An Anomalous Effect in the Drift Spectra of Woods and Papers

Diffuse Reflectance Fourier Transform Infrared (DRIFT) Spectroscopy is a very useful and convenient means of obtaining the infrared spectra of woods and papers. However, distortions can occur in the intensities of bands in the region 950–1200 cm^?1 when the spectra are obtained by reflection directly from wood and paper surfaces due to interference from specularly reflected radiation. Such distortions are reduced in spectra obtained from very thin sheets of paper of from fibres diluted in potassium bromide.     

Detection of Pinosylvins in Solid Wood of Scots Pine Using Fourier Transform Raman and Infrared Spectroscopy

Abstract

Diffuse reflectance Fourier transform infrared (DRIFT) and near infrared (NIR) FT-Raman spectroscopy were used to detect pinosylvins in the wood of Pinus sylvestris L. trees. NIR FT-Raman spectroscopy offered the possibility of revealing pinosylvins simply by visual inspection of Raman spectra whereas DRIFT spectra needed a more complicated evaluation. Pinosylvin and resin acids from Scots pine were examined as to the possibility of their being the cause of observed spectral differences between sapwood and heartwood. Since pinosylvins are important compounds for the decay resistance of Scots pine wood, the detection of pinosylvins with Raman spectroscopy might be used to assess durability of wood products.     

Structural and Concentration Effects on the Diffuse Reflectance Ftir Spectra of Cellulose,Lignin and Pulp

Experiments were conducted to determine the effect of sample type and concentration on the diffuse reflectance infrared fourier transform (DRIFT) spectra of unbleached softwood kraft and thermomechanical pulps, microcrystalline cellulose (Avicel) and kraft lignin (Indulin AT). The absorption of characteristic bands, in Kubelka-Munk units, was followed as a function of sample concentration in potassium bromide, and, in the case of the two pulps, was also determined on handsheets. Anomalous dispersion occurred at concentrations of 1% or below. This phenomenon resulted in a decrease of absorption of specific bands with increasing concentration and was particularly significant for kraft pulp, less important for thermomechanical pulp and microcrystalline cellulose, and practically absent in pure kraft lignin. These effects of specular reflectance could not be completely eliminated by diluting the sample in a non-absorbing matrix, as previously claimed, but could only be minimized at low concentrations.     

Effect of treatment temperature on the amination of chlorinated diamond

The amination of a diamond surface was investigated by treatment of chlorinated diamond in an ammonia environment at various temperatures. The chlorinated diamond was prepared by irradiating hydrogenated diamond with ultraviolet (UV) light in the presence of elemental chlorine. Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy of the chlorinated diamond showed a strong peak corresponding to the C–Cl stretching mode, which has not been reported in previous studies on chlorinated diamonds. The types of amines formed on the diamond surface were strongly affected by the temperature used for the reaction. DRIFT spectra of aminated diamonds indicate that amination at room temperature results in formation of NH₄⁺. Amination at 373 K showed DRIFT peaks corresponding to CN vibration and NH₂ scissoring. At an amination temperature of 573 K, most of the nitrogen on the surface was present as imines.     

Analysis of Solid Wood Surfaces by Internal Reflection Fourier Transform Infrared Spectroscopy (FTIR-IRS)

The refractive index of white fir wood in the infrared region of the spectrum was determined by a measurement of the critical angle in FTIR-IRS to be 1.43. The depth of light penetration into wood (decrease in the original light intensity to 1/e) was calculated to be 0.13–2.15 μm depending upon the wavelength of light, angle of incidence, and the refractive index of the prism used. It was found that the signal-to-noise ratio in FTIR-IRS of wood could be greatly increased by either pressing the wood for 10 min. at 2,500 psi or sanding it against a flat surface with fine (600 grit) sandpaper. Microtoming alone was not satisfactory in producing a smooth surface and a high signal/noise ratio. The FTIR-IRS spectrum of oxygen plasma-treated wood indicated a substantial absorbance increase in the 1648–1633 cm^?1 region due to formation of carbonyl groups.     

