Enzymatic conversion of irradiated cellulosic materials

Initial rate and degree of conversion in enzymatic hydrolysis of cellulosic materials (CM—cotton linter and bagasse) have complicated dependencies on dosage of γ-irradiation. The decrease in reactivity at low doses is explained by a decrease in the CM surface caused by radiation-induced crosslinkages. Doses higher than 0·5 MGy increased reactivity; at 2 MGy the degree of conversion (48 h hydrolysis) was about 5 times higher than in controls. Increased reactivity was caused by depolymerization, increased solubility and decrease of crystallinity index of CM.     

植物纤维素原料的生物转化与利用

采用生物技术对植物纤维原料进行转化利用,是一项具有重要意义的研究工作。本文简要介绍了纤维素酶的生产、利用纤维素原料生产酒精、乳酸、2,3-丁二醇及木糖醇等方面的研究进展。     

Cerium-initiated grafting of acrylonitrile onto cellulosic materials

Grafting of acrylonitrile onto native cotton, swollen cotton, viscose, ramie, and hydrocellulose was studied with tetravalent cerium as initiator. The effect of temperature on the graft yields is examined. With ceric ammonium nitrate the grafting yields are found to be higher at 20 and 40 than at 60°C. Ceric ammonium sulfate, on the other hand, produces more grafting at 60 than at 20 and 40°C. The consumption of ceric ions is less, whereas the per cent graft yields are higher for the swollen cottons and viscose than for native cotton. Graft yields are shown to be related to substrate accessibility if the grafting reaction is carried out under conditions that suppress homopolymerization. Oxidation of these celluloses with Ce^IV has also been studied. It is found that more Ce^IV is consumed during grafting than during oxidation of cellulose under identical reaction conditions. Excess Ce^IV consumed in the grafting reaction has been shown to be directly related to extent of homopolymerization, which accompanies grafting. Some data on the storage stability of the free-radical activity produced by oxidation of cellulose with Ce^IV are also reported. It is observed that the cerium-oxidized samples can initiate graft poly merization even after 4–5 hr. if stored in nitrogen.     

Developments in direct dyes for cellulosic materials

Single crystal data and the X-ray powder pattern are reported for CI Solvent Yellow 2 (l-phenylazo-4-NN-dimethylamine). The powder pattern has been indexed from cell dimensions given by single crystal measurements. The problems of multiple indexing have been reduced by comparing the powder data with observed single crystal intensities.     

Biomordanting willow bark dye on cellulosic materials

A semi‐quantitative study of willow bark dye adsorption on two different cellulose materials using biomordants was carried out. The studied celluloses were microcrystalline cellulose (MCC) AaltoCell and regenerated Ioncell‐F (IC) fibres. The dye was a hot water extract of willow bark and the adsorption to cellulose was carried out using carboxylic acid‐containing biomordants, namely, oxalic acid, citric acid and tannic acid. Alum was employed as the reference mordant. A semi‐quantitative estimation of the dye uptake was conducted using high‐performance liquid chromatography equipped with a diode array detector and also by visual inspection, as well as an evaluation of the coloration using CIELab parameters. The mechanism of the dye adsorption on the cellulose surfaces was studied via Fourier Transform–infrared spectroscopy. According to the results, MCC had a higher affinity for polyphenolic dye than the regenerated cellulose fibres. Dye uptake on MCC was 50%‐80% and 44%‐57% on IC. For MCC, the biomordants improved the dye uptake more effectively than the control mordant, alum, whereas for IC the biomordants were less effective than alum.     

