Search Results
Abstract
In this work thermal stability and tensile strength of polyurethanes obtained from glycolysates was investigated. The glycolysates were produced via glycolysis of waste polyurethane foam (PUR) in the reaction with 1,3-propylene glycol (PG). Polyurethanes were synthesized from the obtained intermediates by the prepolymer method using diisocyanate (MDI) and glycolysis product of molecular mass ranging from 700 to 1000, while 1,4-butylene glycol (BDO) was used as a chain elongation agent. The influence of NCO group concentration in prepolymer on tensile strength and elongation at break of polyurethanes was investigated using Zwick universal tensile tester. Thermal decomposition of the obtained glycolysates and polyurethanes was followed by TG coupled with FTIR spectroscopy. The main products of thermal decomposition have been identified.
Abstract
The catalytic effects of iron, aluminum or silicon on the formation of NOX precursors (HCN, NH3 and HNCO) and HCl during wheat straw pyrolysis were studied using a thermogravimetric analyzer (TG) coupled with a Fourier transform infrared (FTIR) spectrometer in argon atmosphere. The results show that the presence of iron, aluminum or silicon decreases conversion of straw-N into NH3 with the sequence of Fe > Si > Al. The iron or silicon addition suppresses N-conversion into HCN and HNCO, and the aluminum addition has no notable influence on HCN emission during pyrolysis. The share of N-conversion to NH3 and HCN increases, but that to HNCO and NO decreases a little in the presence of added iron, aluminum or silicon. The addition of SiO2 results in the highest HCl removal efficiency.
New complexes of heavy lanthanides with 4,4′-bipyridine and trichloroacetates
Synthesis, thermal and other properties
. Coupled TG–FTIR measurements were carried out using a Netzsch TG 209 apparatus coupled with a Bruker FTIR spectrophotometer. Samples of about 13.04 mg for Ho(III) and 11.3 mg for Tm(III) compound were heated up to 1000 °C at heating rate of 10 °C min −1
contains a considerable amount of S as a consequence of the chemical treatment, which explains its use as fertilizer. The higher percent of Si in the ash sample is a product of the thermal decomposition, as assessed by TG, FTIR, and X-ray diffractometry
series of lanthanide complexes with 4,4′-oxybis(benzoic) acid obtained under hydrothermal conditions. The thermogravimetric (TG), differential scanning calorimetry (DSC) methods in air and TG-FTIR coupled technique in nitrogen were used to study the
investigate by complexometry, elemental analysis, infrared spectroscopy, simultaneous thermogravimetry and differential thermal analysis (TG–DTA), differential scanning calorimetry (DSC) and TG-FTIR techniques. The thermal studies were performed in dynamical
associated with a strong exothermic effect reflected on the DTA curve. TG-FTIR analysis The decomposition process connected with the gas product analysis was carried out for the Sm and Ho complexes. The FTIR spectrum of
Thermal stability and structure of a new co-crystal of theophylline formed with phthalic acid
TG/DTA-EGA-MS and TG-EGA-FTIR study
Abstract
A new co-crystal of theophylline and phthalic acid with 1:1 molar ratio has been prepared. It crystallises in the monoclinic crystal system, space group P21/c, a=11.5258(9), b=10.1405(6), c=13.9066(12) Å, β=106.827(4)°. The structure of the co-crystal has been revealed by single crystal X-ray diffraction. An infinite helical polymeric chain is formed by intermolecular hydrogen bonds of the two neutral constituents. The hydroxyl group and carbonyl oxygen atom in one of the carboxyl groups of phthalic acid form hydrogen bonds to O6 and to N(7)H atoms of theophylline, respectively, while the other carboxyl OH group of phthalic acid is in hydrogen bond to N9 atom of theophylline by very strong intermolecular interactions proven by 1883 cm−1 centred peak in FTIR spectrum. Thermal degradation of this new supramolecular compound is a two-step process in air. At first phthalic acid (47.4%) released up to 230°C, meanwhile it loses water and transforms into phthalic anhydride. In EGA-MS spectra, the characteristic fragments of water (m/z=17, 18) appear from about 180°C, while absorption bands of phthalic anhydride are shown in EGA-FTIR spectrum at about 210°C. In the second step theophylline begins to sublime, melts at 276°C, and then evaporates up to 315°C with minute residues.
Abstract
In this work thermal transitions and thermal stability of polyurethane intermediates and polyurethanes were investigated. The intermediates were obtained by glycolysis of waste polyurethane (PUR) in the reaction with hexamethylene glycol (HDO). The excess of HDO was not separated from the product after the glycolysis process was finished. The effects of different mass ratio of HDO to PUR foam on selected physicochemical properties (hydroxyl number, Brookfield viscosity and density) were also determined. The polyurethanes were synthesized from the obtained intermediates by the prepolymer method using diisocyanate (MDI) and glycolysis product of molecular mass in range 700/1000 g mol–1. Hexamethylene glycol, 1,4-butanediol and ethylene glycol were used as chain extender agents. Influence of NCO groups concentration in prepolymer on glass transition temperature (T g) and storage and loss modulus (E’, E’’) of polyurethanes were investigated by the DMTA method. Thermal decomposition of obtained glycolysates and polyurethanes was followed by thermogravimetry coupled with Fourier transform infrared spectroscopy. Main products of thermal decomposition were identified.
