Enhancing the CO2 Separation Performance of Matrimid 5218 Membranes for CO2/CH4 Binary Mixtures

The effect of CO₂‐philic additive polyethylene glycol (PEG) 200 in Matrimid 5218 on the separation performance of prepared membranes was evaluated in a binary gas mixture. Matrimid/PEG 200 flat‐sheet blended membranes with low PEG concentrations were prepared by the dense film‐casting method. Pure Matrimid and blended membranes were characterized by FTIR spectroscopy, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and permeation measurements. The addition of 4–5 % of PEG enhanced considerably the CO₂ permeability of the Matrimid matrix. The best formulation, Matrimid/PEG 200 (96/4), showed in comparison to pure Matrimid a more than threefold increase in CO₂ permeability and an increase in separation factor of about 40 %.     

Setting behavior and bioactivity assessment of calcium carbonate cements

Calcium carbonate cements have emerged in the last few years as an attractive candidate for biomedical applications. They can be easily prepared by mixing water with two metastable calcium carbonate phases––amorphous calcium carbonate (ACC) and vaterite––which (re)crystallize into calcite during setting reaction. The transformation kinetics (and therefore the final surface cement composition) strongly depends on the initial mixture design and is controlled by the dissolution of ACC, whereas calcite nucleation typically controls their recrystallization in fluid batch experiments. Novel compositions are presented in this paper by incorporating organic molecules as a proxy to test their capability to carry on other biomolecules like proteins or antibiotics. The hardened samples are microporous and show excellent bioactivity rates, although their mechanical properties still remain poor. However, this would not be a handicap for in-vivo applications such as bone filling, especially in low mechanical stress locations.     

Characterization of the mass transfer of lyophilized products based on X-ray micro-computed tomography images

ABSTRACT

This paper proposes a systematic work process for the rapid determination of resistance to vapor flow given by the products being freeze-dried. This approach couples mathematical modeling and 3D nondestructive X-ray imaging to reconstruct the internal structure of lyophilized samples. Knowledge of the internal structure is fundamental to better understand the relationship between freezing and within-product heterogeneity as well as between freezing and the drying behavior of the product being lyophilized. The method was validated upon mannitol-based formulations using various freezing protocols. This stepwise approach was demonstrated to be helpful to lyophilization professionals for the control of within-product heterogeneity and for the optimization of the cycle.     

Piedmont olive oils: Compositional characterization and discrimination from oils from other regions

Piedmont olive oils collected in 2010 were characterized, for the first time, in terms of their fatty acid profile using GC and ¹H NMR and compared to other oils from five Italian regions. Applying NMR spectroscopy on the olive oil samples, without manipulation, it is possible to calculate the proportion of the different acyl groups in the oil samples. As the area of the signals is proportional to the number of each type of proton in the sample, saturated, monounsaturated (oleic acid) and polyunsaturated (linoleic and linolenic acids) fatty acids were determined. All analyzed samples can be categorized as virgin olive oil extra quality according to the oleic/linoleic ratio. Based on a preliminary geographical investigation, olive oils produced in the North of Italy show a good separation from those from Central and Southern regions. Practical applications : Oil characterization of new products is the basis for further nutritional and food technological investigations and the quality of edible oils is of great concern especially for products available on the market. The two adopted techniques show a remarkable agreement in the evaluation of fatty acid composition of oil samples. Also, this research, by means of ¹H NMR, provides information on geographical origin of the olive oils of Northern Italian regions with respect to Central and Southern regions.     

Kinetics of the hydrogenation of NBR by hydrazine and oxygen,using selenium as a catalyst

The kinetics of hydrogenation of the acrylonitrile‐polybutadiene (NBR) rubber by the action of hydrazine in the presence of selenium and oxygen was studied by varying reaction parameters such as latex and catalyst concentrations. The method of initial rates gives a reaction order of 0.91 and a rate constant of 3.2 × 10¹ L mol^?1 h^?1 in relation to the NBR latex concentration, and an order of 0.86 and a rate constant of 3.3 × 10¹ L mol^?1 h^?1 in relation to the catalyst concentration. Based on these values, a first‐order mechanism with the formation of a diimide intermediate is suggested, which is formed through the oxidation of hydrazine in an oxygen atmosphere in the presence of selenium catalyst. This diimine species reacts rapidly, reducing the carbon–carbon double bonds of NBR resulting in the formation of HNBR rubber. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Luminescent polydibenzothiophene thin film obtained by glow discharge method

This work presents the synthesis by plasma and characterization of luminescent polymer thin films of dibenzothiophene (DBT) by plasma polymerization. The DBT is solid at room conditions and was sublimated and introduced to the plasma reactor to produce the chemical reactions with the vapors. The results indicated the production of polymers with benzene and thiophene rings in the structure as well as methylene groups. The polymer structure was studied by Fourier transform infrared spectroscopy and ¹³C‐CPMAS. The thermal analysis showed a residual mass of 60% at 800°C, which suggests a great thermal resilience in the polymer. The critical superficial tension was calculated with a Zisman plot and was 25 mN/m. The polymer has a fluorescent green emission between 400 and 660 nm and an orange emission between 660 and 850 nm. This effect can be a consequence of the electronic distribution along the structure in aliphatic and aromatic segments with benzene and thiophene rings. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Evaluation of the adsorption behavior of freeze-dried passion fruit pulp with added carriers by traditional biospeckle laser techniques

This work was aimed to evaluate the potential of the biospeckle laser technique to monitor the sorption behavior of freeze-dried passion fruit pulp. For this purpose, passion fruit pulp with carriers (sucrose, fructose, maltodextrin, and ethanol) was added at different concentrations and combinations were freeze dried, and their sorption behavior was monitored in environments with relative humidities of 0.113, 0.529, 0.753, and 0.903 by gravimetric and biospeckle laser analyses. The thermal and structural stabilities of the powders were evaluated using differential scanning calorimetry and scanning electron microscopy. The biospeckle laser tool was capable of monitoring the water activity present in the passion fruit powders at relative humidities of 0.113, 0.529, and 0.753. In a relative humidity of 0.113, adsorption was slow, and the speckle pattern was altered regardless of the added carrier. Relative humidities of 0.529 and 0.753 resulted in an adsorption behavior and altered speckle pattern, which were variable, i.e., they were dependent upon the added carriers. At a relative humidity of 0.903, the adsorbed mass of water and alterations in the speckle pattern over time were intense. Ethanol furthered the degree of organization of the structures in the crystallization process. Maltodextrin was effective at stabilizing the passion fruit powders, resulting in poorer water adsorption and increased vitreous transition temperature. Fructose promoted typically amorphous freeze-dried powders, due to the high glass transition temperature and the formation of highly sticky tubular and roundish structure.     

Vickers Crack Nucleation of Glass Sheets Coated by Thin Silica Gel Layers

SiO₂ gel layers of different thickness have been deposited on glass sheets by dipping from gelling solutions with different concentrations of silicon alkoxide. Some mechanical properties of the coated samples such as hardness (H), elastic modulus (E), crack formation tendency, and tensile stress in the film (σ) have been measured by microindentation techniques and slide deflection. SiO₂ films deposited from more dilute solutions had lower H, E, and σ values, accounting for the observed higher resistance to crack nucleation in comparison with that found for samples prepared from more concentrated solutions.