Montmorillonite as a component of polysulfone nanocomposite membranes

Nanocomposite membranes containing polysulfone (PSI) and sodium montmorillonite from Wyoming (MMT) were prepared by a combination of solution dispersion and the immersion step of the wet-phase inversion method. The purpose was to study the MMT addition with contents of 0.5 and 3.0 mass% MMT in the preparation of nanocomposite membranes by means of morphology, thermal, mechanical and hydrophilic properties of nanocomposite membranes and to compare these properties to the pure PSf membrane ones. Small-angle X-ray diffraction patterns revealed the formation of intercalated clay mineral layers in the PSf matrix and TEM images also presented an exfoliated structure. A good dispersion of the clay mineral particles was detected by SEM images. Tensile tests showed that both elongation at break and tensile strength of the nanocomposites were improved in comparison to the pristine PSf. The thermal stability of the nanocomposite membranes, evaluated by onset and final temperatures of degradation, was also enhanced. The hydrophilicity of the nanocomposite membranes, determined by water contact angle measurements, was higher; therefore, the MMT addition was useful to produce more hydrophilic membranes. (C) 2009 Elsevier B.V. All rights reserved.

Anaphylactic reaction induced by a polysulfone/polyvinylpyrrolidone membrane in the 10th session of hemodialysis with the same dialyzer

The majority of severe hypersensitivity reactions in hemodialysis patients have occurred due to sensitization to ethylene oxide or to nonbiocompatible membrane dialyzers. The use of polysulfone dialyzers rarely causes hypersensitivity reactions. In the present study, we describe a case of severe life-threatening reactions induced by polysulfone dialyzers (from different manufacturers subjected to a variety of sterilization methods), which occurred after 9 sessions of hemodialysis with the same prescription, exemplifying the complexity of such reactions.

Polyethylene/(organo-montmorillonite) composites modified with ethylene/ methacrylic acid copolymer: Morphology and mechanical properties

Several composites based on high-density polyethylene (PE), organically modified montmorillonite (OMMT) and ethylene/methacrylic acid copolymer (EMAA) were prepared by melt compounding. Three Na(+)-montmorillonites (MMT) of different precedence were modified with hexadecyl trimethyl ammonium chloride in order to change their nature from hydrophilic to organophilic. The composites morphology was examined by XRD, SEM and TEM. Mechanical properties were evaluated under static conditions. A slight reinforcement was achieved only when OMMT was added to PE. When EMAA was added to the composites, it negatively interacted with OMMT, diminishing the interlayer distance of OMMT, changing the composite morphology, as if OMMT was not present in composites, and deteriorating their mechanical properties. (C) 2008 Elsevier Ltd. All rights reserved.

Resistance to degradation of resin-modified glass-ionomer cements dentine bonds

Objective: To evaluate the effect of EDTA pre-treatment of dentine on resistance to degradation of the bond between dentine and resin-modified glass-ionomer cements. Methods: Sixty non-carious human molars underwent cavity preparations. Teeth were restored with Fuji II LC or Vitremer. Half of the cavities were restored following manufacturers` instructions whereas the other half was pre-treated with EDTA (0.1 M, pH 7.4) for 60 s. Teeth were stored in water at 37 degrees C for 24 h, 3 months or submitted to 10% NaOCl immersion for 5 h. Teeth were sectioned into beams (1 +/- 0.1 mm) and tested to failure in tension at 0.5 mm/min. Bond strength data (MPa) were analyzed by ANOVA and SNK multiple-comparisons tests (p < 0.05). Results: When EDTA was used for pre-treatment of dentine, higher bond strengths were observed for both cements. Degradation challenges produced a decrease in bond strength values only in the Vitremer group. This decrease was avoided when EDTA was used for dentine treatment before restoring with Vitremer. Conclusions: EDTA pre-treatment of dentine increases bond strength of resin modified glass-ionomers cements to dentine and improves resistance to degradation of the bond between Vitremer and dentine. (C) 2009 Elsevier Ltd. All rights reserved.