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    Enhanced CO2/CH4 Permselectivity in Partially Hydrolyzed EVA Membranes via Synergistic PEG Plasticization and Amine-Functionalized Silica Incorporation
    (2026-03-27) ;
    Wisatsuvan, Patchnakan
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    The separation of carbon dioxide (CO2) from methane (CH4) in biogas is essential for increasing the fuel quality. However, conventional membrane-based separation under high pressure is not suitable for household biogas systems due to operational cost and complexity. This study aims to develop low-pressure gas separation membranes based on partially hydrolyzed ethylene vinyl acetate (p-E) copolymers by incorporating poly(ethylene glycol) (PEG) as a plasticizer and amine-functionalized silica (APTES-modified SiO2) as a polar filler. The hydrolysis of EVA improves mechanical strength by increasing hydrogen bonding. PEG addition enhances the free volume and CO2 affinity, while the well-dispersed surface-treated SiO2 increases membrane polarity and suppresses CH4 permeation. Among the tested membranes, the optimal formulation (p-EP400(15)-S0.6) containing 15 wt % PEG400 and 0.6 wt % APTES-SiO2 achieves the highest CO2/CH4 selectivity (∼22) and a high CO2 permeability (∼1400 g/m2·day). These findings demonstrate a promising strategy to develop effective membranes for biogas upgrading under ambient conditions.
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    Tubular EVA copolymer/SiO2/PEG composite membrane for CO2 removal from household biogas
    (2025-03-01)
    Watasit, Prachya
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    Ausavasukhi, Artit
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    The fuel efficiency of household biogas is generally regulated by its CO<inf>2</inf> content (25%–50%). To improve its heating value, atmospheric CO<inf>2</inf> removal of household biogas using a polymeric membrane was attempted to avoid a complicated separation process. A tubular membrane of poly(ethylene-co-vinyl acetate), composed of 28% and 18% vinyl acetate (E28 and E18) modified with SiO<inf>2</inf> and polyethylene glycol (PEG), was fabricated by blown film extrusion. Model biogas containing CO<inf>2</inf>/CH<inf>4</inf> (40/60 v/v) was separated in an in-house continuous gas separation module, in which CO<inf>2</inf> was mainly permeated out of the tubular membrane at atmospheric pressure. Blending the E28 matrix with E18 (10 wt%) improves the membrane processability and inhibits the CH<inf>4</inf> permeation, leading to enhanced CO<inf>2</inf>/CH<inf>4</inf> selectivity (from ~2.3 to 2.9). Well-dispersed SiO<inf>2</inf> particles (0.5 wt%) increase the membrane modulus and suppress CH<inf>4</inf> loss. However, adding more SiO<inf>2</inf> (0.75–1.0 wt%) leads to higher total gas permeation flux with lower CO<inf>2</inf>/CH<inf>4</inf> selectivity due to particle agglomeration. Incorporation of PEG (0.5–1.5 wt%) increased the membrane polarity and CO<inf>2</inf> permeability. The CO<inf>2</inf>/CH<inf>4</inf> selectivity was also improved (~5.3), only up to 1.0 wt% PEG content. Highlights: Composite EVA/SiO2/PEG membrane separates CO<inf>2</inf>/CH<inf>4</inf> at atmospheric pressure. The concentration gradient across the membrane drives CO<inf>2</inf>/CH<inf>4</inf> permeation. Adding SiO<inf>2</inf> hinders CH<inf>4</inf> permeability and enhances CO<inf>2</inf>/CH<inf>4</inf> selectivity. Increasing PEG content enhances membrane polarity and interaction with CO<inf>2</inf>.
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    Improvement of water vapor permeability of LLDPE/EVA film with zeolite A as filler
    (2017-01-01) ;
    Jaisomboon, Nattarika
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    In this work, water vapor permeability of linear low density polyethylene (LLDPE)/ethylene vinyl acetate copolymer (EVA) film is improved by incorporation of zeolite A as filler (0-25%wt) for prolonging shelf-life of fresh produces. All films were characterized by SEM, DSC, tensile testing, contact angle measurement and tested for water vapor permeability (WVP). The shelf-life of Bird's eye chili in the film samples was also tested at 10°C for 21 days. It was found that zeolite A particles were virtually dispersed in EVA phase. Accordingly, crystallinity and tensile properties of LLDPE/EVA/Zeolite A films is independent to zeolite loading. Despite, when zeolite loading was increased, the dispersion became low. The film's wetting behavior was enhanced by increasing zeolite content in the LLDPE/EVA/Zeolite A films. The observed increase in the film's polarity significantly enhances the WVP. Therefore, less water condensed can be found inside the package made with LL80E20Ze25 film, as compared to LLDPE or LLDPE/EVA film. The LL80E20Ze25 also possesses comparable tensile properties to the commercial LLDPE film and hence can used as packaging for extending the shelf-life of fresh produces.
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    Selective ethylene-permeable zeolite composite double-layered film for novel modified atmosphere packaging
    (2011-01-01)
    Monprasit, P.
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    Fuongfuchat, A.
    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)-b-styrene] (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<inf>2</inf>H<inf>4</inf>), oxygen (O<inf>2</inf>), carbon dioxide (CO<inf>2</inf>), and water vapor. It was found that the C<inf>2</inf>H <inf>4</inf> permeability of the films was improved because of an enhanced adsorption of C<inf>2</inf>H<inf>4</inf> by the incorporated zeolite (0-10 wt%). The preconcentrated layer (zeolite/SEBS) leads to a higher C<inf>2</inf>H <inf>4</inf> concentration gradient across the film. Moreover, the high dispersion of zeolite increased the C<inf>2</inf>H<inf>4</inf> permeation. When compared with O<inf>2</inf> and CO<inf>2</inf>, the composite films were more selective to C<inf>2</inf>H<inf>4</inf>. However, the C<inf>2</inf>H<inf>4</inf> permeation decreased in the presence of O<inf>2</inf> because of a competitive adsorption. In addition, the films possessed appreciate tensile properties for packaging application. Copyright © 2009 Society of Plastics Engineers.
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    Atmospheric CO2/CH4 permeability of EVA copolymer/SiO2 composite membrane for biogas purification
    (2021-09-10)
    Watasit, Prachya
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    Ausavasukhi, Artit
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    The CO<inf>2</inf> and CH<inf>4</inf> permeabilities of poly(ethylene-co-vinyl acetate) (EVA)/SiO<inf>2</inf> 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%) wasevaluated for both single-gas and mixed-gas permeation systems. A non-pressurized homemade-permeation cell was used for the single-gas permeation of CO<inf>2</inf> and CH<inf>4</inf>, while a tubular membrane was utilized for a continuous separation of CO<inf>2</inf>/CH<inf>4</inf> mixture. CO<inf>2</inf> flux was readily increased (from 0.7 to 2.0 ml/m<sup>2</sup>.s) with vinyl acetate content (18–33 wt%). The enhanced CO<inf>2</inf> permeability is attributed to the increase in polarity and also the decrease in crystallinity of the membrane. A satisfied gas separation selectivity (CO<inf>2</inf>/CH<inf>4</inf>) of 4.31 could be obtained from tubular membrane with 28 wt% VA content. The incorporation of SiO<inf>2</inf> as a filler (0.5–2.0 wt%) especially increased the membrane polarity and hence the CO<inf>2</inf> flux up to 6.0 ml/m<sup>2</sup>.s. However, the CH<inf>4</inf> flux was not affected by VA and SiO<inf>2</inf> contents.