Infrared spectra of jute stick treated with white-rot fungus

Jute stick was treated with white-rot fungus for incubation periods of 6 days (MBA) and 12 days (MBB). The infrared spectra of fungus treated samples (MBA and MBB) and control jute stick (MBC) were analyzed and compared. The bands attributed mainly to hemicellulose show an increase in absorbance intensity ratios (A_ν/A₂₉₀₀) with increase of incubation time. Similarly the bands attributed to lignin show an increase in the absorbance intensity ratios with increase of incubation time. Increase in the intensity of 1635 cm^?1 band with increase of incubation time was also observed.     

Infrared spectra of jute stick and alkali-treated jute stick

Defatted jute stick was treated with sodium hydroxide solution (2% w/v) at ambient temperature (～ 32～C) and boiling water bath temperature (95–97°C). Infrared (IR) spectra of defatted jute stick and alkali-treated jute stick were studied. The IR spectra of the alkalitreated jute stick were conspicuous by the absence of the 1730 cm^?1 band, as compared to that of jute stick. Another characteristic feature of the alkali treated jute sticks is the absence of the band at 1240 cm^?1, which is replaced by the 1265 and 1225 cm^?1 bands; other bands in the above samples also recorded significant changes.     

Infrared Absorption Spectra of Cellulose Pulps of Palm Tree

Palm leaves are used for the production of different cellulose pulps; their properties are investigated, the resulting pulps were bleached by a multistage process, the effects of the addition of solvent during the pulping process on the chemical structure of the pulps are discussed. The strength properties of the paper which is produced from unbleached and bleached pulps increased with increasing cellulose percentage and decreasing lignin content in the pulp. Infrared absorption spectra were recorded for different unbleached and bleached pulp in the frequency range 200–4000 cm^-1 by using the alkali halide disk technique; the factors which affect the experimental technique were calibrated through these studies. The structural units within pulping yield (holocellulose, hemicellulose, cellulose, lignin, and ash) were interpreted within the pulp network structure by the infrared absorption spectra, where different samples of unbleached, bleached soda, and kraft pulps were also elucidated by IR spectra, after preheating at different temperatures and with using different ratios of organic solvents. The addition of organic solvents decreased or increased the crystallinity indices, depending on the type of solvent and the pulping temperature. It was also found that, at the same pulping temperature (155°C) and with the same percent of organic solvents in the pulping liquor, the asymmetry indices also the mean hydrogen bonding strength (A _OH/A_CH) of the unbleached soda pulps (organosolv or nonorganosolv pulping) were less than that of unbleached kraft pulps, except for the pulps obtained by pulping with dioxan at 155°C. The mean hydrogen bond strength of the bleached pulps decreased or increased, depending on the type solvent used and the pulping temperature.     

Polyacrylonitrile (PAN)-grafted jute fibres: Some physical and chemical properties and morphology

Grafting of polyacrylonitrile (PAN) on (dewaxed and bleached) jute fibres was done by aqueous polymerization of acrylonitrile (AN) in the presence of the fiber samples employing a sodium periodate (IO₄^?) and copper sulfate (Cu²⁺) combination as the initiator. Effect of PAN grafting to different extents on X-ray crystallinity, tensile properties, thermal behavior, whiteness index, dyeability, light-fastness rating, and moisture regain properties of the fiber samples were studied and analyzed. Their rot resistance, determined by a standard soil burial test, were also examined and compared. Twenty to thirty percent PAN-grafting was found to impart a most desirable balance of physical properties including fiber strength and modulus, moisture regain, whiteness index, and light-fastness rating. PAN grafting also makes the otherwise nonresistant jute fiber significantly rot-resistant. Morphology of the different fiber samples as studied and compared using scanning electron microscopy indicates that PAN grafting occurs on surfaces and intercellular regions as well as within the lumens of the multicellular jute fibers. © 1994 John Wiley & Sons, Inc.     

Graft copolymerization of acrylonitrile onto jute fibers (studies on Ce(IV)-hippuric acid redox system)

Graft copolymerization of acrylonitrile (AN) onto chemically modified bleached jute fibers was studied using Ce(IV)-hippuric acid redox initiator system. The effects of time, temperature, concentration of monomer (AN), metal ion (Ce⁴⁺), hippuric acid, sulfuric acid, and amount of jute fiber on graft yield have been studied. The effects of some organic solvents and inorganic salts on graft yield have also been studied. Infrared spectra of chemically modified bleached jute and grafted jute have been taken and their characteristic bands have been identified. More than 90% graft yield could be achieved with the present system.     

