Influence of silica fillers during the electron irradiation of DGEBA/TETA epoxy resins, part II: Study of the thermomechanical properties

This work describes the influence of silica fillers on the thermomechanical properties of diglycidyl ether of bisphenol A/triethylenetetramine (DGEBA/TETA) epoxy resins during ageing under electron beam irradiation. Whatever be the silica filler (pure micrometric ground and spherical silicas, nanometric silicas and coupling agent treated silicas), the glass transition temperature of the epoxy resins decreases with increasing irradiation dose, meaning that the main effect of the irradiation is chain scission. No influence of the silica fillers has been detected from the changes in the glass transition temperature with the increase in the irradiation dose. The disappearance of the cooperativity of the γ relaxation, the decrease of the α relaxation and the decrease of the elastic modulus at the rubbery plateau observed by dynamic mechanical analyses involve a decrease in the crosslink density of the epoxy resins. The occurrence of chemical reactions between the epoxy resin and the silica surface at high irradiation doses has been shown. Moreover, we show evidence that chemical reactions between the epoxy resin and the silica surface occur at high irradiation dose.     

EFFECTS OF COUPLING AGENTS ON THE CRYSTALLIZATION BEHAVIOR OF PP/T-ZnOw COMPOSITES

The objectives of this paper are to understand the crystallization behavior of polypropylene(PP)composites with surface modified tetra-needle-shaped zinc oxide whisker(T-ZnOw).T-ZnOw was surface modified with different coupling agents,such as silane coupling agents(KH-550,KH-560)and titanate coupling agent(NDZ-105),in order to improve the compatibility between PP and T-ZnOw.DSC and POM were used to characterize the melt and crystallization behavior and the crystalline structures of the composites,respectively.The results show that the surface modified T-ZnOw acts as a nucleating agent of PP crystallization,depending on the coupling agent used for modification.KH-550 and KH-560 have more apparent role in improving the interfacial interaction than NDZ-105 and induce PP crystallization at higher temperature and with smaller spherulites size.The results also suggest that the crystallization behavior depends on not only the content of coupling agent,but also the content of the surface modified T-ZnOw used in the composites.     

Thermal characteristics of polyurethane foams incorporated with phase change materials

Thermal energy storage plays an important role in heat management because of the demand for developed energy conservation, and has applications in diverse areas, from building heating/cooling systems which enable solar energy incorporation into the structure, to textiles and clothings providing an enhanced thermal comfort. In this study, we aimed to improve thermal characteristics of polyurethane rigid foams that have been widely used for thermal insulation as the ultimate energy savers due to their ability to form sandwich structures with various facer materials. Through a laboratory-scale work, two paraffin waxes acting as phase change materials, namely n-hexadecane and n-octadecane, each of which is capable of managing large heat storage/release, were directly incorporated into the polyurethane foams at different ratios. Polymerization modified by means of n-alkane addition could be achieved without any adverse effect. In order to determine both structural and thermal characteristics, seven types of foams produced were examined by FT-IR, SEM, DSC analyses, calorimeter bomb and mechanical tests. Results show that polyurethane foams can be designed as thermal insulators equipped with an improved buffering function against temperature changes.     

Vibronisches Spektralverhalten von Molekülen: XIV. Zum Einfluß der vibronischen Kopplung auf die S0-S1-Absorption und Fluoreszenz von ausgewählten 1,3-Diketonato-bor-komplexen im Rahmen der Herzberg-Teller-Näherung

Summary Based upon completely-optimized S₀ and S₁ molecular geometries the vibrational structures of S₀-S₁ absorption and fluorescence transitions of selected 1,3-diketonato boron complexes being differently substituted, are calculated within the Herzberg-Teller approach taking into account vibronic coupling contributions. In dependence on substituted diketone as well as on the co-ligand, the influence of vibronic coupling and the consequences of intensity borrowing on the spectral behaviour in absorption and fluorescence are found to be quite different for the studied boron complexes. Consequently, for some complexes their spectroscopic properties may be interpreted exclusively by means of the Herzberg-Teller approach. An analysis of the relevant vibrational modes is given.

     

Untersuchungen zur Umsetzung von [Lithium(trimethylsilyl)amido]-methyl-trimethylsilylamino-silan Me(Me3SiNLi)(Me3SiNH)SiH mit verschiedenen Elektrophilen

Investigations of the Reaction between the [Lithium(trimethylsilyl)amido]-methyl-trimethyl-silylamino-silane Me(Me₃SiNLi)(Me₃SiNH)SiH and different Electrophiles The lithium silylamide Me(Me₃SiNLi)(Me₃SiNH)SiH 1 reacts with chlorotrimethylsilan in the nonpolar solvent n-hexane to the N-substitution product Me[(Me₃Si)₂N](Me₃SiNH)SiH 2 and to the cyclodisilazane [Me(Me₃SiNH)Si—N(SiMe₃)]₂ 3 nearly in same amounts. The reaction of 1 with chlorotrimethylstannane gives besides small amounts of the cyclodisilazane 3 the N-substitution product Me[(Me₃Si)(Me₃Sn)N](Me₃SiNH)SiH 4 . By the reaction of 1 with trimethylsilyltriflate the cyclodisilazane 3 is obtained as the main product. Furthermore 2 and the cyclodisilazane 5 are formed. Ethylbromide shows no reaction with 1 under the same conditions. These results indicate the existence of an equilibrium of the lithium silylamide 1 , the silanimine Me(Me₃SiNH)Si?N(SiMe₃) and lithium hydride.     

