1H NMR techniques verified the hydrogenated and dehydrogenated forms of AcP upon hydrogen uptake. Reversible hydrogenation/dehydrogenation can be readily regulated by H2 partial pressure and temperature. The chemical hydrogen storage could be accomplished only when AcP and Pd NPs were adjacently present. The chemical hydrogen storage was enhanced with an increased Pd loading up to 0.33 mmol H2·g–1 per cycle. With the manipulation of hydrogenation and dehydrogenation temperatures at 150 °C, the chemical hydrogen storage can be maintained for up to 10 cycles. The material reported herein is one of the noncryogenic chemical hydrogen storages that can be operated at constant temperature and atmospheric pressure.
Highly stable Pd2+ species were anchored in ethylenediamine-grafted on MIL-101(Cr). The ethylenediamine (0.3-1.2 mmol/g) was first grafted onto MIL-101(Cr), then Pd2+ (0.03-0.2 mmol Pd/g) was incorporated by double-solvent adsorption. Fourier...
The CO 2 and CH 4 permeabilities of poly(ethylene-co-vinyl acetate) (EVA)/ SiO 2 composite membrane were investigated at atmospheric pressure. The membranes were fabricated by compression molding and characterized by Fourier transformed infrared spectroscopy, differential scanning calorimetry, a universal testing machine, and a contact angle analyzer. The effect of vinyl acetate content (18-33 wt%) was evaluated for both single-gas and mixed-gas permeation systems. A non-pressurized homemade-permeation cell was used for the single-gas permeation of CO 2 and CH 4 , while a tubular membrane was utilized for a continuous separation of CO 2 /CH 4 mixture. CO 2 flux was readily increased (from 0.7 to 2.0 ml/m 2 .s) with vinyl acetate content (18-33 wt%). The enhanced CO 2 permeability is attributed to the increase in polarity and also the decrease in crystallinity of the membrane. A satisfied gas separation selectivity (CO 2 /CH 4 ) of 4.31 could be obtained from tubular membrane with 28 wt% VA content. The incorporation of SiO 2 as a filler (0.5-2.0 wt%) especially increased the membrane polarity and hence the CO 2 flux up to 6.0 ml/m 2 .s. However, the CH 4 flux was not affected by VA and SiO 2 contents.
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