Permeation and Sorption of Water and Gases Through EVA Copolymers Films

The transport of water and gases (pure oxygen and carbon dioxide) through poly(ethylene-co-vinyl acetate) (EVA) films of different VA contents and through a low density polyethylene LDPE (used as reference with 0 wt.% VA), was analysed by permeation and sorption measurements. In the case of water, for EVA of 70 wt.% VA, a plasticization effect on the material was observed. For EVA of 19 wt.% VA, there was no plasticization, while for EVA of 4.5 wt.% VA and for LDPE, the water diffusion coefficient decreases with increasing water. An empirical law was then found to account for the reduction of the water diffusivity. A negative plasticization effect was attributed to the formation of water clusters in these rather non polar polymers. This latter result was confirmed by sorption measurements and infra-red spectroscopy. The increase in water sorption extent with the VA content leads to a steady increase in the water permeability in the EVA copolymers. In the case of gas permeation, both for O₂ and CO₂ and whatever the VA content of the copolymer used, the experimental curves are characterized by a constant diffusion coefficient. This is confirmed by sorption experiments. In terms of gas permeability, EVA copolymers are characterized by low coefficients especially for oxygen. In the EVA rubbery copolymers, The O₂ solubility coefficient does not increase with the VA content due to the lack of polar interactions, while the CO₂ one increases due to the overall interactions between CO₂ induced dipoles and the polar the VA carbonyl groups. For these copolymers, the H₂O/CO₂ and H₂O/O₂ selectivities are very high. The experimental values of the selectivities indicate that these EVA copolymers appear as good candidates for applications using high perm-selectivity properties. Electronic Publication     

Abstracts of invited papers

Abstracts of invited papers     

Characterization of interphases appearing on LiNi0.5Mn0.5O2 using Li MAS NMR

⁷Li MAS NMR, usually a bulk characterization technique, is used here to analyze the positive electrode/electrolyte interphase. The sharpening of the NMR spectra line shape as the amount of surface species increases shows that the observed signal is clearly the sum of signals due to the distribution of lithium ions in the interphase in terms of distance from the bulk of electrode active material. This technique is then used to compare characteristics of the interphase coming from the contact with LiPF₆-based electrolyte in the case of storage or electrochemical cycling. A clear influence of the change of potential on the interphase configuration and in particular on its intimacy with the bulk of active material is deduced from the change in NMR spectra lineshape. This information is hardly obtained by other characterization technique, making NMR a powerful tool for the study of interphases and passivation layers in lithium batteries materials.     

Preparation from bovine colostrum of a fraction rich in latent transforming growth factor-β2 and cleared of most allergenic proteins by one-step Cibacron Blue chromatography

A strategy was developed for the preparation of a latent transforming growth factor-β2 (latent TGF-β2) rich fraction from bovine colostrum. Different conventional chromatography techniques were tested to investigate some physicochemical properties of latent TGF-β2 complexes to optimize their recovery. Three latent TGF-β2 forms were detected by gel filtration (600, 150–250 and 65–150 kDa). Cation exchange chromatography showed that the pI of latent TGF-β2 was above pH 7; hydrophobic interaction chromatography showed that the hydrophobicity of latent TGF-β2 was much higher than that of other whey proteins. Affinity chromatography on Cibacron Blue 3G was used to separate latent TGF-β2 and immunoglobulin G from the most immunogenic proteins, α-lactalbumin, β-lactoglobulin and albumin. Optimum conditions were determined: preparation of a fraction 26 times richer in TGF-β2 than in serocolostrum was obtained with a good yield (up to 70%) of TGF-β2, 80% of which was in the latent form.     

Processing of reaction-bonded B4C–SiC composites in a single-mode microwave cavity

In this study, the reaction sintering of boron carbide, which consists in doing reactive infiltration of molten silicon throughout a porous sample made of B₄C and carbon graphite was investigated. Thus, it has been shown that a single-mode microwave cavity can be successfully used to produce reaction-bonded B₄C–SiC composite. A specific package, consisting of a SiC based susceptor and a boron nitride based insulating container, was used to heat up the B₄C–Si system using a single-mode microwaves cavity under an Ar–H₂ atmosphere. Pore-free B₄C–SiC composite successfully produced consists of a mixture of B₄C and polygonal shaped β-SiC within a residual silicon matrix. The indentation technique permits to determine mechanical properties of the samples which are compared to those obtained conventionally. It appears that the average hardness (H≈22 GPa) value is quite constant all along the sample thickness which highlights good homogeneity of the samples obtained. Some aspects of the microstructure are also discussed and compared to those of samples conventionally obtained.     

Cultural and generational influences on privacy concerns: a qualitative study in seven European countries

This research examines how European citizens decide to disclose and protect their personal data and thereby reveals cultural and generational divides. Focus group discussions featured either young people, aged 15 to 24 years, or adults, between 25 and 70 years of age, and were conducted in seven EU member states. The results of a computer-aided text analysis with two complementary software packages suggest similarities and differences in participants’ views and privacy concerns (PC). Responsibility is relevant to personal data management, which represents a hotly contested issue. A geographical north–south divide appears for the importance of responsibility as opposed to trust. Moreover, people regard disclosure differently in the south (as a choice) and east (as forced) of Europe. Younger people express more positive attitudes toward data management, feel more responsible, and are more confident in their ability to prevent possible data misuse. Their lower PC and greater protective behaviours (i.e., a potential reversed privacy paradox) may help explain contradictory results in prior literature. These results offer significant and useful theoretical, managerial, and policy implications.     

Hydrate phase equilibria for hydrogen+water and hydrogen+tetrahydrofuran+water systems: Predictions of dissociation conditions using an artificial neural network algorithm

In this communication, a mathematical model based on feed-forward artificial neural network algorithm is presented, which can estimate hydrate dissociation conditions for the hydrogen+water and hydrogen+tetrahydrofuran+water systems. To develop this algorithm, the experimental data for the hydrate dissociation conditions of the latter two systems with different concentrations of tetrahydrofuran in aqueous phase below its stoichiometric concentration (i.e., ?0.059) have been used. Independent experimental data (not used in training and developing this algorithm) have been employed to examine the reliability of this method. It is shown the agreement between the predictions and the experimental data is acceptable demonstrating the reliability of this algorithm as a predictive tool.