A study of chemical structure of soft and hardwood and wood polymers by FTIR spectroscopy

Hard and softwood and wood constituent polymers (cellulose and lignin) were studied using Fourier transform infrared (FTIR) spectroscopy. The hollocellulose‐to‐lignin ratio was estimated for some of the timber species. The structural difference between Klason lignin isolated from softwood (Pinus roxberghii and cupressus lusitanica) and hard wood (Acacia auriculaeformis and Eucalyptus tereticornis) species was studied. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1969–1975, 1999     

Tetrafunctional epoxy resins: Modeling the curing kinetics based on FTIR spectroscopy data

The curing kinetics of two thermosetting systems based on a tetrafunctional epoxy resin was investigated by Fourier transform infrared spectroscopy. Two formulations were studied, in which the hardener was an aromatic diamine and a carboxylic dianhydride, respectively. The quantitative evaluation of the epoxy conversion was based on spectra collected in the near‐infrared range (8000–4000 cm⁻¹) as well as in the medium infrared range (4000–400 cm⁻¹). The kinetic parameters evaluated in the above frequency intervals were significantly different. The reasons for such a discrepancy are discussed critically. Several kinetic models, based on the widely employed Kamal approach, were applied to verify their predictive capability. Satisfactory results were obtained for the amine‐cured system, particularly with a modified equation taking into account the autocatalytic nature of the process as well as a limiting diffusional effect. Less accurate results were achieved for the anhydride‐cured system. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 532–540, 1999     

Maleic anhydride-grafted polypropylene: FTIR study of a model polymer grafted by ene-reaction

Ene-grafting of maleic anhydride on polypropylene previously enriched in double bonds by β-scission was promoted in order to obtain model grafted polypropylene. Ene-grafting was carried out in the presence of a radical-scavenger in order to limit at a minimum side-grafting and in presence of catalyst (SnCl₂) in order to maximise the ene-grafting. Nevertheless, it does not lead to high grafting content.Ene-grafted PP confirms the single end-grafted succinic anhydride FTIR assignment at 1792 cm⁻¹ (CO symmetric stretching) while a disubstitution is also observed leading to a shift to a 1784 cm⁻¹ absorption band. This latter band was more generally assigned to interacting anhydride (CO) instead of an assignment to the particular polyanhydride species (as previously assigned by our team [De Roover B, Sclavons M, Carlier V, Devaux J, Legras R, Momtaz A. J Polym Sci, Part A: Polym Chem 1995;33:829. [14]]).     

Study of the Spatio-Chemical Heterogeneity of Tannin-Furanic Foams: From 1D FTIR Spectroscopy to 3D FTIR Micro-Computed Tomography

Tannin-furanic rigid foams are bio-based copolymers of tannin plant extract and furfuryl alcohol, promising candidates to replace synthetic insulation foams, as for example polyurethanes and phenolics, in eco-sustainable buildings thanks to their functional properties, such as lightness of the material and fire resistance. Despite their relevance as environmental-friendly alternatives to petroleum derivatives, many aspects of the polymerization chemistry still remain unclear. One of the open issues is on the spatial heterogeneity of the foam, i.e., whether the foam constituents prevalently polymerize in spatially segregated blocks or distribute almost homogenously in the foam volume. To address this matter, here we propose a multiscale FTIR study encompassing 1D FTIR spectroscopy, 2D FTIR imaging and 3D FTIR micro-tomography (FTIR-μCT) on tannin-furanic rigid foams obtained by varying the synthesis parameters in a controlled way. Thanks to the implementation of the acquisition and processing pipeline of FTIR-μCT, we were able for the first time to demonstrate that the polymer formulations influence the spatial organization of the foam at the microscale and, at the same time, prove the reliability of FTIR-μCT data by comparing 2D FTIR images and the projection of the 3D chemical images on the same plane.     

Rheological study of the curing kinetics of epoxy–phenol novolac resin

The curing reaction of an epoxy–phenolic resin under different conditions was monitored using rheological measurements. The evolution of viscoelastic properties, such as storage modulus, G′, and loss modulus, G″, was recorded. Several experiments were performed to confidently compare the rheological data obtained under varied curing conditions of temperature, catalyst concentration, and reactive ratios. The values of G′ measured at the end of the reactions (at maximum conversion) were independent of the frequency and temperature of the tests in the range of high temperatures investigated. The overall curing process was described by a second‐order phenomenological rheokinetic equation based on the model of Kamal. The effects of the epoxy‐to‐phenolic ratio as well as the curing temperature and the catalyst concentration were also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4430–4439, 2006     

