Reduction in the moisture absorption of cured MY720/DDS epoxy resins

Thin films of cured MY720/DDS epoxy resins were treated with blocking reagents for hydroxyl, amine, and epoxide functional groups. Infrared spectroscopy (IR) and differential scanning calorimetry (DSC) were used to monitor the progress of the reaction. Treated films were soaked in distilled water at 30°C for 720 h, and the corresponding moisture absorption determined gravimetrically. Samples treated with N-methyl-N-t-butyldimethylsilyl trifluroacetamide (MTBSTFA) containing 1% t-butyldimethylchlorosilane (TBDMCS) in dimethylsulfoxide (DMSO) at 30°C showed a maximum reduction in the IR peak at 3400 cm^?1 (OH and NH) of 39% and a 100% reduction in the epoxide peak at 904 cm, ^?1. The moisture absorption was 1.9%, a reduction of 58% compared to the untreated films (ca. 4.5%). The reactions show dependencies on time and temperature and are diffusion controlled. Samples treated with trimethylsilyl isocyanate (TMSI) in DMSO a 70°C showed 72% reduction in the 3400 cm^?1 IR peak; DSC thermograms do not show an exothermic energy, suggesting that all epoxide groups reacted. These reactions are primarily dependent on time and temperature. The moisture absorption of TMSI treated samples was 1.0% (75% reduction). Samples were also treated with m-trifluoromethyl phenyliscyanate (MTFPI). The reduction in the IR peak at 3400 cm^?1 was 9%, but the moisture absorption was 2.4%—a reduction of 47%.     

Structure of Alkali Lignins Fractionated from Ricinus communis and Bagasse. 3. IR Spectra

Abstract

The lignin fractions isolated by one- and multistage soda and sulfate cookings showed almost identical IR spectra, indicating the similarity of the lignin skeletal structure throughout the plant. However, the absorbances reveal some differences. Similarity of the spectra includes: 1) chelation and bonding of the hydroxyl groups. 2) Stretching vibration of C-H bonds in methyl, methoxyl, and methylene groups. 3) Stretching vibration of C≡N. 4) Carbonyl unconjugated β-ketone, conjugated acids, or esters at 1725 cm^?1. There is no change in the intensity of absorption at this band from that at 1515 cm^?1 with the cooking stage. 5) Aromatic skeletal vibration at 1610 and 1515 cm^?1, affected by ring substituents at 1425 cm^?1. 6) The band at 1465 cm^?1 showed a higher intensity for soda and soluble kraft lignins than for insoluble kraft ones. 7) The band at 1370 cm^?1, assigned to phenolic OH bending, is affected by the methoxyl group. 8) The absence of condensed guaiacyl and the presence of syringyl and uncondensed guaiacyl. Assignments for hardwood lignin are shown for soda and soluble kraft lignins of bagasse, while those for softwood lignin are shown for soda, soluble, and insoluble kraft lignins of Ricinus communis and for insoluble kraft lignin of bagasse. A relation exists between the carbohydrate's lignin and the band at 920 cm^?1. Lignins from Ricinus communis are of higher guaiacyl to syringyl ratios than those from bagasse. The presence of C—S vibration and the absence of thiol groups for kraft lignins are indicated.     

Tribological properties of epoxy/polyurea composite

The tribological behavior of epoxy/polyurea composite under dry friction was investigated. The worn surface morphologies of epoxy and epoxy/polyurea composite have been analyzed using scanning electron microscopy (SEM), and the functional group of epoxy and epoxy/polyurea composite before and after wear have been analyzed by a Fourier transform infrared spectrometer (FT‐IR). It has been found that epoxy terminal groups, which exist in an epoxy molecule, can react with the end group amine of the polyurea copolymer, generating more H? O bonds, which enhances the deformation capacity. Polyurea particles are dispersed uniformly in epoxy matrix before wear, while plastic deformation and distorted domains occur on the worn surface of epoxy/polyurea composite. This indicates that the wear resistance of epoxy/polyurea composite was greatly improved by the addition of polyurea elastomer, which led to low frictional coefficients and wear mass losses. Copyright © 2008 John Wiley & Sons, Ltd.     

