No abstract

The influence of different organobentonites on the decomposition and the combustion behaviour of an epoxy resin were examined. The epoxy resin is a cationically polymerised cycloaliphatic epoxy resin flexibilised with poly(tetrahydrofuran) (PTHF), with hydroxyl endgroups. The bentonite was modified with either an ammonium or a phosphonium salt. The thermal decomposition of the PTHF induced by the initiator, used for the cationic polymerisation, did neither take place for the nanocomposite based on the ammonium bentonite nor for that based on the phosphonium bentonite. This improved decomposition characteristic lead to a larger time to ignition for both kinds of nanocomposites compared to the not modified polymer, which is not the case for other polymer/clay nanocomposites described in the literature. The fire behaviour was investigated using limiting oxygen index (LOI), a horizontal burner test and a cone calorimeter. The forced flaming conditions in the cone calorimeter were varied using different external heat fluxes between 30 and 70 kW · m−2. The fire behaviour of the nanocomposites was improved in comparison to the polymer, and phosphonium bentonite was superior to ammonium bentonite. The main mechanism is a barrier formation resulting in a reduction of the fire growth rate, which was more pronounced in the case of high external heat fluxes. magnified image

The study of the influence of the crystal morphology of laser dye-loaded AlPO 4 -5 molecular sieve on the previously reported laser properties, i.e., laser threshold power density, modes of laser emission and lightfastness, requires synthesis procedures resulting in single crystals of varied length-per-width ratios. The suppression of undesired side-phases (AlPO 4 -8, VPI-5), as well as the temperature-time field, for the production of pure Rhodamine BE50-loaded crystals with desired uniform morphology by the microwave-heated crystallization method are evaluated and discussed. Uniform plate-like crystals with a thickness of less than 4 mm, for which favorable laser properties can be expected, are obtained only in a small temperature window 150¡5 uC with reaction times of about 10 minutes.

009ChemInform Abstract The title mineral (from the former mine "Gruene Aue", Siegerland) crystallizes in the orthorhombic system, space group P212121, Z=4. In its structure, a new type of ABCX3 compound, the Bi atom and its three nearest S atoms form a trigonal pyramid. The polyhedron, which results from consideration of a fourth S atom at a greater distance, is very similar to the TeO4 polyhedron in Zn2Te3O8. Cu and Ni can either occupy the M(1) position (tetrahedrally coordinated by S) or the M(2) position (coordinated by four S in the quadratic base and two Bi at the vertices of a tetragonal bipyramid). Crystal chemical considerations show the M(1) and M(2) positions to be occupied by Cu and Ni, respectively.

No abstract