FTIR study of the rearrangement of adsorbed CO species on Al2O3-supported rhodium catalysts

The adsorption of CO at low temperatures (130–293 K) has been investigated on Rh/Al₂O₃ catalysts of low (0.001–1 wt%) Rh loadings by means of Fourier transform infrared spectroscopy. The surface structure of Rh produced at different reduction temperatures (573 and 1173 K) was shock-cooled to 130 K, where the addition of CO caused the appearance of the band due to bridge-bonded CO ((Rh⁰)₂–CO) on all samples. The appearance of the bands due to gem-dicarbonyl (Rh⁺(CO)₂) and linearly bonded CO (Rh_x–CO) depended on the Rh content and the reduction temperature of the catalysts. The positions and the integrated absorbances of the symmetric and asymmetric stretchings of the Rh⁺(CO)₂ changed with temperature. On the basis of the above findings the rearrangement of the adsorbed CO species (indirectly that of surface Rh) is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nondestructive evaluation of polymer coatings by mirage–FTIR spectroscopy: A tool for surface characterization

We demonstrate the unusual applications of the recently developed mirage–Fourier transform infrared (FTIR) spectroscopy for nondestructive characterization of polymer coatings, especially on absorbing substrates or very thin coatings, where conventional FTIR techniques tend to fail. The mirage–FTIR has been briefly described. A few specific examples have been given to demonstrate the potential of this technique as a tool for surface characterization. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1249–1252, 1998     

Influence of different types of UV absorber/UV stabilizer combination on the photodegradation of PC/ABS blend

The polycarbonate/poly(acrylonitrile butadiene styrene) blends, (PC/ABS), are mainly degraded by sunlight known as photodegradation when exposed to outdoor conditions. It is the ultraviolet (UV) radiation that is responsible for the degradation of the blend. To stabilize against the harmful UV radiation and to scavenge the radical species which arise from UV or thermally induced degradation of the PC or the ABS, UV absorbers, and UV stabilizers are used. In this article three different UV absorbers namely, Tinuvin 1577—hydroxyphenyl triazine type, Cyasorb 5411—benzotriazole type, Uvinul 3030—cyanoacrylate type, and two different UV stabilizers, Tinuvin 765—monomeric hindered amine type, Tinuvin 622—oligomeric hindered amine were compounded in different combinations with PC/ABS blend at 240°C using a twin screw extruder. Accelerated aging of the compounded sample was done by Atlas Suntest apparatus. The photodegradation studies were done using UV–vis, attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy, and Yellowing index measurement. The molecular weight of the compounded sample before aging was determined by gel permeation chromatography (GPC). It was found that samples protected with hydroxyphenyl triazine type UV absorber and oligomeric hindered amine show the best result for decreasing the degradation products, oxidation rate, and yellowing of the PC/ABS blend. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

用二维FTIR研究纳米TiO2改性丝素蛋白聚集态结构转变

采用溶胶-凝胶方法制备纳米TiO₂复合丝素膜。UV和SEM测试结果表明,该丝素膜中纳米TiO₂均匀分散在丝素中,TiO₂粒径约为80 nm;同时采用一维红外光谱、二维红外相关光谱对纯丝素膜及复合丝素膜结构进行表征。结果表明,随着纳米TiO₂的生成,丝素蛋白中弱氢键缔合的N—H键以及自由的N—H键发生断裂及重组,生成了强氢键;丝素分子从无序状态转变为有序排列,同时无规线团构象及α螺旋构象向β折叠构象发生转变,最后促使丝素蛋白的结晶构象从Silk Ⅰ转变为Silk Ⅱ。     

Study on the oxidation of calcium sulfide using TGA and FTIR

CaS, generated from H₂S removal process using calcium-based sorbents during coal gasification, is a hazardous chemical. The unstable CaS can be converted to stable CaSO₄ via oxidation. Using Fourier Transform Infrared Spectroscopy (FTIR) technique, the experiments of CaS oxidation were performed in a thermogravimetric analyzer (TGA) qualitatively and quantitatively. FTIR coupled with TGA, which can provide in-situ data in real time, was applied to illuminate the SO₂ evolution in the product gases during CaS oxidation. There is a maximum concentration of SO₂ about 4 min after the CaS reaction starts. The FTIR analyses for the solid products obtained at ambient pressure show that the molar contents of CaSO₄ and CaO both increase with temperature, and the content of CaS diminishes accordingly. However, an exception is that at 950 °C, the conversion of CaS to CaSO₄ by FTIR analyses is lower than that at 900 °C due to the sintering of the product CaSO₄ and the change of the mechanism at higher temperatures. The higher the pressure (1.0 MPa), the more molar contents of CaSO₄ and CaO in the products can be attained, which is more pronounced at lower temperatures. The experimental results indicate that the FTIR technique can be applied to the oxidation of CaS experiments effectively to obtain the contents of the solid products.     