Graft copolymerization of nitrile monomers onto bleached jute fiber using potassium persulfate system and their textile characteristics

Graft copolymerization of nitrile monomers, such as acrylonitrile and methacrylonitrile, onto bleached jute fiber was carried out by using K₂S₂O₈/FeSO₄ redox system in nitrogen atmosphere and their effect on the textile characteristics was also investigated. Percent graft yield increased with the increase of concentrations of monomer, initiator, and catalyst, reaction time, and reaction temperature up to a certain value, and, thereafter, it decreased. The effect of percent grafting efficiency was similar to that of percent graft yield, except for the monomer concentration. The increase of percent graft yield was dependent on the availability of jute‐macroradicals as well as monomer radicals. Sometimes the predominancy of homopolymerization over grafting and the premature termination of growing grafted chains occurred because of the higher monomer radicals and excess primary radicals, SO₄^?? and ^?OH, from K₂S₂O₈ initiator. The percent graft yield of acrylonitrile and methacrylonitrile was 20.5 and 29.1%, respectively. Higher graft yield for methacrylonitrile might be due to the methyl group present in it. Infrared spectra at 2229–2235 cm^?1 of acrylonitrile‐ and methacrylonitrile‐grafted jute strongly supported the graft formation. Grafting of jute fiber improved the thermal stability, protected from photooxidative degradation, and decreased swellability as well as dyeability, etc. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3622–3629, 2004     

Studies on graft copolymerization of acrylonitrile onto jute fiber with permanganate ion initiation system in presence of air

The graft copolymerization of acrylonitrile with jute using potassium permanganate as the initiator has been studied in the presence of air. To establish reaction conditions for the graft copolymerization of acrylonitrile (AN) onto jute, the effect of different variables such as the residual lignin content of bleached jute (after bleaching with sodium chlorite), initiator concentration, monomer concentration, time of polymerization, reaction temperature, and amount of bleached jute fiber have been studied. As evidence of polymer grafting, some instrumental analyses such as scanning electron microscopy, infrared, and thermogravimetry have been carried out. The extent of grafting of acrylonitrile depends on how much lignin is present on the jute fiber. Percent grafting and grafting efficiency have also been studied. © 1995 John Wiley & Sons, Inc.     

Preparation,characterization, and properties of unbleached,bleached, and grafted pulps from JRC‐321 variety jute fiber

Graft copolymerization onto jute pulps opened the door to new concepts in pulp and paper research. Jute pulp from the JRC‐321 variety white jute fiber was prepared by the alkaline sulfite pulping process. The pulp obtained was bleached by the chlorination, extraction, and hypochlorite sequence technique to remove excess lignin for making bright and good quality paper. Special attention was focused on the graft copolymerization of acrylamide monomer onto the unbleached and bleached pulps by the use of a complex initiating system: Cu(II)/glycine/KHSO₅ in aqueous solution. It was found that percentage grafting was high in the case of bleached pulp. The grafted pulps so obtained were characterized by FTIR and their thermal behavior was characterized by TGA. Their mechanical properties such as tensile strength, percentage elongation, and tenacity were measured and compared. The physical properties such as rot‐resistance and water‐retention capacity of the grafted and the ungrafted pulps were determined. The effect of the percentage grafting variation on the above mentioned properties was examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1963–1969, 2002     

Graft copolymerization of styrene,methylmethacrylate, and acrylonitrile onto jute fibres

The contribution of jute constituents, namely, water soluble matters, waxes, pectins, lignin, hemicelluloses, and α-cellulose in the graft copolymerization reaction of jute fabric with some vinyl monomers was investigated. Styrene, methylmethacrylate, and acrylonitrile were used as the monomers and Fe²⁺/H₂O₂ redox system as initiator. The graft copolymerization reaction was carried out at 80°C using different concentrations of monomer and initiator for different lengths of time. The water soluble matters, pectins, and lignin were found to accelerate the graft copolymerization reaction during the initial stages of the reaction and in the meantime impede termination during the latter stages of the reaction. Generally, the magnitude of grafting is governed by nature of the substrate, nature of the monomer, and the conditions of the polymerization reaction. Grafting decreases the moisture regain of jute and substrates derived thereof irrespective of the monomer used within the range studied. Also, grafting decreases the tensile strength and imparts rot-proofing properties to the substrates examined.     