Structural characterization of ethyl cellulose and its use for preparing polymers with viologen moieties

The characteristics of ethyl cellulose (EC) were studied by chemical reaction and the spectra method. EC was first tosylated with tosyl chloride, and then the tosylated EC (Ts-EC) reacted with sodium iodide (NaI). By comparing the NMR spectra of EC and iodine-substituted EC (EC-I), a free hydroxyl group was proved to exist at the C-6 of the D-glucose unit of cellulose. Viologen moieties were introduced into the EC chain by the reaction of Ts-EC with 4,4′-bipyridine and n-propyl bromide. The existence of viologen was confirmed by ¹H-NMR, IR, and ESR. © 1993 John Wiley & Sons, Inc.     

Molecular and vibrational structure of the extracellular bacterial signal compound N-butyryl-homoserine lactone (C4-HSL)

The molecular and vibrational structure of the title compound (C4-HSL) was studied by experimental and theoretical methods. The infrared (IR) absorption spectrum was measured in the solid state and in CCl₄ suspension. The observed absorption bands were compared with transitions obtained with B3LYP/cc-pVTZ density functional theory (DFT) calculations. Two stable molecular conformations were predicted, corresponding to an endo- and an exo-conformer with similar energies. Intermolecular amide–amide hydrogen bonding in the crystal state was approximated by a simple cluster model, leading to excellent agreement with the observed solid state IR spectrum. Due to the low solubility of C4-HSL in common solvents for IR spectroscopy, such as CS₂ and CCl₄, a liquid solution spectrum of pure, monomeric C4-HSL was not obtained. However, absorbance peaks observed in oversaturated CCl₄ solution could be assigned to distinct contributions from suspended micro-crystalline aggregates and dissolved monomeric species. The key vibrational bands of the monomeric form of C4-HSL are reported here for the first time: 3425 cm^?1 [ν(N–H)], 1784 cm^?1 [ν(CO), lactone], 1688 cm^?1 [amide I], and 1494 cm^?1 [amide II] (CCl₄).     

Analysis of phenanthrene biodegradation by using FTIR,UV and GC–MS

The aim of this paper is to assess the biodegradation of phenanthrene by Flavobacteria FCN2 which was isolated from coke plant sludge via a classical shaken liquid medium enrichment method. The strain FCN2 can decompose phenanthrene (50 mg l^?1) completely within 5 days. The values of pH decrease to 6.7 from 7.2 during degradation periods. And a detailed phenanthrene metabolism was assayed by using FTIR, UV and GC–MS. For FTIR, appearance of new broad absorption bands at 2858 cm^?1, 2927 cm^?1, 2955 cm^?1 and another new strong absorption band at 1734 cm^?1 in metabolites demonstrates that carboxyl group produced during phenanthrene degradation. Besides this, a very strong absorption band appears at 1260 cm^?1. It is ascribed to C–C stretching vibration band in carbonyl group of arone. Two weak adsorption at 334 nm and 349 nm in UV spectra were assigned to the n-π* transition of CO of aldehyde. Two metabolites, phenanthrene-dihydrodiol and naphthalene-1-diol were identified in neutral fraction of phenanthrene degradation by using GC–MS. As a result carboxylic acids and arone were generated during biodegradation of phenanthrene by Flavobacteria FCN2.     

Radiation induced in-situ generation of conductivity in the blends of polyaniline-base with chlorinated-polyisoprene

Radiation induced acid doping of PANI to generate electrical conductivity was achieved by radiation induced HCl release from chlorinated-polyisoprene (ClPIP). Blends of PANI with ClPIP were prepared by mechanical mixing/grinding in the composition range of 9–43% ClPIP by weight and pelletized under 10 t press. The pellets were irradiated in ⁶⁰Co Gammacell in air at room temperature to doses up to 300 kGy. The maximum electrical conductivity increase was observed for the blend PANI43 which changed from 10^?10 to 10^?4 S cm^?1 when it was irradiated to 300 kGy dose. Radiation induced changes on the blends were also studied by UV–vis spectroscopy using reflection technique and FTIR spectroscopy. The broad absorption band in the visible range (630 nm) increased by increasing irradiation dose. The band (1110 cm^?1) in the IR spectra which is indicative of conductivity showed linear correlation with irradiation dose.     

