用FTIR研究环氧化天然橡胶的热老化

与天然橡胶（ＮＲ）相比,环氧化天然橡胶（ＥＮＲ）具有良好的耐油性和气密性［１,２］,并由于环氧基团而有一定的极性,同其它高聚物的相容性较好．通过环氧基团的二次反应,ＥＮＲ分子链可接上其它的功能团,满足一些特殊的用途［３,４］．对于ＥＮＲ的力学性能、共...     

Study of the composition of low-molecular products of the thermal oxidative destruction of atactic polypropylene by gas chromatography/mass spectrometry

The paper presents the results of studying the composition of low-molecular products of the thermal oxidative destruction of atactic polypropylene by gas chromatography/mass spectrometry. Special attention has been paid to the investigation of the mass spectra of compounds dominating in the composition of low-molecular products of the incomplete oxidative destruction of the original polymer, carried out for the synthesis of components for composite materials of the new generation. The most probable molecular structures of the studied compounds are determined on the basis of fragmentation patterns.     

Characteristics of the thermal decomposition of antituberculous drugs

The thermal decomposition of antituberculous drugs-ethambutol (base and dihydrochloride), isoniazid, ethionamid and pyrazinamid has been studied by DTA, TG and DTG techniques. General remarks have been made on their thermal destruction. The effect of sample size over the range 20–200 mg and heating rate over the range 3–15 deg·min^?1 on the thermal degradation has also been investigated. Moreover, based on the Kissinger’s equation, the values of the kinetic parameters were determined.     

Thermal and structural characterization of superfine down powder

The thermal degradation of down fiber and down powder was studied using TG, DSC, TG-FTIR, and ATR-FTIR as a function of mass loss. For both down fiber and down powder, two evident mass loss stages were observed. Compared to down fiber, down powder had higher moisture and lower thermal stability. The oxygen in air weakened the mass loss of superfine down powder in the temperature range of 300–530 °C, and accelerated the oxidation–reduction reaction between oxygen and powder when the temperature was over 530 °C. The microstructures of down fiber and down powder were investigated on the analysis of DSC results. As the decrease in the average particle size of down powder, the absorbed energy of the destruction of crystallinity, rupture of crosslinks and thermal degradation of peptide bonds decreased, respectively. The gases evolved during thermal degradation of superfine down powder were inspected by in situ FTIR, and then the solid residues collected at different temperature were analyzed using ATR-FTIR. The color evaluation of superfine down powder hot-pressed at high temperature was discussed to confirm the best hot-processing condition.     

The special features of the thermal oxidative destruction of isomeric dipyrrolylmethanes

3,3′,4,4′-Tetramethyl-5,5′-dicarbethoxydipyrrolylmethane-2,2′ and its α,β and β,β isomers were synthesized. The compounds were characterized by recording their proton NMR spectra. The thermal oxidative destruction of the compounds was studied thermogravimetrically. The results were used to determine the temperature and enthalpy characteristics of fusion and the temperatures of the beginning and maxima of the exothermic effects of the destruction of dipyrrolylmethanes in air oxygen. The thermal stability of dipyrrolylmethanes was found to be primarily determined by molecular isomerism and increase for symmetrically substituted α,α-and β,β-dipyrrolylmethanes compared with the α,β isomer.     

Thermal oxidative destruction of complexes of heterocyclic N-oxides with Zn(II)tetra-phenylporphyrin

Thermogravimetry, differential thermal analysis and differential scanning calorimetry were applied for investigation of molecular complexes of heterocyclic N-oxide with zinc(II)tetraphenylporphyrin. The kinetic characteristics of the process of the thermal oxidative destruction for individual compounds and their molecular complexes have been calculated. The obtained results indicate that the complex formation of ZnTPhP with heteroaromatic N-oxides leads to an increase of the thermal stability both the metalloporphyrin and the ligands. It has been shown that the stability of the molecular complexes of ZnTPhP with heteroaromatic N-oxides depends on basicity of the coordinated ligand.     

