An FTIR spectroscopic study of the photodegradation and thermal degradation of wool

The effect of sunlight on untreated, sulphamic acid-treated and FBA-treated wool has been investigated using infra-red spectroscopy coupled with second-derivative spectral analysis. The effect of heat on untreated and treated wool fabrics has also been studied. Changes in the oxidised cystine species were observed as a result of both thermal oxidation and photo-oxidation.     

Analysis of thermal degradation for plastic optical fibers

Attenuation loss of plastic optical fibers (POFs) gradually increases with long use at high temperatures. We separated attenuation loss of the POFs before and after heating at 150°C in air into four loss factors, and identified the main factor for attenuation loss increase as electronic transition absorption loss (α_e). The increase of α_e was caused by a thermal oxidation reaction of the core polymer in the POF. But, according to NMR and FT-IR spectra, elementary analysis, etc., hardly any reaction products were detected. We assume that the reaction products were only a small amount of the conjugated carbonyl groups. So we fabricated POFs containing model compounds with conjugated carbonyl groups, and measured their attenuation loss. The attenuation loss spectra of these POFs were similar to those of thermally degraded POFs. Consequently, a very small amount of conjugated carbonyl groups were formed by the thermal oxidation reaction of core polymer so that α_e increased to an unacceptable level.     

Dielectric spectroscopic study of wood plastic combinations

Curing of wood-polyester combitions was studied by recording dielectric spectra as a function of temperature at fixed frequency at different stages of cure and as function of cure-time at fixed temperature. The measurements were preformed by a specially constructed continuously recording spectrometer equipped with linear temperature program. By measuring the shifts of the dielectric transition temperatures it was possible to follow changes of the molecular mobilities in the resin as crosslinking proceeded. By measuring the relative intensities of the dielectric absorption the change of the concentration of the polar groups as a function of cure time could be followed. The existence of a stepwise aftercuring waw revealed.     

采用红外光谱法研究贝壳粉对PVC热降解行为的影响

采用红外光谱法研究了不同温度下贝壳粉对PVC热降解行为的影响。结果表明,具有碳酸钙成分的贝壳粉虽然本身热分解温度很高,但作为PVC的热稳定剂效果并不理想,这对今后研究贝壳类助剂具有指导意义。     

The thermal degradation of some poly(fluorethers)

A series of poly(fluoroethers) has been studied by thermogravimetry, pyrolysisgas chromatography–mass spectrometry and fluoride ion analysis. The thermal stabilities are lower than those of a vinylidene fluoride/hexafluoropropene copolymer. Primary chain scission occurs at O—CH₂ links. Rearrangement processes giving rise to cyclic compounds are important for polymers containing aromatic or heterocyclic rings in the chain.     

IR spectroscopic study of water in the structure of binary alkali borate glasses

The influence of the synthesis conditions and composition of binary sodium and potassium borate glasses on the spectral absorption in the wavelength range 2.5–4 µm due to the presence of structurally bound water is investigated. It is demonstrated that water in the structure of alkali borate glasses, as in the structure of alkali silicate glasses, can exist in the form of so-called free and bound hydroxyl groups that are incorporated into the glass network in different ways. The ratio between the numbers of these forms of structural water in borate glasses is determined by the synthesis conditions and composition of the glass. The synthesis under different conditions makes it possible to prepare glasses not only with different water contents but also with different ratios between the numbers of free and bound hydroxyl groups.Original Russian Text Copyright © 2005 by Fizika i Khimiya Stekla, Golubeva, Pavinich.     

A study of the thermal degradation of polystyrene by thermal volatilization analysis

A TVA study of several anionic polystyrene samples, having number average molecular weights in the range of 4.6 × 10³ to 2 × 10⁶, reveals a hitherto unobserved molecular weight dependence of the overall apparent Arrhenius preexponential factor as determined by the method of Roche.² The latter effect is discussed in terms of a model in which the zip length and chainscission rate constants are both functions of molecular weight. It is suggested that the functional dependence of the kinetic parameters on molecular weight is a reflection of their hydrodynamic coupling to the viscosity of the molten polymer.     