Determination of end groups as a function of molecular size for aliphatic polyesters by derivatization of end groups and size-exclusion chromatography with infrared detection

End groups of poly(ethyleneglycol sebacate) having number average molecular weights less than 2500 were characterized as a function of molecular size by derivatizing end groups separately to form 3,5-dinitrobenzoyl and p-nitrobenzyl esters. A hydroxyl end group was reacted with 3,5-dinitrobenzoyl chloride (DNBC) and a carboxyl end group was reacted with O-(p-nitrobenzyl)-N,N′-diisopropyl isourea (PNBD). After separation of these derivatized polyesters by size-exclusion chromatography, the effluent was monitored by using a highly sensitive infrared detector. Concentrations of polyesters were monitored at 1740 cm^?1 for a carbonyl group in the main chain, polyesters derivatized with DNBC at 1560 cm^?1 for a hydroxyl end group (characteristic absorption band for the nitro group of DNBC), and polyesters derivatized with PNDB at 1537 cm^? for a carboxyl end group (a characteristic absorption band for the nitro group of PNBD). By this technique, three types of polyesters having different end groups were characterized: a diol-type polyester, a mixture of polyesters of a diol type and a mono-ol/monocarboxyl type, and a mixture of polyesters of a dicarboxyl type a mono-ol/monocarboxyl type.     

End‐capping of polystyrene by aliphatic primary amine by derivatization of precursor hydroxyl end group

A new and very efficient route for the synthesis of aliphatic primary amine terminated polystyrene (PS) is reported. In contrast to most known methods, only traditional commercially available reagents are used. PS is synthesized by anionic polymerization with a lithium counter ion and the living chains are end‐capped by a hydroxyl group upon addition of ethylene oxide followed by protonation. The ω‐hydroxyl end group is tosylated and the tosylate is then reacted with sodium azide. The azide terminal group is finally reduced into primary amine. The different steps of functionalization have been fully characterized by SEC, ToF‐SIMS, FTIR, and ¹H NMR. The amine content (= 98%) has been determined by acid‐base titration with perchloric acid. It clearly shows the efficiency of the synthetic method reported in this article although it is a multistep method. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1618–1629, 2000     

Some 1-substituted quaternary imidazolium compounds and related polymers: Qualitative and quantitative infrared analysis

It was found that 1-substituted quaternary imidazolium compounds show some characteristic infrared (IR) activity. On quarternization of 1-substituted imidazoles strong absorption bands appeared at about 1150 and 1550 cm^?1 in the IR spectra of these compounds. The band at 1150 cm^?1 was assigned to the position 2 C?H bending mode and the 1550 cm^?1 band was attributed to a ring vibration mode of the quaternary imidazolium compounds. The concentration of the quaternary imidazolium units in a polymer can be determined by measuring the intensity of the absorption bands at 1150 or 1550 cm^?1 in relation to another suitable absorption band of the spectrum.     

Study of the IR spectra of the products of the ethanolysis of oak and pine lignins

Summary The IR spectra of a number of compounds formed in the ethanolysis of the lignin of foliate and coniferous species have been studied using samples of ethanol lignin, vanillin, syringic aldehyde, p-hydroxybenzaldehyde, guaiacylacetone, coniferyl and sinapic aldehydes, vanilloyl methyl ketone, -hydroxypropiovanillone, -ethoxypropiosyringone, and vanillic and gallic acids. Differences in the absorption at 1330–1340 cm^–1 have been found in the spectra of samples of ethanol lignin from oak and pine. Oak lignin has a strong maximum which is absent in pine lignin. Thus, the lignins of foliate and confierous species can be distinguished by the absorption in the spectral region from 1330 to 1340 cm^–1.Khimiya Prirodnykh Soedinenii, Vol. 3, No. 2, pp. 208–213, 1967     

Demonstration of cavity enhanced FTIR spectroscopy using a femtosecond laser absorption source

A proof of principle experiment was performed by recording the cavity enhanced absorption spectrum of the weak b–X transition of molecular oxygen in the atmosphere using a Ti:Sa femtosecond laser as an absorption source and a high resolution continuous scan Fourier transform interferometer. The cavity was mode matched and either continuously scanned or stabilized at the so-called magic point. An optimal rms noise equivalent absorption of 3 × 10^?7 cm^?1 Hz^?1/2 was reached in the latter case, corresponding to α_min = 3 × 10^?7 cm^?1.     

