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Barrier Materials (barrier + material)
Selected AbstractsCrosslinked Bicontinuous Cubic Lyotropic Liquid-Crystal/Butyl-Rubber Composites: Highly Selective, Breathable Barrier Materials for Chemical Agent Protection,ADVANCED MATERIALS, Issue 24 2006X. Lu A breathable material that can act as a barrier to chemical agents is presented. The material is composed of butyl rubber and a crosslinkable lyotropic liquid crystal. Under the right synthesis conditions, a cubic phase with the desired selectivity properties results (see figure). The material is highly permeable to water vapor, but strongly impermeable to a mustard gas simulant. Application of the material for effective personal protection against such chemical agents is envisaged. [source] Polymer-assisted regeneration therapy with Atrisorb® barriers in human periodontal intrabony defectsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 1 2004Lein-Tuan Hou Abstract Aim: This study compared clinical results of 40 periodontal osseous defects treated by two types of absorbable barrier materials. Material and Methods: Thirty patients (23 males and seven females) suffering from moderate to advanced periodontitis (with comparable osseous defects) were randomly assigned to receive either Atrisorb® barrier (n=22; group A) or Resolut XT® barrier (n=18; group B) therapy. Periodontal phase I treatment and oral hygiene instruction were performed before periodontal surgery. Papillary preservation, partial thickness flap, citric acid root conditioning, and decortication procedures were applied during the operation. Bone defects were filled with demineralized freeze-dried bone allograft and minocycline mixture (4:1 ratio). Postoperative care included 0.10% chlorhexidine rinse daily and antibiotic medication for 2 weeks. Clinical assessments including probing depth (PD), clinical attachment level (CAL), gingival recession (GR), plaque index (PlI), gingival index (GI), and radiographic examinations were taken at the baseline, preoperatively and at 3 and 6 months after regenerative surgery. Results: Six months following therapy, both Atrisorb® and Resolut XT® groups had achieved comparable clinical improvement in pocket reduction (3.9 versus 4.4 mm), attachment tissue gain (clinical attachment gain; 3.5 versus 3.6 mm), and reduction in the GI and in the PlI. Within-group comparisons showed significant attachment gain and pocket reduction between baseline data and those at both 3 and 6 months postoperatively (p<0.01). There were no statistically significant differences in any measured data between groups A and B. Conclusions: The results of this study indicate that a comparable and favorable regeneration of periodontal defects can be achieved with both Atrisorb® and Resolut XT® barriers. Further long-term study and histologic observations of tissue healing are needed to evaluate whether Atrisorb® is promising for clinical use. [source] A simple model for the interaction between water vapour and oxygen transmission in multilayer barrier materials intended for food packaging applicationsPACKAGING TECHNOLOGY AND SCIENCE, Issue 4 2008Marianne Jakobsen Abstract The low oxygen permeability of the ethylene-vinyl alcohol copolymer, EVOH, is outstanding, but is also known to be very sensitive to moisture uptake and cannot be used as a monolayer packaging material. In this paper, theory is presented in order to calculate the average water activity of the EVOH layer at steady state and the corresponding oxygen barrier for different multilayer structures using various polymer types and layer thicknesses. Multilayer materials can be designed for different food packaging applications and storage conditions, in order to keep the relative humidity of the barrier below recommended 75%, by varying the thickness of the outside versus the inside protective layers and/or varying the water vapour transmission rate of the outside versus the inside layer. The conclusion reached is that to retain the optimal barrier properties and thereby the optimal protection of the food, asymmetric multilayer structures are necessary. Copyright ©2007 John Wiley & Sons, Ltd. [source] Interface phonons and polaron effect in II-VI quantum wellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2010Alexander Yu. Abstract The theory of large radius polaron in II-VI quantum wells is developed. The analytic expressions for polaron binding energy are obtained for the electron, the hole and the exciton polarons. The numerical results obtained show that the strong electron-phonon interaction conditions can be realized in the quantum wells based on a number of II-VI compounds. The influence of the interface optical phonons on the polaron states is accounted for. The extent of interface phonon influence depends on the properties both of the quantum well and of the barrier materials. It is shown that the interaction of charge particles with the interface phonons can lead to the enhancement as well as to the reduction of the polaron effects. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] InAsSb/InGaAs quantum nanostructures on InP (100) substrate: observation of 2.35 µm photoluminescencePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2006F. Doré Abstract A theoretical and experimental study of the electronic properties of InAsSb quantum dots (QDs) grown on InP substrate is presented. Unstrained bulk InAsSb presents a direct gap between 0.1 eV to 0.35 eV, suitable for mid infrared emitters (3,5 µm). However, strain and quantum confinement effects may limit the extension of the emission spectrum of these nanostructures towards longer wavelengths. Various combinations of barrier materials are considered in the simulations. First photoluminescence spectroscopy experiments on molecular beam epitaxy (MBE) grown samples show promising results. Triple stacks of InAs QDs embedded in a GaInAsP alloy lattice matched to InP and grown by the Stranski-Krastanov mode exhibit room temperature (RT) luminescence at about 2 µm. Emission wavelengths as long as 2.35 µm have been observed at RT in a InAsSb/InGaAs/InP structure. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Compatibilized poly(ether imide)/LCP blends: drawing ability and mechanical properties of the ribbonsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 7 2002F. J. Vallejo Abstract The effects of the addition of polyarylate (PAr) on the drawing ability of poly(ether imide) (PEI)/Rodrun liquid-crystalline 5000 (Ro LC5000) (Ro) blends and on the mechanical properties of their ribbons were studied. The compatibilizing effect of the PAr led to an increase in the drawing ability of the blends, as seen by the fact that the maximum Ro content compatible with the drawing process increased from 15 to 30%. This may lead to new applications in the field of gas barrier materials. The presence of PAr also led to an increase in the adhesion between the two phases of the blends and consequent improved ductility. However, the very high modulus of elasticity and tensile strength in the direction of orientation (up to three-fold those of the matrix) due to the less developed fibrillation were smaller than the corresponding values before compatibilization. These very large modulus of elasticity and tensile strength values and those perpendicular to the direction of orientation, which were similar to those of the matrix, led to a high anisotropy in the extruded ribbons that increased with the draw ratio (DR) and the Ro contents. The high mechanical properties of the ribbons may be used and the anisotropy diminished by layering the ribbons in, and perpendicular to, the direction of orientation, according to the expected external load. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||