Kinetic study on the first stage during thermal degradation of polystyrene

The kinetic parameters of the first stage of polystyrene degradation have been investigated to elucidate the reaction mechanisms using the flow reactor system. The decrease in molecular weight of polystyrene was recorded at minute intervals over the temperature range 310°–390°C. Generally, the first and second stages were observed by thermogravimetric analysis (t.g.a.), however in the early stage of the degradation volatile yields of at least 5% occurred. Therefore, using t.g.a. analysis it is difficult to detect this earlier stage. It became evident that the first stage in the earlier part of the reaction could be detected by g.p.c. analysis. We have observed the hidden kinetic parameters of the nature of the first stage of the polystyrene degradation. The results indicate that the main chains were degraded randomly with the small quantitative volatile groups in the first stage and the rates of decrease in molecular weight in the first stage against reaction temperatures were evaluated as log k_s = 12.0 ? 41300/RT.     

Photoacoustic study of thermal degradation of polyurethane

Polyurethane rigid foam shows substantial changes in its photoacoustic absorption spectra (PAS) on heating in the presence of air. These spectral changes are due to conjugated structures and quinone–imide formation, formed during degradation. The mechanism of degradation appears to be free radical in nature.     

Thermogravimetric study of thermal degradation of polyetherimide

Thermal stability in nonoxidizing atmosphere of a polyetherimide (PEI) is investigated by thermogravimetry (TG). It is observed that thermal degradation of this product consists of two overlapping processes, which are conveniently separated by fitting the TG curves to mixtures of generalized logistic functions. Thus, each process is represented by a single function. The analysis of the fitting parameter values obtained for the main degradation process in different isothermal and heating ramp conditions allows to obtain insightful kinetic parameters (critical temperature, energy barrier, and reaction‐order) which allow to make predictions in both isothermal and nonisothermal contexts. There is a minimum temperature for each process to occur and a ramp‐energy barrier related to the process rate. In the ramp context, the values of these two parameters explain that, although one process starts at lower temperature, it proceeds at a very low rate until reaching temperatures at which the other process goes much faster. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42329.     

IR spectroscopic study of the phase composition for sodium silicate synthesized in aqueous medium

The distribution of components, phase composition, and structural features of sodium silicate synthesized in aqueous medium were investigated by IR spectroscopy. In prolonged storage in air, the substance partially cracked and its phase composition changed. Sodium silicates of different stoichiometry, free silica in the form of cristobalite, and sodium carbonate were the basic phases. The concentration gradients of sodium carbonate and water in the silicate in ambient conditions intensified from center to edges. Generation and development of cracks that perturbed the continuity of the synthesized substance were explained. It was noted that water sorbed from air is more dangerous for degradation of the structure than structurally bound water from the initial solution. __________ Translated from Steklo i Keramika, No. 1, pp. 6–10, January, 2007.     

Characterisation of some Australian oil shale using thermal, X-ray and IR techniques

Thermogravimetric analysis (TGA), Diffuse Reflectance Infrared Fourier Transforms Spectroscopy (DRIFTS) and X-ray diffraction (XRD) were used in conjunction to characterise oil shale samples from an Australian Tertiary oil shale deposit. Results from these techniques were compared with conventional Modified Fisher Assay (MFA) data. DRIFTS and TGA results showed clear correlations with each other as well as with the MFA values. DRIFTS results indicated that most of the kerogen is in aliphatic hydrocarbon form. It was evident from TGA analysis that the weight loss in the 450-550 °C temperature region has a strong and direct correlation with the amount of oil in the samples, as determined by the MFA method. Calibration curves were generated in which oil content can be predicted from TGA and DRIFTS data. The combination of TGA and DRIFTS is mostly useful in examining organic matter in oil shale while DRIFTS and XRD combination is useful in examining the minerals phases. XRD and DRIFTS showed good agreement in identifying the presence of minerals such as quartz, clay and carbonates. Combination of these three techniques can provide an alternative and inexpensive method to the MFA analysis in determining the kerogen content, while overcoming the limitations of each other.     