Interpretation of the IR spectrum of methyl-β-D-glucopyranoside based on the theoretical calculation of frequencies and intensities of normal vibrations

For the first time the detailed interpretation of the IR spectrum of methyl-β-D-glucopyranoside is presented based on the complete calculation of frequencies of normal vibrations and absolute intensities of IR absorption bands and on their comparison with the corresponding experimental values. The characteristic spectral features of oxymethyl substitution for the hydroxyl group are detected. The regularities in the formation of the complex band structure in a frequency range from 1150 cm^?1 to 950 cm^?1 is determined.     

Electrochemical oxidation of primary amine in ionic liquid media: Formation of organic layer attached to electrode surface

Electrochemical oxidation of primary amine in ionic liquid media has been investigated. The ionic liquid chosen for this study was 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Two primary amine compounds are used for this study; 4-nitrobenzylamine and 2-aminoethylferrocenylmethylether. The oxidation of the amino compounds in ionic liquid conduces to the modification of the electrode surface. The modified electrodes were characterized by cyclic voltammetry and XPS analysis. Both techniques support the presence of an organic layer strongly attached onto the electrode surface. The surface concentration of the attached group obtained in this media was found to be around 1 to 3 × 10^?10 mol cm^?2. The use of ionic liquid as media for the grafting leads to decrease of the surface concentration of the grafted layer; and the formation of less dense layer compared with classical solvent such as acetonitrile.     

Silver nanowires-copper sulfide core/shell nanostructure for electrochemical supercapacitors

This paper reports the synthesis of a new hybrid core (silver nanowires (AgNWs))/shell (copper sulfide (Cu₂S)) nanostructure using simple and inexpensive drop casting and successive ionic layer adsorption and reaction (SILAR) methods. The effects of the thickness of the Cu₂S shell on the Ag NW core on the electrochemical properties of the nanocomposite were studied by varying the number of SILAR cycles from one to four. The structure and microstructure of the prepared composite nanostructure electrode materials were characterized by X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. The AgNW/Cu₂S exhibited a high specific capacitance of 603 Fg^?1 (stainless steel substrate) and 707 Fg^?1 (Ni foam substrate) at a scan rate of 10 mVs^?1 with an energy density of 10.01 Whkg^?1 and 25.33 Whkg^?1 at an applied current of 0.2 mA. This study provides a simple and cost-effective strategy for the fabrication of nanostructured electrodes for supercapacitor applications.     

Analysis and identification of irradiated Spirulina powder by a three-step infrared macro-fingerprint spectroscopy

A three-step infrared (IR) macro-fingerprint method combining conventional IR spectra, and the secondary derivative spectra with two-dimensional infrared correlation spectroscopy (2D-IR), was developed to analyze Spirulina powder before and after gamma irradiation. In the IR spectra, most of the absorption peaks of samples irradiated at 1, 2.7, 6, and 10.4 kGy had lower intensities than the non-irradiated ones, whereas peaks at 1152, 1078, and 1051 cm⁻¹ were slightly enhanced with irradiation at 2.7, 6, and 10.4 kGy. Their second derivative spectra amplified the differences and revealed that irradiation affected the C=O band of carboxylic acid and esters, and the N–H band of proteins. The peaks at 1746 and 1741 cm⁻¹, and those at 1730 and 1725  cm⁻¹ became two broad peaks. Meanwhile, the three sharp peaks at 1548 cm⁻¹, 1544 cm⁻¹ and 1536 cm⁻¹ changed to two broad peaks at around 1547 and 1534 cm⁻¹ after irradiation at doses higher than 1 kGy. The characteristic IR bands from 1700 cm⁻¹ to 1600 cm⁻¹, which represent the C=O band in proteins, also have different shapes and intensities after irradiation. The finding indicated that irradiation affected the secondary structures of protein which was confirmed by curve fitting results. During the process of increasing the temperature from 50 to 210 °C, the ratio of amide I to II in absorption intensities in the 2D-IR spectra of the irradiated samples varied with different response for different samples. Saccharides in Spirulina powder had a higher thermostability than proteins, but the autopeaks of irradiated samples did show differences from the non-irradiated sample. The intensity of autopeaks at 1012 cm⁻¹ increased dramatically in the irradiated samples while that of peaks at 1053, 1071, and 1083 cm⁻¹ decreased after irradiation. Based on the three-step IR macro-fingerprint method, irradiated Spirulina powder samples were successfully and fast identified and discriminated.     