A Novel Anti-Inflammatory d-Peptide Inhibits Disease Phenotype Progression in an ALS Mouse Model

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterised by selective neuronal death in the brain stem and spinal cord. The cause is unknown, but an increasing amount of evidence has firmly certified that neuroinflammation plays a key role in ALS pathogenesis. Neuroinflammation is a pathological hallmark of several neurodegenerative disorders and has been implicated as driver of disease progression. Here, we describe a treatment study demonstrating the therapeutic potential of a tandem version of the well-known all-d-peptide RD2 (RD2RD2) in a transgenic mouse model of ALS (SOD1*G93A). Mice were treated intraperitoneally for four weeks with RD2RD2 vs. placebo. SOD1*G93A mice were tested longitudinally during treatment in various behavioural and motor coordination tests. Brain and spinal cord samples were investigated immunohistochemically for gliosis and neurodegeneration. RD2RD2 treatment in SOD1*G93A mice resulted not only in a reduction of activated astrocytes and microglia in both the brain stem and lumbar spinal cord, but also in a rescue of neurons in the motor cortex. RD2RD2 treatment was able to slow progression of the disease phenotype, especially the motor deficits, to an extent that during the four weeks treatment duration, no significant progression was observed in any of the motor experiments. Based on the presented results, we conclude that RD2RD2 is a potential therapeutic candidate against ALS.     

Synthesis and Visible Spectral Behaviour of Some New N‐Bridgehead Heterocyclic Cyanine Dyes Incorporating Pyrazolo (4,5‐b) Indolizine (Benzoindolizine)

The new unsymmetrical N‐bridgehead, apo (zeromethine), mono‐methine, dimethine, meso substituted tetramethine and styryl cyanine dyes incorporating pyrazolo (4,5‐b) indolizine (benzoindolizine) nuclei were prepared. Structural confirmation was carried out by elemental analyses, IR, H‐NMR, mass spectra and ¹³C‐NMR with the aid of carbon DEPT spectral data. The visible absorption spectra for the newly synthesized cyanines were examined in 95% ethanol.     

Polarographic behaviour of 1,3-bis[(2-pyridyl)methyleneamino]thiourea (PMAT) in absence and presence of Triton X-100

The polarographic behaviour of 1,3-bis[(2-pyridyl)methyleneamino]thiourea (PMAT) in solutions of varyingpH has been studied both in the absence and presence of Triton X-100 (T.X-100). The mechanism for the reduction process is discussed. The adsorption effect of electrochemically inactive T.X-100 on the polarographic waves ofPMAT has been investigated. The values of the kinetic parameters for the electrode reaction at differentpH values have been computed. The applicability of the polarographic method for determination ofPMAT is also discussed.

---

Das polarographische Verhalten von 1,3-Bis[(2-pyridyl)methylenamino]-thioharnstoff (PMAT) in Anwesenheit und Abwesenheit von Triton X-100. Die polarographische Bestimmung vonPMAT

Zusammenfassung Es wurde das polarographische Verhalten vonPMAT in Lösungen mit verschiedenempH sowohl in Gegenwart als auch ohne Triton X-100 (T.X-100) untersucht. Es wird ein Mechanismus für den Reduktionsprozeß diskutiert. Der Adsorptionseffekt des elektrochemisch inaktiven T.X-100 wurde hinsichtlich der polarographischen Wellen vonPMAT untersucht. Die kinetischen Parameter der Elektrodenreaktion wurden für verschiedenepH-Werte ermittelt. Ebenso wird die Anwendbarkeit der polarographischen Methode für die Bestimmung vonPMAT diskutiert.

     

Effect of Phosphorus Content on Thermal Behaviour of Diglycidyl Ether of Bisphenol-A/phosphorus Containing Amines

Curing of diglycidyl ether of bisphenol-A (DGEBA) with phosphorus containing amide amines i.e. bis[3(3’-aminobenzamido phenyl)]methyl phosphine oxide (MB),bis[3(4’-aminobenzamido phenyl)]methyl phosphine oxide (PB), tris[3(3’-aminobenzamidophenyl)] phosphine oxide (MT) and tris[3(4’-aminobenzamido phenyl)] phosphine oxide (PT)and conventionally used curing agent 4,4’-diaminodiphenyl sulfone (D) was studied by DSC. The amines MB, PB, MT and PT were synthesised in the laboratory and were characterized by determining elemental composition, melting point, and amine equivalent. Structural characterization was done by ¹H-NMR and FTIR. The onset temperature of curing depended on the nucleophilicity of the amines and was in the orderMT≈MB<PT<PB<D. The exothermic peak temperatures were in the orderD>PB>PT>MT≈MB. The char residue of cured epoxy resin was significantly higher when phosphorus was incorporated in the cured network. Using mixed amine formulations based on amine D and P-containing amines and the molar ratio of these amines could easily control the curing characteristics. A linear relationship between char yield and P-content was observed in such formulations. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and characterization of some Cr(III), Fe(III) and Zr(IV) compounds with substituted o-hydroxy benzophenone

This work presents our data concerning the synthesis and characterization of some Cr(III), Fe(III) and Zr(IV) complexes with substituted (2-hydroxy-4-methoxy-phenyl)-phenyl-methanone - C₁₄H₁₂O₃, denoted by (L1). The synthesis of these complex compounds was performed using melted urea as reaction medium. The obtained complexes have been studied by chemical analysis, IR spectroscopy, X-ray diffraction and thermogravimetric analysis. Based on the data resulting from the thermal behaviour of the studied complex compounds, the kinetic parameters of the thermal decomposition reactions have been determined. This revised version was published online in July 2006 with corrections to the Cover Date.