Effect of different dispersing agents in the non-isothermal kinetics and thermomechanical behavior of PET/TiO2 composites

This work is based on the analysis of the influence of dispersing agents on the non-isothermal kinetics, thermomechanical behavior and dispersing action of PET/TiO₂ nanocomposites. The influence of two montanic waxes and an amide wax used as dispersing agents in the nucleating effect of the nanoparticles is studied. The dispersing agents are the following: a) a partly saponified ester of montanic acids (PSEMA), b) an ester of montanic acids with multifunctional alcohols (MAWMA) and c) an amide wax based on N,N′-Bisstearoyl ethylenediamine (AW). The non-isothermal kinetics based on the Avrami method revealed that MAWMA and PSEMA favors the nucleating effect of the nanoparticles when are included in PET. Birefringence microscopy points out the good dispersing capacity of MAWMA and AW and the termomechanical analysis confirmed that the ester of montanic acids with multifunctional alcohols MAWMA shows the best dispersing properties and best promotes the nucleating effect of the TiO₂ nanoparticles when used for PET/TiO₂ nanocomposites production.     

Asymptotic equivalence of discretely observed diffusion processes and their Euler scheme: small variance case

This paper establishes the global asymptotic equivalence, in the sense of the Le Cam \(\Delta \)-distance, between scalar diffusion models with unknown drift function and small variance on the one side, and nonparametric autoregressive models on the other side. The time horizon \(T\) is kept fixed and both the cases of discrete and continuous observation of the path are treated. We allow non constant diffusion coefficient, bounded but possibly tending to zero. The asymptotic equivalences are established by constructing explicit equivalence mappings.     

Ion exchange in dimethyl sulfoxide media. IV

Summary Selective separations of beryllium from other metal ions (Cu, Cd, Zn, Ni, Fe, Co, Mg, Ca, Sr, Ba, Al, and Pb) were achieved by means of cation exchange in an aqueous 20% v/v DMSO medium containing 0.25 mol/l of thiocyanate. The observed improvements of separation factors in the presence of DMSO were attributed mainly to enhanced complex formation with thiocyanate for a number of heavy metal ions, and for increased differentiation of solvation tendencies in the binary medium. From a semi-quantitative study of species distribution it was concluded that strongly solvated BeSCN⁺ and Be⁺⁺ species predominate under conditions of the described column elutions, although traces of Be(SCN)₂ may be present. The simplicity and convenience of the described procedure suggest wide applicability for isolation or separation ofg to mg amounts of beryllium from concomitant cations, particularly in the presence of large quantities of aluminum and the alkaline earth metals.

---

Zusammenfassung Die selektive Trennung des Berylliums von anderen Metallionen (Cu, Cd, Zn, Ni, Fe, Co, Mg, Ca, Sr, Ba, Al und Pb) wurde erreicht durch Kationenaustausch in 20% iger wäßriger Dimethylsulfoxidlösung, die 0,25-molar an Thiocyanat war. Die Verbesserung der Trennungsfaktoren in Gegenwart von DMSO beruht hauptsächlich auf der verstärkten Komplexbildung einiger Schwermetallionen mit Thiocyanat und auf dem größeren Unterschied der Solvatationsneigung in dem binären Medium. Aus einer semiquantitativen Untersuchung der Verteilungsverhältnisse ergab sich, daß stark solvatierte BeSCN⁺- und Be²⁺-Ionen unter den angegebenen Elutionsbedingungen vorherrschen, wenn auch Spuren von Be(SCN)₂ anwesend sein können. Die Einfachheit des beschriebenen Verfahrens legt dessen Anwendung zur Isolierung oder Trennung von Mikrogramm- bis Milligrammengen Be von Begleitkationen nahe, besonders bei Gegenwart großer Mengen Aluminium und alkalischer Erdmetalle.

     

Contribution of the secondary crystallization to the overall crystallinity of heatset polyester

The crystallinity of poly(ethyleneterephthalate) has been determined by differential scanning calorimetry and by density. The results obtained by calorimetry show that the increment in the crystallinity due to the heatsetting treatment is produced by the increase of the crystallinity corresponding to the premelting endothermic peak.     

Determination of the heatsetting temperature of polyester by TMA

The determination of the effective temperature of the thermal treatment applied to polyester substrates in the textile process has been broadly studied by differential scanning calorimetry (DSC). In this investigation, the authors have studied the possibilities of the thermomechanical analysis (TMA) as a method for the determination of this temperature. For this purpose, fabrics of polyester heatset in an industrial plant between 160 and 210°C, have been analyzed by DSC and TMA. The good results obtained show the possibilities of this technique for the determination of the effective temperature of a thermal treatment. This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetics and Products of Air Plasma Induced Oxidation in Water of Imidacloprid and Thiamethoxam Treated Individually and in Mixture

Imidacloprid (I) and thiamethoxam (T) are widely used neonicotinoid insecticides with high persistence in the environment and thus included in the watch list of substances for European Union-wide monitoring reported in the Decision 2015/495/EU. In this work aqueous solutions of I, T and I?+?T were subjected to advanced oxidation by air plasma produced by negative DC corona discharges above the liquid surface. The oxidative degradation of each pollutant was investigated by monitoring the rate and the products of its decay when treated alone and in the presence of variable amounts of the other compound. The results show that both I and T are readily degraded and that mineralization can be achieved in this process, as proven by the measurement of the residual organic carbon and by the quantitative conversion of chlorine and sulfur into inorganic chloride and sulfate, respectively. The major organic intermediates formed during the complex stepwise oxidation of I and T were identified and monitored by HPLC–MS/MS analysis. The results of kinetic studies show that both for I and T the reaction rate depends inversely on the insecticide initial concentration, that I and T have similar reactivities and that they do not interfere reciprocally in any specific way when treated in mixture at a total concentration of ca 1?×?10^?4 M. Based on literature data and on previous results with the same reactor, it is reasonable to propose that the oxidation of I and T is initiated by the reaction with OH radicals.

     

Electrophilic Vinylation of Thiols under Mild and Transition Metal-Free Conditions

The iodine(III) reagents vinylbenziodoxolones (VBX) were employed to vinylate a series of aliphatic and aromatic thiols, providing E-alkenyl sulfides with complete chemo- and regioselectivity, as well as excellent stereoselectivity. The methodology displays high functional group tolerance and proceeds under mild and transition metal-free conditions without the need for excess substrate or reagents. Mercaptothiazoles could be vinylated under modified conditions, resulting in opposite stereoselectivity compared to previous reactions with vinyliodonium salts. Novel VBX reagents with substituted benziodoxolone cores were prepared, and improved reactivity was discovered with a dimethyl-substituted core.