Thermoxidative Decomposition of Some Polysulfones under Dynamic Conditions of Heating

Kinetic aspects of the first step of thermoxidative decomposition, under dynamic conditions of heating, of some polysulfones have been studied. The dependence of the kinetic parameters on the heating rate and conversion degree has been established. The compensation effect and conversion function have also been discussed. Polysulfone decomposes by the breaking of the main chain, a process involving very high activation energy. Chemically modified polysulfones show the first step of thermoxidative decomposition at relatively low temperatures. This step corresponds to the elimination of functional side - groups for the bromomethylated polysulfone while in the case of the carboxylated polysolfone, the loss of the carboxyl group is probably accompanied by a crosslinking reaction. This revised version was published online in July 2006 with corrections to the Cover Date.     

On the compatibility of binary and ternary random copolymers of acrylonitrile with vinyl acetate and/or α-methylstyrene—II: The influence of the time factor

The time dependence of the microscopical aspect, crystallinity, viscosity of the spinning solutions and the thermal and tinctorial properties of films formed from binary, ternary copolymers and binary copolymer mixtures of acrylonitrile with vinyl acetate and χ-methylstyrene have been compared. The characteristics of binary copolymers and incompatible mixtures are stable with time, while those of ternary copolymers and pseudocompatible mixtures evolve towards a limiting state. with phase separation.     

Side chain thermotropic liquid crystalline polysulfone obtained from polysulfone udel by chemical modification

Polysulfone udel was chemically functionalized with chloromethylene functional groups via the chloromethylation reaction. A new azomethine dimesogen containing one phenolic hydroxyl functional group was recently synthesized and proved to exhibit a large nematic mesophase range in the liquid state. Further reaction of the dimesogen with the functionalized polysulfone using a transquaternization reaction led to new polysulfones bearing pendant rigid dimesogenic units--no spacer being involved in the chemical design of the polymer. The polymers were characterized by IR, ¹H NMR spectroscopy techniques, and their thermotropic liquid crystallinity behaviour was studied by optical polarizing microscopy (PLM) and DSC measurements. Enantiotropic nematic mesophases were observed under the PLM. A dependence of the melting temperature on the degree of substitution was noticed.     

A remark concerning Putinar’S model of hyponormal weighted shifts

The question whether a hyponormal weighted shift with trace class self-commutator is the compression modulo the Hilbert-Schmidt class of a normal operator, remains open. It is natural to ask whether Putinar’s construction through which he proved that hyponormal operators are subscalar operators provides the answer to the above question. We show that the normal extension provided by Putinar’s theory does not lead to the extension that would provide a positive answer to the question.     

Positive solutions for nonlinear periodic problems

We consider a nonlinear periodic problem driven by the scalar p-Laplacian and with a nonsmooth potential. Using the degree map for multivalued perturbations of (S)₊-operators and the spectrum of a weighted eigenvalue problem for the scalar periodic p-Laplacian, we prove the existence of a strictly positive solution. Michael E. Filippakis: Researcher supported by a grant of the National Scholarship Foundation of Greece (I.K.Y.)     

Hypercoordinated diorganoantimony(III) compounds of types [2-(Me2NCH2)C6H4]2SbL and [PhCH2N(CH2C6H4)2]SbL (L = Cl,ONO2, OSO2CF3). Synthesis,structure and catalytic behaviour in the Henry reaction

The compounds [2-(Me₂NCH₂)C₆H₄]₂SbL (L = ONO₂ ( 2 ), OSO₂CF₃ ( 3 )) and [PhCH₂N(CH₂C₆H₄)₂]SbL (L = ONO₂ ( 5 ), OSO₂CF₃ ( 6 )) were prepared by reacting [2-(Me₂NCH₂)C₆H₄]₂SbCl ( 1 ) and [PhCH₂N(CH₂C₆H₄)₂]SbCl ( 4 ), respectively, with the appropriate silver(I) salt in a 1:1 molar ratio. The new species 2 – 6 were structurally characterized in solution using multinuclear NMR and in the solid state using infrared spectroscopy. The solid-state structures for compounds 2 , 4 and 6, as well as for the hydrolysis ionic product [{2-(Me₂N⁺HCH₂)C₆H₄}{2-(Me₂NCH₂)C₆H₄}SbOH][CF₃SO₃]⁻ ( 3h ) were determined using single-crystal X-ray diffraction. Medium to strong intramolecular N→ Sb interactions were observed in all these four compounds, thus resulting in hypercoordinated organoantimony(III) species 14-Sb-6 in 2 and 10-Sb-4 in the cation of 3h and in 4 and 6 . Compounds 1 – 6 and the starting amines PhCH₂NMe₂ and PhCH₂N(CH₂C₆H₄Br-2)₂ were investigated as catalysts in the Henry (nitroaldol) addition of nitromethane to benzaldehyde. The activity of compounds 1 – 6 resulted as an effect of the cooperation of the positively charged antimony with the negatively charged nitrogen.     

Heat affected zones in polymer laser marking

Laser marking is based on the laser heating of the subjected material, the heating being below the melting temperature or thermal degradation starting point. Within and nearby the mark, the material is chemically, physically and mechanically affected. This means that the main characteristics are changing in such a way that the material is ageing. Thermal and mechanical analysis can be used to determine the modification of the material, which is important and necessary to know for predicting its use lifetime. This paper investigates the physical and mechanical modification of the polymer HDPE100, when laser marking is applied. Burst stress, elongation and relaxation modulus were determined for the base material, within the heat affected zone and within the laser burned mark. Information on the crystallization rate and on the elongation viscosity is also reported. According to the results, the polyethylene has very fast crystallization and that affects the marking process if lower than appropriate maintaining during heating process is applied. It becomes stabile after 0.23 min, when it is tested at 103 °C. The elongation viscosity was analysed and values of 10⁵ Pa s were recorded for 10 s, which is a usual time of applying pressure. The performed analysis revealed about 10 % difference between the relaxation modulus of the irradiated and non-irradiated HDPE.     

An effective analytical approach to nonlinear free vibration of elastically actuated microtubes

Meccanica - Based on Hamiltonian principle and a modified couple stress theory, a nonlinear differential equation of motion of electrostatically actuated microbeams is presented. The method of...     

Interaction of L-Ascorbic Acid with Activated Carbon: Kinetic Studies and the Effect of pH

Colloid Journal - This article investigates the interaction of vitamin C with commercial activated Granucol-type carbons and newly produced AC-C coal at 25 and 35°C. L-Ascorbic acid molecules...