Weathering performance of spruce coated with water based acrylic paint modified with TiO2 and clay nanoparticles

This work examines the effect of wood specimens coated with water based acrylic coatings modified with TiO₂ and clay nanoparticles against weathering strain. The long-term durability of the specimens towards climate strain was studied within a relatively short time frame by accelerated climate ageing. The surface changes that occurred as a result of photodegradation of the specimens subjected to accelerated climate exposures were studied using colour measurements and Fourier transform infrared (FTIR) spectroscopy. The results revealed a significant decrease in the intensity of lignin bands attributed to degradation of the lignin component of the wood. However, the intensity of the lignin photodegradation was lower for coated specimens, with slightly lower degradation for the specimens coated with paints modified with TiO₂ and unmodified montmorillonite clay nanoparticles.     

Evaluation of the contribution of lignin stilbene phenol units in the photoyellowing of peroxide-bleached lignin-rich pulps

In order to assess and quantify the contribution of stilbene phenols in photoreversion of bleached high-yield pulps, a method to reduce the stilbene double bond and quantify the formed diphenylethane was developed on 4-benzyloxy-3,3′-dimethoxy-4′-hydroxystilbene, as lignin monomer model, and also on a more sophisticated lignin polymer model constituted by a polystyrene framework containing 4,4′-dihydroxy-3,3′-dimethoxystilbene elements as pendent groups. The method used RhCl(PPh₃)₃ as soluble catalyst to get an efficient hydrogenation and AlCl₃ in benzene to liberate the diphenylethane from the polymer framework. For the first time a semiquantitative evaluation of the content of the stilbene phenols formed from β-1 units was given for high-yield pulps. The value of 2 p-stilbene phenols for 1000 C₉ lignin units found indicates that they are present in very small quantities after the peroxide bleaching. UV irradiation of the polystyrene model adsorbed on solid cellulose matrix had revealed an efficient stabilization after the hydrogenation treatment. This was not the case for the peroxide bleached pulp showing that the p-stilbene phenols formed from β-1 units are not the main contributors of the rapid yellowing of bleached lignin-rich pulps. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2517–2531, 1998     

Molecular orbital study of pyrolytic carbons based on small cluster models

Molecular orbital calculations are applied to the Raman scattering and ESR of pyrolytic carbons on the basis of small cluster models. The E_2g and A_1g modes of C-C stretching vibrations of coronene, hexabenzocoronene, and circumcoronene, which belong to D_6h carbon clusters, are shown to appear around the 1550 cm⁻¹ and 1360 cm⁻¹ bands, respectively. The unpaired electrons observed in pyrolytic carbons are attributed to the bond-alternation defects on odd-numbered carbon clusters that are more easily mobile than those of trans-polyacetylene.     

CO hydrogenation over supported cobalt catalysts: FTIR and gravimetric studies

The hydrogenation of CO over supported cobalt catalysts has been studied using in situ FTIR spectroscopy and gravimetry at P = 6 bar, T = 473–723 K and H₂/CO = 2–3. On both silica- and alumina-supported catalysts IR absorption bands corresponding to linearly adsorbed CO on metallic cobalt were observed. On alumina an additional pair of bands at lower frequencies was attributed to bridge-bonded CO. Absorption bands corresponding to adsorbed hydrocarbons (3050–2700 cm^?1) and to oxygen containing species (1800–1200 cm^?1) were found to correspond to adsorbed products or unreactive species. The gravimetric studies showed a significant difference between the supports. On the silica-supported catalyst the weight uptake decreased with increasing temperature (473–573 K). The weight increase during reaction was attributed to adsorbed hydrocarbon reaction products. On the alumina-supported catalyst the weight uptake increased with increasing temperature, and there was also a significant weight increase with the support alone. Most of the weight uptake can be attributed to the formation of stable formate and carbonate species on the alumina support. At 723 K the deposits formed were stable in H₂, and the shape of the curves indicated different mechanisms for deposition of material. In particular the Co/Al₂O₃ sample showed a very high and linear rate of weight gain, which was an order of magnitude higher than for the other samples.     