Effects of diffusion on the kinetic study and TTT cure diagram for an epoxy/diamine system

The curing reactions of an epoxy system consisting of a diglycidyl ether of bisphenol A (BADGE n = 0) and 1,2-diamine cyclohexane (DCH) were studied to determine a time–temperature–transformation (TTT) isothermal cure diagram for this system. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and a solubility test were used to obtain the different experimental data reported. Two models, one based solely on chemical kinetics and the other accounting for diffusion, were used and compared to the experimental data. The inclusion of a diffusion factor in the second model allowed for the cure kinetics to be predicted over the whole range of conversion covering both pre- and post-vitrification stages. The investigation was made in the temperature range 60–100°C, which is considered optimum for the isothermal curing of the epoxy system studied. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1931–1938, 1998     

Application of Fourier transform infrared spectroscopy in the study of interactions between PVC and plasticizers: PVC/plasticizer compatibility versus chemical structure of plasticizer

Fourier transform infrared spectroscopy is applied in the study of interactions between PVC resin and plasticizers in flexible PVC systems. The comparison of the theoretical infrared spectra coming from the addition of the respective component infrared spectra with those of PVC/plasticizer experimental systems gives information about polymer/plasticizer interaction degree. In addition, solvation capacity of the plasticizer varies as a function of its chemical structure, giving rise to compatibility differences between the system components. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1731–1737, 2006     

Spectroscopic study of the modification of cellulose with polyethylenimines

The reaction of cellulose with polyethylenimines (PEIs) was studied using diffuse reflectance ultraviolet–visible (UV–vis) spectroscopy, diffuse reflectance FTIR spectroscopy, and standard colorimetry. PEIs were applied from aqueous solutions at the natural pH (pH ～ 11) and at pH = 6. The obtained materials were exposed to different thermal treatments in air. Celluloses treated at pH = 11 suffer the reversible formation of amine bicarbonate salts. This reaction was not observed in celluloses treated at pH = 6 because of the protonation of the amine groups. In all treated celluloses, the PEI amine groups reacted with cellulose carbonyl groups at moderate temperatures to form Schiff bases, which were responsible for the yellowing of the material. At higher temperatures other oxidation products were detected in the UV–vis and infrared spectra. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2196–2202, 2004     

Influence of the network structure and void content on hygrothermal stability of resol resin modified with epoxy–amine

Epoxy–amine was blended with two resol resins to study the influence of the final network and void content on the water absorption of these systems. To characterize the network structure of the blends, infrared analyses were performed. It was observed that a diminution in the crosslink density of the network and the reaction between the epoxy and resol have been occurred. From dynamic–mechanical analyses, a diminution in the T_g value and an increment in the height of the tan δ peak with the epoxy–amine content added to the resol were observed. Thermogravimetric analysis showed that the thermal stability of the resol was reduced by the addition of epoxy–amine as well as a lesser crosslink network for the blends with higher epoxy–amine content. The maximum water uptake and the diffusion coefficient were related with the chemical structure and void content of the specimens. On one hand, the maximum water uptake was observed to depend on the void content of the blends. On the other hand, the diffusion coefficient appears to be related with the local motions of the polymeric chains and with the hydrophilic character of the materials. This behavior was observed for the two resols studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 588–597, 2006     

Stem and bunch banana fibers from cultivation wastes: Effect of treatments on physico‐chemical behavior

Much research related to the use of natural fibers in polymeric matrix composites has been developed. The presence of ? OH groups in the chemical components of the natural fibers generates an important hydrophylic tendency that produces adhesion lacks with hydrophobic polymeric matrices. In this work natural fiber bundles mechanically extracted from both stem and bunch of cultivation banana wastes have been modified by both alkalization and silanization treatments. To evaluate the changes introduced by treatments on the chemical structure of fibers, Fourier‐transform infrared spectrophotometry has been employed. The evaluation of advancing dynamic contact angles along with the determination of total surface free energy by using the Owens–Wendt method indicate that the treatments allow reduction of their hydrophilic tendency by alterations on the physicochemical characteristics of the fibers. This behavior is confirmed by the reduction of moisture uptake, analyzed by thermogravimetric analysis. Small differences on noncellulosic components of stem and bunch fiber bundles have been found. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1489–1495, 2004     