Degradations photothermiques de polyethylenes reticules. II.—Action photocatalytique d'oxydes metalliques

The chemical modifications of a cross-linked polyethylene sample submitted to photocatalyzed oxidation have been investigated by infra-red spectrophotometry; the spectral changes are compared with those observed in thermal and photothermal oxidation. Zinc oxides and both titanium oxides (anatase and rutile) behaved similarly as photocatalysts. Under excitation by monochromatic light, initial quantum yields of formation of aliphatic ketones have been determined; their variations with macroscopic parameters (excitation wavelength, light intensity, per cent of the photocatalytic oxide) have been studied. Activation energies of the photocatalytic conversion of polyethylene into ketones have been measured under polychromatic light. Finally, it is shown that the simultaneous addition of a photocatalytic oxide and a quinolinic antioxidant is efficient against the oxidative photodegradation of polyethylene.     

The effect of graphite nanoslabs on thermal oxidative destruction of polyethylene

The impact of graphite nanoslabs on thermal oxidation of polyethylene is studied via the methods of dynamic thermogravimetry and isothermal oxidation. Graphite nanoslabs are shown to exert an inhibiting effect on thermal oxidation of polyethylene, which leads to an increase in the induction period and in the oxygen-absorption rate. That there is an abnormal effect of the nanofiller content on the resistance to thermal oxidative destruction of composites, mainly for diffusion reasons, is established as well.     

Preparation and reactivity of metal-containing monomers

Modified polystyrene and polyacrylonitrile possessing cluster fragments in polymer chains have been obtained by radical copolymerization of styrene or acrylonitrile with triosmium carbonyl cluster complexes having double bonds capable of polymerization in their ligand surroundings. The thermal stability of the copolymers produced has been studied by DTG analysis. The temperature increase characteristic of both polymer and cluster pyrolysis has been observed for clusters containing polystyrene. The cluster complexes have been also shown to influence to a great extent the destruction of polyacrylonitrile, thus preventing the formation of stable fused structures in polymer chains.     

Etude thermochimique de quelques benzoates de cuivre(II) solvates

Some compounds of copper(II) benzoate solvated by ligands containing either oxygen (water, alcohol, dioxan) or nitrogen (amines, amides) or both, have been prepared. The thermal decomposition has been studied by TG and ATD methods. The standard enthalpies of formation have been determined and verified by some estimation methods.     

Etude par analyse thermique des sels de calcium de quelques acides alcanesulfoniques

Calcium salts of some alkanesulphonic acids have been prepared. Most of them are new. Their dehydration and the decomposition of anhydrous salts have been studied by thermogravimetric analysis (TG) and by thermal differential analysis (DTA) under ordinary pressure. In an inert atmosphere the sulphides formed indicate that carbon-sulphur and oxygen-sulphur bonds have been broken. The mechanism of decomposition of the calcium alkanesulphonates seems to be more complicated than that of the corresponding carboxylates.     

Synthesis and characterisation of poly(arylene sulphides)—Part II. Thermal analysis studies on poly(phenylene sulphide), poly(2-methyl phenylene sulphide), and poly(2,6-dimethyl phenylene sulphide) and related systems

Poly(p-phenylene sulphide), poly(2-methyl phenylene sulphide) and poly(2,6-dimethyl phenylene sulphide) have been subjected to comparative thermal analysis utilising thermogravimetry and isothermal weight loss studies in air and nitrogen. Comparative thermal stabilities have been evaluated and related to polymer structure. Activation energies for decomposition have been evaluated and are discussed.The related poly(p-phenylene sulphone) and poly(2-methyl phenylene sulphone) have also been studied and their behaviour analysed in the light of their possible formation during thermal oxidative degradation and air curing of the parent poly(phenylene sulphides).     

Titrages “thermochimiques” par formation de fluorures complexes de fer,aluminium, antimoine,etain et plomb

A thermochemical study of the titration of aluminium, iron, copper, lead, tin and antimony salts with sodium fluoride is described. The destruction of fluoride cumplexes by boric acid has been studied. The measurement apparatus consists of two thermistors and a bridge. Clear breaks were obtained for iron, aluminium, copper and lead but no separation of iron and aluminium was possible. The action of boric acid also gave clear breaks in the curves.     