An Infrared Spectroscopic Study of Chemically Modified Chemithermomechanical Pulp

FT-IR spectroscopy was used to characterize chemically modified wood pulp and to judge the efficiency of different pulp modification processes. Treatment of wood pulp with aliphatic anhydrides was shown to be more effective in a polar solvent such as DMF compared to a non-polar one typified by xylene. The esterification of hydroxyl group associated with the cellulosic material was indicated by the characteristic absorption bands of the resulting cellulosic esters; the degree of hydroxyl conversion was determined by the ratio of peak intensity of hydroxyl and carbonyl stretching vibrations. The so-called “Infrared Acetyl Index” was shown to give a linear correlation with the gravimetrically determined anhydride uptake. Isocyanate modification of wood pulp yielded more complex infrared spectra, because of various secondary reactions of the reactive isocyanate component. Various aromatic isocyanates, used for chemical treatment of the wood pulp, led mainly to urethane formation, as evidenced by the spectra of the modified pulp. The presence of polyurea or urea as the main reaction product of aromatic isocyanates, postulated by a number of authors, could not be confirmed. Nevertheless, phenylisocyanate treatment, at high concentration of isocyanate and without purification of the modified pulp, led to the appearance of at least one more reaction product in the pulp spectra, which is presumed to be either triphenylisocyanurate, the trimerization product of phenylisocyanate, or carbanilide.     

Effect of transition metals addition on the catalyst of manganese/titania for low-temperature selective catalytic reduction of nitric oxide with ammonia

To retard the sintering, a series of transition metals were added to the low-temperature SCR catalysts based on Mn/TiO₂, and activity of these catalysts was investigated. It was found that the transition metal had significant effects on the catalytic activity. With the addition of transition metals, more NO could be removed at lower temperature. The temperature of 90% NO conversion could decrease to 361 K by using Fe(0.1)–Mn(0.4)/TiO₂. The results of X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron diffraction spectra (EDS) indicated that manganese oxides and titania could be better dispersed in the catalyst, and higher catalytic activity was obtained. From X-ray photoelectron spectrum (XPS) it could be known that solid solution was formed among the transition metal, manganese oxides and titania. With the formation of this solid solution, the Brunauer–Emmett–Teller (BET) area and pore volume increased. Furthermore, the in situ diffuse reflectance infrared transform spectroscopy (DRIFT) results showed that by using these catalysts, more NO could be oxidized to NO₂ and nitrate, and then reacted with NH₃. Therefore, the catalytic activity was greatly improved by the addition of transition metals.     

Heat‐damage assessment of carbon‐fiber‐reinforced polymer composites by diffuse reflectance infrared spectroscopy

Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was used to assess the effects of heat damage on carbon‐fiber‐reinforced polymer composites. Moisture‐saturated graphite–epoxy laminates with a quasi‐isotropic lay‐up were heat‐damaged above their upper service temperatures. The loss of matrix‐dominated mechanical properties due to heat exposure was investigated in the laboratory under environmental testing conditions with mechanical tests, ultrasonic C‐scanning, and DRIFT spectroscopy. The reduction of the mechanical strength of the composite materials was accompanied by an increase in the carbonyl band integral and a decrease in the phenyl ratio and hydroxyl and hydrocarbon band integrals, as shown by the DRIFT spectra. DRIFT was confirmed to be more effective than ultrasonic inspection in evaluating the extent of heat damage, and a good correlation was found between the mechanical test results and DRIFT spectra. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1222–1230, 2005     

Composite materials manufactured from wood particles modified through a reactive extrusion process