Chemical modification of jute fibers. II: A study on the Fe2+/H2O2-initiated graft copolymerization of methyl methacrylate,acrylonitrile, and acrylamide onto jute fibers

The study of graft copolymerization of methyl methacrylate, acrylonitrile, and acrylamide onto both defatted and bleached jute fibers using the ferrous ammonium sulfate / H₂O₂ redox initiator system has been made. To determine the optimum conditions of grafting, the effects of concentrations of ferrous ammonium sulfate, monomer, H₂O₂; time and temperature on percentage of graft yield have been studied. Acrylamide was found to graft onto the fiber only at a fixed ferrous ammonium ion concentration (5 × 10^?4M). Kinetic studies showed that the rates of grafting follow the second-order mechanism. The activation energies of the reactions were found to be 3.351 and 2.53 kcal/mol in the methyl methacrylate and acrylonitrile systems, respectively. The grafted fibers have been characterized by thermogravimetric analysis, IR spectroscopy, and XRD studies.     

Diffusion behavior of poly(ethylene imine) into keratin fibers using microspectrophotometry

In order to investigate the diffusion behavior of poly(ethylene imine) (PEI) into keratin fibers, cross‐sectional samples of bleached white human hair treated with PEI were prepared. We were successful in developing a method for analyzing the diffusion behavior of PEI into human hair, which to our knowledge is a first. The diffusion pattern of PEI into human hair, which cannot be determined by optical microscopy, can be determined by our method. After the treatment, the cross‐sectioned hair samples were dyed with Orange II and the cross‐sectional intensity scans were measured at a wavelength of 487 nm (λ_max of Orange II) with a microspectrophotometer. In our method, the diffusion pattern of PEI at pH 11.1 showed Fickian type characteristics. This suggests that the diffusion coefficient of PEI is essentially independent of the PEI concentration. By calculating the diffusion coefficient from the PEI concentration profile, the diffusion coefficient of PEI [number‐average molecular weight (M_n) = 300 and 600] into the bleached human hair was found to be on the order of 10^?10 cm²/s. In addition, the diffusion coefficient of PEI (M_n = 600) with urea added increased twofold in comparison with that of PEI without urea added. This experiment demonstrated that urea acts as a penetration accelerator for PEI. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 65–71, 2005     

Self‐doping of polyaniline prepared with the FeCl3/H2O2 system and the origin of the Raman band of emeraldine salt at around 1375 cm−1

Stepwise addition of H₂O₂ in small portions into the polymerization mixture reduces the number of defects in polyaniline (PANI) prepared with the Fe³⁺/H₂O₂ system, although it does not eliminate them completely. PANIs slightly self‐doped with phenolic groups are thus obtained, which show conductivity from 2.65 to 0.38 S cm^?1 as the total H₂O₂/aniline mole ratio is increased from 0.125 to 1.25. The conductivity shows a good correlation with the A_B/A₉₀₀ UV?visible absorbance ratio of the PANI emeraldine salt form (PANI ES), much better than with the A_B/A_Q ratio of the corresponding emeraldine base form. This corresponds well with the assignment of the band at 900 nm to polaronic transitions. Partial self‐doping of PANIs with weakly acidic phenolic groups allowed evidence to be obtained for the assignment of Raman bands at 1370 cm^?1 and 734 cm^?1 (for λ_exc = 780 nm) to vibrational modes of highly localized polarons. The presence of the band at 880 cm^?1 in the IR spectra of these PANI ES samples that are totally free of sulfate ions proves that this band is associated with a vibrational mode of PANI ES and need not be assigned to a mode of HSO₄^? ions, as has been suggested by some authors. © 2015 Society of Chemical Industry     

Optical temperature sensing and luminescent switching properties in Pr/Er-doped (K0.5Na0.5)NbO3 materials

For optical temperature sensing materials, the emission and excitation bands are extremely critical to measure the temperature by fluorescence intensity ratio (FIR) technique. Singly Ln-doped optical temperature sensing materials exhibit very few emission bands, which greatly constraints their practical applications of FIR technique. Here, the fabricated Pr/Er co-doped (K_0.5Na_0.5)NbO₃ materials exhibited multi-color (red-green) and dual-mode (downshifting/upconversion) luminescence properties. The temperature sensitivity can be effectively tuned by choosing different emission or excitation bands. The optimized optical temperature sensitivity reached up to 0.0094 K⁻¹, much higher than that of most temperature sensing materials. Besides, the samples also showed excellent luminescence modulation properties based on the photochromic reaction. Under sunlight irradiation, the luminescent switching contrast (ΔR_t) of the samples reached more than 60%. These results may provide a guiding role in designing and modulating optical temperature sensing properties for multifunctional materials.     

