Thermogravimetric analysis of polyester/cotton blends treated with Thpc-urea-poly(vinyl bromide)

Polyester/cotton fabric swith blend ratios of 0/100, 11/89, 20/80, 30/70, 50/50, and 65/35 were investigated via thermogravimetric analysis in both nitrogen and air atmospheres. The samples were heated from ambient to 750°C at a heating rate of 5°C min^?1. The same fabrics were analyzed after treatment with tetrakis (hydroxymethyl) phosphonium chloride-urea-poly(vinyl bromide) (Thpc-urea-PVBr) flame retardant.Weight losses observed during pyrolysis were assigned to the cotton and polyester portions of the blends. Both cotton and polyester thermally decompose to yield gases and solid char byproducts. In nitrogen the 100% cotton fabric undergoes one major weight loss between 270 and 370°C, with the maximum rate of weight loss, 0.15 mg/min-mg occurring at 346°C. Thermal decomposition of the 100% polyester occurs over a range of 335–470°C, with the peak rate of weight loss, 0.11 mg/min-mg, measured at 416°C. In an air atmosphere, both volatile gases and solid char by- products of pyrolysis undergo combustion. The combustion reactions are associated with measured weight losses. The maximum rate of weight loss for the cotton portion increases to 0.25 mg/min-mg and occurs at 317°C. The maximum rate of polyester decomposition remains the same in both air and nitrogen, but the temperature decreases to 405°C.     

Synthesis and mass spectra of some 1-aroylamino-5-arylaminomethyl-1,2,3-triazoles

The title compounds 2 are prepared from the reaction of 1-(N, N-diaroyl)amino-5-bromomethyl-1,2,3-triazoles with aromatic amines. The fragmentation pattern upon electron impact at 70 eV of compounds 2 is studied. The molecular ion peak is present in all the spectra examined. Besides the [M-28]⁺⁺, there is also a more abundant [M-29]⁺ peak, corresponding to a N₂H loss of the molecular ion. The ion Ar²NH = CH₂ is the base or the most prominent peak.     

Improvement of the chromatographic separation of several 1,4-dihydropyridines calcium channel antagonist drugs by experimental design

A high-performance liquid chromatographic method with diode array detection has been developed and optimized for the separation of five calcium channel blockers belonging to the 1,4-dihydropyridine subgroup (nifedipine and related drugs). The possibility of the simultaneous drug analysis allows a decrease of time during the assay as well as a saving of reagents and solvents. In this work, the effect of four experimental parameters (organic modifier percentage, pH value, concentration of the buffer in the mobile phase, and column temperature) on the chromatographic resolution are investigated by experimental design in order to optimize the chromatographic separation of five 1,4-dihydropyridines (amlodipine, nitrendipine, felodipine, lacidipine, and lercanidipine). Fractional factorial design, central composite design, and finally the Multisimplex program are used to establish the optimal conditions in terms of resolution and minimum analysis time. Optimal separation of the five compounds under study is achieved in less than 12 min using a Sulpecosil LC-ABZ+Plus C18 column, a composition of mobile phase of acetonitrile-10mM acetic acid acetate buffer pH 5 (72:28, v/v) at a flow rate of 1 mL/min, a column temperature of 30 degrees C +/- 0.1 degrees C, and a detection wavelength of 238 nm.     

Synthesis and spectroscopic characterization of 1-[1,2,3-triazol-1-yl]-4-aroylazetidin-2-ones

1-(N-Phenacylidene)amino-1,2,3-triazoles 3 react with propionylchloride and phenoxyacetylchloride in the presence of triethylamine to give trans- ( 5 ) and cis- ( 6 ) 1-(1,2,3-triazol-1-yl)-4-aroylaztidin-2-ones in a 1:1 ratio, on the contrary to the 1-(N-arylidene)amino-1,2,3-triazoles, which do not give any reaction product with the same acid chlorides. The spectroscopic characteristics of these new N-triazolyl-β-lactams are also discussed.     

Dipolar relaxations in the glass transition region and in the liquid crystalline phase of two side-chain liquid crystalline polysiloxanes

The molecular relaxation mechanisms in the glass transition region and in the liquid crystalline phase exhibited by two side-chain liquid crystalline polysiloxanes have been studied by Thermally Stimulated Discharge Currents. These results were compared with those previously obtained by dielectric relaxation spectroscopy. It was observed that two relaxation mechanisms were present in the liquid crystalline phase, and we suggest that these might correspond to the motions of the mesogenic moieties in the liquid crystalline phase. © 1996 John Wiley & Sons, Inc.     

On-Line Multicomponent Determination of the Flux of Mixtures of Phenols Through a Liquid Membrane in Real Time

 The analysis of mixtures of four phenolic compounds in an on-line system using UV-visible measurements with a fibre optic probe is discussed in this work. The aim of this system is to provide accurate real time concentration profiles in order to monitor the transport of phenols across a solid supported liquid membrane in both the feed and stripping phases. Different calibration models are taking into account the pH of the solution, using experimental designs and the first derivative in combination with different multivariate approaches like multiple linear regression (MLR), inverted least squares (ILS) and partial least squares regression (PLS). The comparison of all these combinations is carried out by means of the predictive residual error sum of squares (PRESS) evaluated from an independent set of spectra. From this comparison it is concluded that a PLS model using first derivative spectra offers the most accurate and robust prediction in the permeation experiments. Additionally, the stability of the model and the figures of merit obtained are also discussed. Received July 22, 1999. Revision October 23, 2000.     

Diverse chirped optical solitons and new complex traveling waves in nonlinear optical fibers

This paper studies chirped optical solitons in nonlinear optical fibers. However, we obtain diverse soliton solutions and new chirped bright and dark solitons, trigonometric function solutions and rational solutions by adopting two formal integration methods. The obtained results take into account the different conditions set on the parameters of the nonlinear ordinary differential equation of the new extended direct algebraic equation method. These results are more general compared to Hadi et al(2018 Optik 172 545–53) and Yakada et al(2019 Optik197 163108).     

Potentiometric determination of the protonation constants of some phenols in 1.0 mol/L NaCl at 25°C

The potentiometric determination of the protonation constants of phenol, 2-chlorophenol, 2-nitrophenol, 2,4-dichlorophenol and 2-methylphenol in 1.0 mol/L NaCl at 25°C is presented. An automated system has been used in the experiments. The determination of the constants has been carried out using both graphical and numerical methods.     

Optical image subtraction through speckle modulated by young fringes

A new method for subtracting images is proposed. It is based on assigning complementary Young's fringes to the speckles of the common parts of two images. In this way, carrier frequency is cancelled, and “a-posteriori” spatial filtering shows only noncommon parts. Suggestions on applications of the method are briefly commented.     

Gas phase thermolysis of sulfur compounds. II. Ditertiary butyl sulfide

The pyrolysis of di-tert-butyl sulfide has been investigated in static and stirred-flow systems at subambient pressures. The rate of consumption of the sulfide was measured in some experiments, and the rate of pressure increase was followed in others. The results suggest that the reaction is essentially homogeneous in a seasoned reactor and proceeds through a free radical mechanism. In the initial stages, the decomposition rate follows first-order kinetics, and the rate coefficient in the absence of an inhibitor is given by between 360 and 413°C. The stoichiometry of the uninhibited reaction at 380°C and 50% decomposition is approximately between 360 and 413°C. The stoichiometry of the uninhibited reaction at 380°C and 50% decomposition is approximately.