Wood‐based composites such as particleboard and medium‐density fiberboard are currently made with formaldehyde‐containing adhesives. Since the government is continuously developing and implementing very stringent regulations to eliminate formaldehyde emissions into the environment, alternative approaches must be developed to replace these adhesives. This study examined the concept of using a reactive extrusion process as a means of developing a new, formaldehyde‐free binding system for wood composite products. The surfaces of wood particles were modified by grafting maleated polyolefins through a continuous reactive extrusion process. Chemical changes resulting from this treatment were followed by studying the Fourier transform infrared (FTIR), ¹³C nuclear magnetic resonance (NMR), and X‐ray photoelectron spectroscopy (XPS) spectra. The modified wood particles were compression‐molded into panels, which were tested for mechanical properties. FTIR, ¹³C NMR, and XPS data revealed that the chemical reactions have taken place between the hydroxyl groups of wood particles and maleated polyolefins. The mechanical property test results indicated that the composite panels compared favorably with current standard requirements for conventional particleboard. POLYM. COMPOS., 26:534–541, 2005. © 2005 Society of Plastics Engineers     

Cadmium removal byJuniperus monosperma: The role of calcium oxalate monohydrate structure in bark

This study suggests that calcium oxalate monohydrate overJuniperus monosperma bark is an ion-exchangeable site for cadmium adsorption on the basis of its cadmium adsorption behavior and surface characterization. Cadmium adsorption behavior showed that juniper bark had a higher cadmium adsorption capacity (84.6 Μmol Cd g^-1 at pH 5) than juniper wood (32.0 Μmol Cd g⁻¹ at pH 5), and that the base-treatment improved the cadmium adsorption capacity of only juniper wood. This difference between juniper bark and wood might have originated from different cadmium binding sites. In calcium displacement, the cadmium uptake onto juniper bark was identical to the amount of calcium ions displaced, which indicated that calcium played an important role in cadmium adsorption onto juniper bark. X-ray diffraction (XRD) results gave evidence that only juniper bark contained the structure of calcium oxalate monohydrate. Furthermore, cadmium adsorption decreased the intensity of the characteristic XRD peaks for calcium oxalate monohydrate. In diffuse reflectance infrared Fourier transform (DRIFT) spectra, existence of oxalate on juniper bark was proven again and interpretation on IR band of carbonyl groups matched significantly the cadmium adsorption behavior.     

FT‐IR microscopic studies on coupling agents: treated natural fibres

Natural fibres (sisal) were treated with various coupling agents such as organosilane, zirconate, titanate and N‐substituted methacrylamide. The nature of the adsorbed chemical species on the fibre surfaces was analysed by Fourier transform infrared microscopy (FT‐IR). The presence of precipitated oligomers on the surface was confirmed by the appearance of hydrogen‐bonded carbonyl group and unsaturation bands. The results showed an irregular physisorption/chemisorption of coupling agents, their penetration beyond the surface, and a decrease in the hydrophilicity of fibres. SEM and dynamic contact angle studies on the fibres supported these findings. FT‐IR microscopy in its reflectance mode was more effective in ascertaining the chemical nature and structure of adsorbed layers onto sisal fibre surfaces compared with DRIFT and transmission spectroscopy. The difference in the properties of untreated and chemically treated fibres has also been verified in the polymer composites. © 2000 Society of Chemical Industry     

Study on the preparation and mechanical properties of injection‐moulded wood‐based plastics

The objectives of this study were to prepare injection‐moulded wood‐based plastics and to characterize their mechanical properties. Injection‐moulded wood‐based plastics with satisfactory flexural (65.7 MPa) and tensile strengths (30.1 MPa) were successfully obtained through a simple reaction of mulberry branch meal with phthalic anhydride (PA) in 1‐methylimidazole under mild condition. The X‐ ray diffraction results indicated complete disruption of the crystallinity of cellulose because the pattern obtained for esterified fiber was almost a straight line without any peaks. The peaks in the Fourier transform infrared spectroscopy spectra (1738 and 748 cm^?1) and NMR spectra (173.3 and 133.5 ppm) indicated the attachment of 0‐carboxybenzoyl groups onto the wood fibers via ester bonds. The differential scanning calorimetry curves showed that the glass transition temperature decreased with increasing weight percentage gain (WPG). The derivative thermogravimetric analysis curves indicated that esterified wood fiber was less thermally stable than the untreated fiber and that the component tends to be homogeneous with increasing WPG. Scanning electron microscope revealed that the fractured surfaces of most samples were smooth and uniform but that high temperature and less PA dosage could lead to the appearance of holes and cracks. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41376.     