阻燃热塑性聚酯弹性体的热降解动力学研究

采用阻燃剂与单体共聚合成阻燃共聚热塑性聚酯弹性体(FR-TPEE),对FR-TPEE进行热失重分析,并采用Kissinger法,Flynn-Wall-Ozawa法和Coats-Redfern法对FR-TPEE热降解动力学进行研究。结果表明:FR-TPEE热降解过程分3个阶段,Kissinger法计算其活化能偏小,Flynn-Wall-Ozawa法和Coats-Redfern方法不适用于处理FR-TPEE热降解第三阶段。Coats-Redfern方法得知FR-TPEE第一阶段的降解机理是相界面控制反应机理,第二阶段是一维扩散机理。     

The application of some modern analytical techniques to thermal degradation studies

Studies of the thermal degradation of polymers were stimulated first by processing problems and subsequently by the requirements of applications in more and more extreme environmental conditions. These problems were solved largely by the use of stabilising additives discovered by trial and error methods. Later, as increasing emphasis was placed upon toxicity of products evolved from thermally degrading or burning polymers, the great analytical revolution which has been taking place during the past 20–30 years has made it possible to analyse the products and mechanisms of degradation with great accuracy. Examples are presented on the use of thermal analysis, chromatographic and spectroscopic techniques in the solution of analytical problems encountered in the degradation of a number of materials including bromine-containing copolymers, chlorinated rubber, polyurethanes, polymethacrylonitrile, copolymers of styrene and acrylonitrile and polysiloxanes.     

Errors that result from thermal degradation during shear measurements on some molten polymers

Shear sensitivities of molten polymers may be determined from measurements made on individual samples subjected in one test to a series of either increasing or decreasing shear rates. Many polymers, including polyesters, degrade when molten. If the effect of degradation is significant, and is ignored during data analysis, a significant error could result. The magnitude of the error depends directly on the magnitude of the reaction rate constant for degradation, which differs from polymer to polymer and which increases as temperature increases. In rheological characterization of molten polymers, one should know or determine the degradation behavior of the polymer being investigated and then account for it in the data analysis. Experimental results for poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) are presented and discussed. Ways to account for degradation in shear sensitivity measurements are also presented.     

Instrumental methods for the study of the thermal degradation of polymers

After consideration of the objectives of a degradation study, product fractions, and experimental variables, an attempt is made to assess the applicability of various instrumental methods to particular objectives. The technique of thermal volatilization analysis (TVA) is discussed in greater detail. Several examples are discussed from degradation investigations to illustrate important aspects of experimental approach.     

IR spectroscopic study of the phase composition of boric acid as a component of glass batch

Analytically pure reagent “boric acid,” used in batches for preparing glass, was investigated by IR spectroscopy. It was found that the reagent consisted of three components — meta-and orthoboric acids and glassy boron oxide, water was present in two forms — molecular and in the form of OH groups, and impurities of organic substances and carbon dioxide were not very probable. The orthoboric acid bands at 1450, 1195, 883, 815, and 548 cm⁻¹ were found for the first time and were not indicated in the previously published reference spectrum. __________ Translated from Steklo i Keramika, No. 2, pp. 8–12, February, 2007.     

In situ IR spectroscopic study of poly(N-vinylcarbazole) film during electrochemical doping

In Situ IR spectroscopic study was made on the electrochemical doping of poly(N-vinylcarbazole) (PVK) by the subtractively normalized interfacial Fourier transform technique. The results show that the doping of ClO anion is limited by crosslinking of the polymer. The structure of doped PVK film depends on electrode potential and reaction time. Maximum doping of PVK may be achieved using a low oxidation potential for a proper reaction time. © 1996 John Wiley & Sons, Inc.     

IR spectroscopic investigation of the effect of deep UV irradiation on PET films

Infrared spectroscopy provides a comprehensive view of chemical and conformational structures of molecules. Spin cast amorphous and semicrystalline PET thin films on silicon substrates were investigated with transmission IR to reveal the effect of deep UV (172 nm) irradiation on molecular architecture. Difference spectra by subtracting original samples from the UV treated ones show features consistent with a Norrish type I based decarbonylation and a Norrish type II process producing terminal carboxylic acid groups. Conformation selectivity of the photochemistry is discussed on the basis of three major structure factors related to the formation of a cyclic transition state of the Norrish type II process. Quantitative analysis was carried out by simulating carbonyl stretching band in the difference spectra with ester and acid type carbonyl model spectra. The effects of UV fluence and molecular mobility on quantum yields were elucidated. Quantum yields of 172 nm UV photochemistry in bulk PET were calculated to be no different from those of longer wavelength (200-400 nm). UV modified depth were also estimated by means of plasma etching of the samples.