Molecular Simulations of Hydrogen Sorption in Semicrystalline High-Density Polyethylene: The Impact of the Surface Fraction of Tie-Chains.

The modeling of the barrier properties of semicrystalline polymers has gained interest following the possible application of such materials as protective liners for the safe supply of pressurized hydrogen. The mass transport in such systems is intimately related to the complex intercalation between the crystal and amorphous phases, which was approached in this work through an all-atom representation of high-density polyethylene structures with a tailored fraction of amorphous-crystalline connections (tie-chains). Simulations of the polymer pressure-volume-temperature data and hydrogen sorption were performed by means of molecular dynamics and the Widom test particle insertion method.

Permeation of Ternary Mixture Containing HS, CO and CH in Aquivion Perfluorosulfonic Acid (PFSA) Ionomer Membranes.

Aquivion E87-12S Perfluorosulfonated acid ionomer material (PFSA) has been studied as a membrane technology for natural gas sweetening from CO, HS due to its interesting chemical and mechanical stability and good separation performance for polar compounds in humid environments. In the present work, permeation of the HS/CO/CH ternary mixture in this short-side PFSA chain was investigated at pressures up to 10 bar, temperatures up to 50 °C, and in a range of relative humidity (RH) from 20% to 90%. The results obtained confirm the strong dependence of Aquivion on water activity and temperature, and its ability to separate gases based on their water solubility without substantial differences between pure and mixed gas experiments.

The use of essential oils in chitosan or cellulose-based materials for the production of active food packaging solutions: a review.

In recent decades, interest in sustainable food packaging systems with additional functionality, able to increase the shelf life of products, has grown steadily. Following this trend, the present review analyzes the state of the art of this active renewable packaging. The focus is on antimicrobial systems containing nanocellulose and chitosan, as support for the incorporation of essential oils.

Effect of Mobile Carrier on the Performance of PVAm-Nanocellulose Facilitated Transport Membranes for CO Capture.

Facilitated transport membranes obtained by coupling polyvinylamine with highly charged carboxymethylated nanocellulose fibers were studied considering both water sorption and gas permeation experiments. In particular, the effect of the L-arginine as a mobile carrier was investigated to understand possible improvements in CO transport across the membranes. The results show that L-arginine addition decreases the water uptake of the membrane, due to the lower polyvinylamine content, but was able to improve the CO transport.

Pebax 2533/Graphene Oxide Nanocomposite Membranes for Carbon Capture.

In this work, the behavior of new GO-based mixed matrix membranes was tested in view of their use as CO-selective membrane in post combustion carbon capture applications. In particular, the new materials were obtained by mixing of Pebax 2533 copolymer with different types of graphene oxide (GO). Pebax 2533 has indeed lower selectivity, but higher permeability than Pebax 1657, which is more commonly used for membranes, and it could therefore benefit from the addition of GO, which is endowed with very high selectivity of CO with respect to nitrogen.

Effect of Crystallinity on Water Vapor Sorption, Diffusion, and Permeation of PLA-Based Nanocomposites.

The effects of crystalline morphology and presence of nanoparticles such as cellulose nanofibers (CNFs), organically modified nanoclay (C30B), or a combination of both on water vapor sorption and diffusion in polylactide (PLA) were evaluated by a quartz spring microbalance (QSM). It was found that the large spherulite size induced by high-temperature processing leads to an increase in water sorption and a substantial reduction of diffusion with increasing crystallinity. Contrarily, small-sized spherulites, arising after low-temperature processing during solvent-casting, showed a different behavior with a slight decrease in both water vapor sorption and diffusion with increasing crystallinity.

Polyvinylamine Membranes Containing Graphene-Based Nanofillers for Carbon Capture Applications.

In the present study, the separation performance of new self-standing polyvinylamine (PVAm) membranes loaded with few-layer graphene (G) and graphene oxide (GO) was evaluated, in view of their use in carbon capture applications. PVAm, provided by BASF as commercial product named Lupamin, was purified obtaining PVAm films with two degrees of purification: Low Grade (PVAm-LG) and High Grade (PVAm-HG). These two-grade purified PVAm were loaded with 3 wt% of graphene and graphene oxide to improve mechanical stability: indeed, pristine tested materials proved to be brittle when dry, while highly susceptible to swelling in humid conditions.

Arginine/Nanocellulose Membranes for Carbon Capture Applications.

The present study investigates the influence of the addition of l-arginine to a matrix of carboxymethylated nanofibrillated cellulose (CMC-NFC), with the aim of fabricating a mobile carrier facilitated transport membrane for the separation of CO. Self-standing films were prepared by casting an aqueous suspension containing different amounts of amino acid (15-30-45 wt.%) and CMC-NFC.

Models for Facilitated Transport Membranes: A Review.

Facilitated transport membranes are particularly promising in different separations, as they are potentially able to overcome the trade-off behavior usually encountered in solution-diffusion membranes. The reaction activated transport is a process in which several mechanisms take place simultaneously, and requires a rigorous theoretical analysis, which unfortunately is often neglected in current studies more focused on material development. In this work, we selected and reviewed the main mathematical models introduced to describe mobile and fixed facilitated transport systems in steady state conditions, in order to provide the reader with an overview of the existing mathematical tools.

Permeability and Selectivity of PPO/Graphene Composites as Mixed Matrix Membranes for CO₂ Capture and Gas Separation.

We fabricated novel composite (mixed matrix) membranes based on a permeable glassy polymer, Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), and variable loadings of few-layer graphene, to test their potential in gas separation and CO₂ capture applications. The permeability, selectivity and diffusivity of different gases as a function of graphene loading, from 0.3 to 15 wt %, was measured at 35 and 65 °C.

Effect of relative humidity on the gas transport properties of zeolite A/PTMSP mixed matrix membranes.

Increasing the knowledge of the influence of water vapor in new mixed matrix membranes (MMMs) could favor the integration of novel membrane materials in the recovery of CO from wet industrial streams. In this work, the water vapor effect on the N, CH and CO permeability through MMMs comprised of 20 wt% hydrophilic zeolite 4A in hydrophobic PTMSP polymer were investigated in the relative humidity range 0-75%. While in the pure PTMSP membranes, the permeability of all gases decreases with water vapor activity, with almost unchanged CO/N and CO/CH selectivities, in zeolite A/PTMSP MMMs, the CO permeability increases with increasing water content in the system up to 50% R.

Water sorption in microfibrillated cellulose (MFC): The effect of temperature and pretreatment.

Water sorption behavior of two different microfibrillated cellulose (MFC) films, produced by delamination of cellulose pulp after different pretreatment methods, is examined at various temperatures (16-65°C) and up to 70% RH. The effect of drying temperature of MFC films on the water uptake is also investigated. The obtained solubility isotherms showed the typical downward curvature at moderate RH, while no upturn is observed at higher RH; the uptakes are in line with characteristic values for cellulose fibers.