Characterization of the cure of some epoxides and their sulphur-containing analogues with hexahydrophthalic anhydride by DSC and TGA

A series of curing reactions of epoxides and different substituted (1,3-oxo-thiolane-2-thione)s with hexahydrophthalic anhydride in the presence of 2,4,6-tri( dimethylaminomethyl) phenol have been characterized by nonisothermal and isothermal differential scanning calorimetry (DSC). The DSC method was employed to investigate the thermal behavior of the systems cured and to evaluate the short-term stability of one-pot compositions. It was found that the cure processes of novel sulphur analogues of epoxides were generally described through lower (absolute) values of enthalpy of curing; on the other hand, the cure onset and the peak maximum temperatures were considerably higher. To evaluate the thermal stability of the networks obtained, thermogravimetric analysis (TGA) was applied. Its use allowed us to observe that derivatives of (1,3-oxothiolane-2-thione)s were thermally more stable that their analogue epoxides (up to 25°C) and the degradation profiles depended on the steric hindrancesand interactions introduced by the substituents used. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 451–460, 1998     

Monitoring of chemical reactions during polymer synthesis by real‐time attenuated total reflection (ATR)–FTIR spectroscopy

The present study demonstrates in situ real‐time attenuated total reflection (ATR)–FTIR spectroscopy as a powerful tool for monitoring and analyzing different polymerization and polymer modification reactions. Thus, a metallocene catalyzed copolymerization of propene and 10‐undecene‐1‐ol, a polycondensation reaction towards polysulfone, and a modification reaction of OH end groups of hyperbranched poly(urea‐urethane) were investigated successfully. The interpretation of the development of FTIR spectra was carried out on the basis of typical vibration bands of chemical groups of the corresponding monomers and polymers in each case, e.g. of the C?C double bond of 10‐undecene‐1‐ol during the copolymerization, the new C? O? C group of polysulfone, and the new urethane end group of poly(urea‐urethane). Kinetics prediction is also under consideration. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1374–1380, 2006     

用二维FTIR研究纳米TiO2改性丝素蛋白聚集态结构转变

采用溶胶-凝胶方法制备纳米TiO₂复合丝素膜。UV和SEM测试结果表明,该丝素膜中纳米TiO₂均匀分散在丝素中,TiO₂粒径约为80 nm;同时采用一维红外光谱、二维红外相关光谱对纯丝素膜及复合丝素膜结构进行表征。结果表明,随着纳米TiO₂的生成,丝素蛋白中弱氢键缔合的N—H键以及自由的N—H键发生断裂及重组,生成了强氢键;丝素分子从无序状态转变为有序排列,同时无规线团构象及α螺旋构象向β折叠构象发生转变,最后促使丝素蛋白的结晶构象从Silk Ⅰ转变为Silk Ⅱ。     

Application of FTIR spectroscopy for structural characterization of ternary poly(acrylic acid)–metal–poly(vinyl pyrrolidone) complexes

The FTIR spectroscopic technique was used in the study of ternary polymer–metal complexes containing two polyelectrolytes of opposite charge and metal ions. The structure of the ternary (PAA‐Fe³⁺‐PVP) complexes was examined by following the changes in their infrared spectra. It was found that the shapes of the absorption bands of the resultant compounds are influenced by the presence of Fe³⁺. According to this result it was suggested that two types of structure which differ in the composition are formed, one of which results from the coordination of Fe³⁺ with PAA‐PVP complex and the other is due to the formation of Fe³⁺ polycarboxylate. Comparison between the spectrum of PAA‐PVP complex and those of the compounds resulted from the reaction between the two opposite charged electrolytes, PAA and PVP and each of the divalent metal chlorides NiCl₂, CoCl₂, CuCl₂, and ZnCl₂) led to the conclusion that a reaction took place between the divalent transition metal chlorides and the extent of reaction depends on the nature of metal ions and PAA‐PVP complex. The FTIR spectra of the precipitate resulted from the mixtures of PAA‐PVP and Ni(NO₃)₂ or Sr(NO₃)₂ were investigated. It was noted that the addition of Ni(NO₃)₂ or Sr(NO₃)₂ to the mixture of the electrolytes of PAA and PVP provoked appreciable changes in the characteristic spectral features of the complex resulting from the interaction of the metal ions with the polymer–polymer complex. The FTIR spectra of the precipitate resulted from the reaction between CeCl₃, ErCl₃, and LaCl₃ were also investigated. It was concluded that a reaction took place between the rare earth metals and the PPC. This means that ternary polymer–metal–polymer complexes were formed. The extent of changes in the spectral features differs from metal to metal according to the nature of metal ions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2007