Physicochemical properties of hydrolyzed and blended chitin

The molecular structures of chitin and chitin hydrolyzed with sodium hydroxide for different time intervals at 160°C were followed using infrared spectroscopy in the range 200–4000 cm^?1. The frequency and intensity of active groups NHCOCH₃, NH₂, OH, and OCH₃ in chitin, chitosan, cellulose, and lignin, respectively, were calculated and correlated with molecular structural changes. The dielectric constant ?′, dielectric loss ?″, and dissipation factor tan δ for the investigated samples were measured in the frequency range 0.1–100 kHz and interpreted in terms of the molecular structure elucidated from the infrared spectroscopic studies. Also, the effect of blending of cellulose and lignin with chitin on their dielectric properties was investigated. It was found that hydrolysis of chitin improved its insulating properties.     

Structural and Photoluminescence Study of Eu3+/TiO2 Xerogels as a Function of the Temperature Using Optical Techniques

Eu³⁺/TiO₂ xerogels have been obtained from colloidal sols by drying at room conditions. Anatase with traces of brookite phases are obtained from the synthesis and the stability of both with temperature is higher (from 400°C up to 800°C) when Eu³⁺ is present. Raman phonons have been used to detect the different phases and follow the structural transitions. The observed changes with calcination temperature of anatase modes (E_g,1, B_1g,₁ A_g/B_1g,2, and E_g,3) are found to be mainly related to the grain size. The anatase grain size increases more and at lower temperatures for undoped than for Eu³⁺‐doped samples favoring the transition to rutile. The stability of the brookite phase is also influenced by the doping being higher in the doped xerogels (700°C) than in the undoped ones (400°C). No concentration quenching of the f–f Eu³⁺ emission bands is observed up to 3% Eu³⁺ at low temperatures but the maximum emission is found at lower temperatures for higher Eu³⁺ content may be due to quenching related to Eu³⁺ migration. The narrower f–f emission bands of the as‐prepared samples are consistent with the presence of Eu³⁺ ions at the surface with a weak interaction with the TiO₂ nanoparticles. A diffusion process of Eu³⁺ ions occurs during calcination from the surface to different positions of the anatase lattice close to the surface producing an inhomogeneous broadening. Finally, the formation of the pyrochlore phase Eu₂Ti₂O₇ is detected which explains the decrease on the emission efficiency and the increase of the Eu³⁺ environment symmetry.     

Phosphorylated cation‐exchangers from cotton stalks and their constituents

Cation‐exchangers were prepared by phosphorylation of cotton stalks and their isolated constituents (lignin, soda‐anthraquinone pulp, and bleached cellulose pulp). FTIR spectra of the phosphorylated materials showed new absorption bands at 950–1200 cm^?1 of the C? O? P bonds as a result of phosphorylation. The adsorption of different heavy metal ions (lead, copper, nickel, cobalt, chromium, and cadmium) at different metal ion concentrations (50–1500 μg) by the phosphorylated cotton stalks was studied. The adsorption of metal ions by the phosphorylated cotton stalks increased by increasing their concentration. The binding capacity of phosphorylated cellulose, lignin, and soda‐anthraquinone pulp was measured at 1000 μg metal ion concentration. The adsorption of the different heavy metal ions by phosphorylated‐lignin and ‐bleached cellulose pulp was higher than that of phosphorylated cotton stalks. Thermogravimetric analysis of the raw and phosphorylated cotton stalks showed that the resistance of the phosphorylated cotton stalks to thermal degradation was higher than that of raw cotton stalks (lower rate of weight loss), despite the lower degradation onset temperature of the phosphorylated cotton stalks. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2950–2956, 2003