Vibrational spectroscopy studies of structural changes in lignin under microwave irradiation

Structural changes that occur in lignin surface-modified with nickel nanoparticles during microwave- assisted dry reforming (DR) are studied via vibrational spectroscopy. IR spectroscopy reveals that the nickel deposition has a considerable effect on the structural characteristics of lignin. It is found that nickel deposition from an acetate salt substantially reduces the intensity of absorption bands at 1700 cm^?1. This finding suggests that Ni(2+) interacts mostly with formate groups, which are subsequently oxidized to carboxylate groups. It is shown that with the deposition of metallic nickel particles from a colloidal nickel solution in toluene prepared via metal vapor synthesis, the nickel particles do not interact with the surface functional groups of the lignin. Deep conversion of an organic mass of lignin by DR to form synthesis gas reduces the intensity of the absorption bands of the identified functional groups and raises the intensity of the absorption bands of the aromatic rings. Raman spectroscopy shows that during lignin conversion, the aromatic rings condense partially to form amorphized graphite. In operando studies reveal that the DR of nickel-modified lignin heated to 200–400°C results in the isolation of vanillic oxygenates that are probably intermediate products of reforming.     

The effect of additives of strong inorganic acids on IR-spectroscopic determination of water in organic solutions

The possibility of the quantitative determination of water in organic solvents containing strong acids by IR spectrophotometry at 3500–3700 cm^?1 was studied. The molar absorption coefficients at the maximum of the most intense absorption bands of water in acetonitrile, chloroform, and 1,2-dichloroethane were 115, 43, and 88 M^?1 cm^?1, respectively. The study of the effect of acid additions to acetonitrile showed that hydrochloric and nitric acids had little on the shape and intensity of the IR spectra of water. The presence of perchloric acid reduces the intensity (for 0.027 M HClO₄, by 40% at 3618 cm^?1), which was due to the state of acids in the solvents. Conductometric measurements showed that, under these conditions, HCl and HNO₃ were unionized, while HClO₄ dissociated almost completely.     

FTIR assessment of poly(ethylene oxide) irradiated in solid state,melt and aqeuous solution

FTIR spectroscopy was used to study poly(ethylene oxide), PEO, irradiated in solid and molten aggregate states and as aqueous solutions of various concentrations. The changes in shape and width of –C–O–C– complex absorption intensities at around 1112 cm^?1 were the most prominent. On irradiation of solid samples in contact with air shrinking of –C–O–C– complex and increase in its absorption intensities indicated predominant degradation. Crosslinking prevailed on irradiation of molten PEO and of its aqueous solutions in nitrogen atmosphere and manifested itself as widening of –C–O–C– absorption and decrease of corresponding intensities. Partial or complete merging of CH₂ wagging vibrations at 1342 cm^?1 and 1360 cm^?1 that are characteristic of crystalline PEO into a single absorption at around 1350 cm^?1 indicated amorphization what was observed for samples that had reduced degree of crystallinity determined by differential scanning calorimetry. DSC could not discriminate between degradation and crosslinking while the changes in width and shape of –C–O–C– complex were independent of the changes in crystallinity. Comparison of FTIR spectra of the same PEO samples obtained as thin film and as KBr pellets revealed that pellet preparation results in a number of spectral artefacts.