Mechanism of smoke suppression by melamine in rigid polyurethane foam

The smoke suppression of rigid polyurethane foam (RPUF) modified by melamine was investigated based on three sections: the condensed phase, the carbon layer, and the gas phase. In the condensed phase, the results of thermogravimetry, X‐ray photoelectron spectroscopy (XPS) N1S spectrum, and Fourier transform infrared spectroscopy indicated that melamine could suppress the degradation of RPUF by reacting with the aromatic hydrocarbons. It also reduced the smoke generation because the volatilizable aromatic hydrocarbons were the principal smoke precursors in a fire. In the carbon layer, the decrease from 38.50% to 24.76% of the inner layer oxygen content identified by XPS full‐spectrum and C1S spectrum indicated that melamine could prevent oxygen from transferring into the inner foam by the formation of an enhanced surface carbon layer, and the enhanced carbon layer could also block the release of smoke precursors. In the gas phase, the content of total aromatic hydrocarbons declined to 59.12% according to pyrolysis gaseous chromatography mass spectroscopy and indicated that melamine could reduce the smoke precursors. The results of smoke density chamber and cone calorimeter tests revealed that the addition of the melamine could decrease the smoke density of burning RPUF. Copyright © 2014 John Wiley & Sons, Ltd.     

Photostability of wood surfaces esterified by benzoyl chloride

The photostabilization of wood surfaces is desirable to enhance the life of wood under exterior use and to improve the performance of clear coatings on wood surfaces. Chemical modification of wood has been found effective in upgrading properties such as biological durability and dimensional stability and has been suggested as a potential way for inducing photostability on wood surfaces. In this study, the photostability of chemically modified wood was assessed under accelerated weathering conditions. Wood specimens of Pinus roxburghii (Chir pine) were esterified with benzoyl chloride to 19.5 wt % gain and exposed to a xenon arc light source in a Weather‐O‐Meter for different periods ranging from 0 to 500 h. The irradiated samples were analyzed for color changes and chemical changes. The analysis of color changes in wood surfaces by ultraviolet–visible irradiation was carried out with a color measuring (CIELAB) system, and chemical changes were characterized with fluorescence and Fourier transform infrared spectroscopy. The esterification of wood by benzoyl chloride suppressed the color changes (photodiscoloration) due to irradiation. Modification also reduced the lignin degradation and generation of carbonyl groups on the surface of the irradiated wood. The fluorescence emission spectra of irradiated unmodified wood showed a large reduction in intensity and a large redshift in the emission maximum, whereas modified wood showed only a small change in fluorescence intensity on irradiation. The results show that the esterification of wood with benzoyl chloride was effective for the photostabilization of the wood polymers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Microautoradiographic studies of the penetration of alkyd, alkyd emulsion and linseed oil coatings into wood

The penetration of wood coating primer products into pine and spruce softwood was evaluated with microautoradiography.¹⁴C-labeled binders of alkyd and linseed oil were synthesized and used in eight different products. The penetration front in wood is uneven due to a heterogeneous structure with different types of wood cells. It was demonstrated that conventional solventborne alkyd primers and waterborne alkyd emulsion primers have similar ability to penetrate into wood. Improved penetration was found for products with lower viscosity, such as an alkyd stain and a linseed oil coating. A priming oil had superior penetration. Generally better penetration was obtained for coatings applied onto sawn and rough surfaces as compared to planed and smooth surfaces. Box 5609, S-11486 Stockholm, Sweden. P.O. Box 160, 2001 Lillestr?m, Norway. Box 5607, S-11486 Stockholm, Sweden.     

