Papers by Keyword: Oxygen Permeability

Abstract: The ability to plasticize Hydroxypropyl Methyl Cellulose/Beeswax (HPMC/BW) composites depends on plasticizers and their concentration. This paper conducted studying on the impacts of plasticizers to HPMC/BW properties. The plasticizers were used in this research included Glycerol (G), Propylene Glycol (PG), and Polyethylene Glycol 400 (PEG 400) which had the concentration changed in range of 1-3%. HPMC/BW composite films incorporated with 2% of plasticizers formed films with the best characteristics among three tested concentration. Tensile strength and elastic modulus of films were decreased when adding plasticizers, whereas elongation at break were increased. Therefore, it caused an increase in oxygen permeability of HPMC/BW films in comparison with the control film. However, Glycerol showed the lowest Oxygen Permeability (OP) values compared to other composite films. The films were evaluated its microstructural quality using method of scanning electron microscopy (SEM) which had the effects of plasticizers and their efficiencies of plasticizing polymer networks.

Abstract: This paper draws on a roll coating method which used for the production of coated paper. Polylactide coating cardboard was prepared through the solvent coating, and study its packaging performance. In this study, chloroform is based solvent, ethanol or n-propanol as auxiliary solvents, poly (ethylene glycol) or poly caprolactone as plasticizer, and the water vapor permeability, oxygen permeability and heat sealability of polylactic acid coated cardboard.

Abstract: This paper is concerned with the preparation of cellulose packaging films with high oxygen permeability. The films were prepared from cotton pulp and wood pulp by the cast-wiped method using N-methymorpholine-N-oxide (NMMO) as a solvent. The effects of processing parameters on the structure and performance of cellulose films were also studied. The results show that for optimum processing of the films cotton pulp was the preferred raw material, the optimum pulp concentration in the casting solution was 5%, and the optimum temperature for the coagulation bath was 40°C. Using the above process conditions resulted in packaging films with high oxygen permeability making them suitable for use in packaging fruits and vegetables.

Abstract: The formation of protective Cr₂O₃ scale at high temperature was evaluated using Wagner’s theory of binary alloy oxidation. The results show that at 1073 K, around 9.8 wt% of Cr is required to form external Cr₂O₃ scale, and 3.5wt% of Cr is needed to maintain the scale. Introduction of water vapor has shifted the critical Cr concentration to higher value. The effects of water vapor in increasing Cr critical concentration to form external Cr₂O₃ scale was disscussed from view of oxygen permeablility and Cr diffusivity in the alloy. It is concluded that Cr diffusivity has negligible effect, while oxygen permeability increase with the presence of water vapor, thus increase the oxidation rate.

Abstract: The boundary constants between internal and external oxidation of Si or Cr containing steels (Fe-Si alloys or Fe-Cr alloys) at 850°C were calculated in order to clarify the formation mechanism of fayalite scale (Fe₂SiO₄) or chromite scale (FeCr₂O₄), which can form as a “sub-scale” in Si or Cr containing steels. The diffusion coefficient of oxygen in the alloy, Do, and the oxygen concentration at the specimen surface, N_O^(s), which are constituents of the internal oxidation rate constant, (2D_ON_O^(s)/N_B^(O)n), were calculated for various oxidation conditions, and the rate equation for internal oxidation was derived. By comparing the calculated and measured values of (2D_ON_O^(s)/N_B^(O)n), we confirmed that the rate equation determined for internal oxidation was reasonable. The boundary condition between internal and external oxidation of Si or Cr containing steels (Fe-Si alloys or Fe-Cr alloys) at 850°C were also calculated by substituting the calculated values of D_O and N_O^(s) into the rate equation.

Abstract: Polymer-reinforced polymer composites have been successfully created from blends of engineering and commodity plastics. These microfibril reinforced composites (MFCs) contain molecularly oriented in-situ fibrils, evenly dispersed throughout a homogeneous matrix. MFCs have several potential applications in a range of areas including food packaging materials and biomedical scaffolds. This paper provides an overview of the characterisation of several MFCs derived from polyethylene/poly(ethylene terephthalate) (PE/PET) blends. It investigates the tensile properties of MFCs with different microfibril orientations as a result of various consolidation techniques. It also describes a study on the oxygen permeability of moulded MFC films and evidence of biological cell growth on microfibrillar polymer structures.

Abstract: The objective of this study was to manufacture and investigate the properties of barrier films made from microfibril-reinforced polymer composites (MFCs) based on blends of linear low density polyethylene (PE) and poly(ethylene terephthalate) (PET). Blends containing 30 wt% of PET were prepared and extruded into strands. These were then subjected to cold drawing and compression moulded into thin films. The permeability of the films to oxygen gas was measured using a permeation test chamber and the effect of the draw ratio on the size of the reinforcing fibrils was also observed. Scanning electron microscope (SEM) revealed substantial differences in the structures of neat and MFC films. A model developed for predicting the permeability of filled polymer composite films was modified and compared to the test results. The draw ratios of the MFCs did not appear to have a significant effect on oxygen permeation, despite altering the dimensions of the reinforcing fibrils. The MFC films were found to be half as permeable as the neat polymer films.

Abstract: The structure, microstructure, electric transport and oxygen permeation properties of (La,Sr)(Ga,Mg,Fe)O3-δ ceramics with perovskite or brownmillerite structures have been studied. Oxygen permeability values of ~0.1 cm3/cm2·min has been revealed at 1000 K for the ceramics studied. The correlation of electroconducting properties of the LaGaO3-based ceramics with perovskite and brownmillerite structures to their oxygen permeability characteristics has been proved.

Abstract: Due to relatively high oxygen permeability, lanthanum-strontium ferrite phases are of interest as ceramic membrane materials for the partial oxidation of natural gas. This work was focused on the study of perovskite-type ferrites co-doped with Sr2+ and Ce4+ or Nb5+, with particular emphasis on the ionic transport and thermodynamic stability limits at low oxygen chemical potentials. Dense membranes of La0.5-2xCexSr0.5+xFeO3-δ (x = 0 - 0.2) and La0.5-2ySr0.5+2yFe1-yNbyO3-δ (y = 0 - 0.1) were characterized employing X-ray diffraction (XRD), scanning electron microscopy (SEM), dilatometry, oxygen permeation and faradaic efficiency studies, and the measurements of total conductivity and Seebeck coefficient in the oxygen partial pressure range from 10-20 to 0.5 atm. The incorporation of Ce4+ or Nb5+ was found to decrease thermal expansion and electronic transport parameters, whereas the ionic conductivity behavior is complex, indicating the relevance of redox interactions of the variable-valence cations and the concentration of mobile oxygen vacancies.