Résonance Magnétique Nucléaire. V.—Etude de Chlorures Vinyliques par RMN 1H. Incréments spécifiques des radicaux alkyle

Twenty five geometrical isomers of vinylic chlorides have been isolated and studied by ¹H n.m.r. and g.l.c; some of these have been chemically reduced for identification. New values of alkyl substituent increments for the estimation of olefinic proton chemical shifts are listed. The effect of chlorine (down field shift) on vinylic allylic and homoallylic protons is described, as well as the solvent effect of benzene (high field shift).     

Diamond Lattice in the Space of Coordination Spheres

An algorithm has been developed for calculating radii, direction vectors, and coordination numbers (c.n.) for an arbitrary number of coordination spheres (CS) of the diamond lattice. It is established that the space of CS of the diamond lattice has imaginary CS in addition to real ones. The imaginary CS are defined by a direction vector, one of the components of which is an imaginary value. The coordination numbers of such CS are zero. For a great number of tabulated CS, we have studied the hierarchies of structural groups (motifs), forming in the space of coordination spheres and determining the X-ray spectra of lattice CS, the crystallomorphological growth forms of diamond crystals, and the forms of diamond fragmentation induced by thermal destruction and melting.     

Thermal and photo-degradation of unstabilized ABS

Thermal- and photo-stabilities of unstabilized acrylonitrile-butadiene-styrene terpolymer, ABS, have been investigated by i.r. spectroscopy. Degradation of ABS samples is initiated by attack on the polybutadiene (PB) component; oxidation products containing hydroxyl and carbonyl groups are produced. The effect of prior thermal processing is to introduce into the polymer hydroperoxides arising from oxidative destruction of PB-unsaturation; these hydroperoxides act as catalysts during subsequent u.v. irradiation. The insolubility of degraded samples of ABS is associated with the formation of cross-linked structures and occurs mainly in the PB segment. It is concluded that the degradation characteristics of ABS are essentially those of the polybutadiene component.     

Influence de la tacticite du polychlorure de vinyle sur son comportement physique en fonction de la temperature

Three PVC samples, having syndiotacticity contents between 55 and 68%, have been prepared and characterized by previously described methods. Their thermal behaviour has been studied using three techniques, viz. inverse chromatography. ATD and Rheovibron. The results make clear the influence of tacticity on both the number and the intensity of transitions. These results are accounted for on the basis of a possible influence of TG conformations on the behaviour of the amorphous phase.     

Studies on the thermal properties of phosphorus-containing polyethyleneterephthalate

Thermal properties have been studied for polyethyleneterephthalate modified with the sodium salt of diethyl phosphite or disodium 1,2-dicarbomethoxyethylphosphonate. The thermal stability of the resin is not adversely affected by the presence of the modifier. The observed energy of activation of the destruction process is decreased in the presence of the modifier.     

Thermal decomposition characteristics of humus horizons from culbin forest

Differential thermal analysis in an oxygen atmosphere and pyrolysis in vacuo combined with mass spectrometry have been used to follow the transformations occurring during the humification of vegetation. Two processes are indicated, one, apparently enhanced by liming consisting of oxidative degradation and the other corresponding to degradation of organic components with high thermal dissociation energies. At the base of some profiles the humus has characteristics close to those of translocated humus in freely drained soils.     

Chemistry in mixtures of Kr with Ar and He illuminated with Kr resonance radiation

The formation and destruction of excited rare-gas dimers have been studied using resonance optical excitation of high-pressure gas mixtures containing Kr. From an analysis of the resulting emission, 19 reaction rate coefficients have been inferred. It is concluded that atom–atom interchange processes play a major role in rare-gas eximer formation, and that stepwise relaxation down the eximer vibrational ladder is less important than multistep relaxation due to atom–atom exchange in the excited eximer.