IR spectroscopy of coal 1. Difference in DRIFT spectra of coal in repeated measurements

For coal powder, log-scaled DRIFT spectra correspond to quantitative measurements. Among the repeated (parallel) spectra of a single sample, the best is the spectrum with maximum reflection in the transparency region. It is incorrect to average parallel spectra.     

Hydrothermal Liquefaction of Cypress: Effect of Water Amount on Structural Characteristics of the Solid Residue

Hydrothermal liquefaction of cypress was performed in an autoclave with various amounts of water. The obtained acid‐soluble and acid‐insoluble solid residues were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, sugar analysis, elemental analysis, and nuclear magnetic resonance to help understand the reaction mechanisms of this process. The characteristics of solid residues were significantly affected by the water amount. Cellulose was more stable at high water amount and hemicelluloses were much more reactive than cellulose. Comparison of nuclear magnetic resonance spectra of milled wood lignin and milled solid residues indicated a significant cleavage of the side chains. The components of milled solid residues were mainly derived from decomposition and repolymerization of lignin. The decomposition of the side chains was substantial for lignin depolymerization during hydrothermal liquefaction.     

Surface of cellulosic materials modified with functionalized polyethylene coupling agents

The interfacial adhesion between a wood fiber and a plastic matrix strongly influences the performance of wood‐fiber‐reinforced thermoplastic composites. Fiber surface modification with coupling agents is generally needed to induce bond formation between the fiber and polymer matrix. This study investigated the chemical reactions between cellulosic materials and functionalized polyethylene coupling agents. Both wood flour and cotton cellulose powder were treated with acrylic acid‐functionalized polyethylene and maleic anhydride‐functionalized polyethylene (maleated polyethylene) for surface modifications, and chemical changes resulting from these treatments were followed by a study of the Fourier transform infrared and X‐ray photoelectron spectroscopy spectra. Variations in the band intensities, oxygen‐to‐carbon ratios, and concentrations of unoxidized carbon atoms were related to changes that occurred on the surfaces of modified cellulosic materials. The experimental results indicated that chemical bonds between the hydroxyl groups of the cellulosic materials and the functional groups of the coupling agents occurred through esterification reactions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 278–286, 2003     

The surface energy spectrum of PVC

A new theory enabling the surface energy of a solid to be expressed as a quantitative energy spectrum has recently been proposed. This theory was tested on clean and contaminated polyvinyl chloride (PVC) surfaces which yielded remarkably different spectra. Electron spectroscopy for chemical analysis (ESCA) confirmed that peak energies could be correlated with specific molecular groups exposed at the surface.     

Effects of Solvation and Ionization on 13C NMR Spectra of Lignin Model Compounds,Spruce Milled Wood Lignin and Kraft Lignin

The effects of alkali and polar aprotic solvent on the aromatic carbons signals in ¹³C NMR (Carbon-13 nuclear magnetic resonance) spectra of lignin model compounds and spruce milled wood lignin (MWL) were studied. It was found that in 1 M aqueous NaOH signal shifts of C-1 and C-4 carbon atoms in the aromatic ring were the most noticeable in lignin models with free phenolic hydroxyl groups, which are ionized under the conditions. A similar effect in the spectra of the studied model compounds was observed in 0.5 M aqueous NaOD-deuterated dimethyl sulfoxide (DMSO) mixture (DMSO: water ratio 3:7 v/v). The model data help explaining changes in the ¹³C NMR spectra of MWL and lignin in situ dissolved in spruce kraft black liquor caused by ionization. In the ¹³C NMR spectra of spruce black liquor the signals of phenolic and non-phenolic lignin units are clearly separated and do not overlap with the signals of the carbon atoms of carbohydrates and other aliphatic products of wood degradation. The data obtained are useful in understanding the important role of solvation and ionization processes leading to lignin solubilization.