Ignition and flash-fire studies of cellulosic materials

Various celloulosic materials were evaluated for ignitability and flash-fire propensity, using screening test methods developed at the University of San Francisco. Time to ignition, using radiation from a high-temperature radiant source without a pilot flame, appeared to be primarily a function of heat flux and material density, rather than of type of wood or celloulosic board. At heat flux levels from 5.8 to 10.5 W cm^?2, time to ignition was shortest for cellulose fiberboard with a density of 0.2225 g ml^?1, followed by western red cedar at 0.314 g ml^?1, eastern white pine at 0.348 g ml^?1, southern yellow pine at 0.422 g ml^?1, Douglas fir at 0.565 g ml ^?1, and longest for hardboard at 0.878 g ml^?1. For the cotton and rayon woven-pile upholstery fabrics, time to ignition appeared to increase with increasing fabric weight. For Cellulose insulation treated with boron-containing additives, flash-fire magnitude decreased with increasing additive content. Flash-fire magnitude decreased more that could be accounted for by decreasing weight loss alone, indication reduction in the combustibility of the volatiles produced. Reduction in flash-fire propensity of cotton bating by treatment with boron-containing additives was also observed.     

Metal ion removal by dyed cellulosic materials

Further studies on adsorption of different metal ions by the four dyed and undyed cellulosic substrates namely cotton fibers, bleached bamboo pulp, jute fibers, and sawdust were carried out. Different metal ions adsorbed were Fe²⁺, Fe³⁺, Pb²⁺, and Hg²⁺. The equilibrium metal adsorption was studied by EDTA method. The control and dyed substrates adsorbed these metal ions to a significant extent, thus providing an effective and cheap method for adsorption of costly but polluting and toxic metals like Pb²⁺ and Hg²⁺. The adsorption levels varied up to 95% for various substrate–dye–metal ion combinations.     

Graft copolymerization of vinyl monomers on cellulosic materials

Graft copolymers of acrylonitrile, ethyl acrylate, methyl acrylate, ethyl methacrylate and methyl methacrylate and of acrylonitrile/ethyl methacrylate and acrylonitrile/methyl methacrylate monomer mixtures on carboxymethylcellulose (degree of substitution 0.4–0.5) were prepared by use of ceric ion initiator in aqueous medium. The extent of graft polymer formation was measured in terms of graft level, molecular weight of grafted polymer chains and frequency of grafting as function of ceric ion concentration. It was found that at comparable reaction conditions, the molecular weight and frequency of grafting were not of the same order of magnitude. For the monomer mixtures, the copolymer compositions obtained from the total nitrogen content of the acrylonitrile/alkyl methacrylate copolymer samples showed that a relativity low amount of the acrylonitrile monomeric units were incorporated into the graft copolymer even at high acrylonitrile content of the feed.     

Sorption of water vapor by various cellulosic materials

Conclusions The form of the dependence between the values of the water surface and the heat of wetting in processes of water vapor sorption by various cellulosic materials has been refined.The connection of water and thermal effects with the degree of crystallinity of cellulosic materials has been shown.Translated from Khimicheskie Volokna, No. 4, pp. 28–29, July–August, 1983.     

Kinetic studies on the accelerated aging of cellulosic materials

The natural aging of cellulosic materials (high purity paper, cotton, raw and bleached flax, viscose) was simulated by thermal oxidation in air at constant temperature (123–192°C). Also the synergetic effect of light was investigated at 50–85°C. The kinetics of polymer degradation was followed through intrinsic viscosity measurements and was correlated with the degree of crystallinity, determined by X-ray diffraction, and with the surface oxidation of the investigated samples, evaluated through XPS analysis. At least two constant rate stages were observed in kinetic runs. The acceleration factors and time necessary for simulating a 20-year thermal aging of the investigated cellulosic materials were obtained from the calculated activation parameters by extrapolation of the process rate coefficients to room temperature. Surface oxidation parallel to aging led to the formation of low-molecular-weight, easily removable products in pure cellulose materials, while in lignin-containing materials mainly lignin was involved.     

Molecular structure and ion exchange of amidoximated cellulosic materials

Modification of lignocellulosic materials, e.g., cotton stalks, bagasse, and rice straw, by incorporation of amidoxime group for ion exchange is investigated. The uptake of metal ions Cu, Cr, Ni, and Fe by these modified lignocellulosic materials is measured. Amidoximated bagasse has higher efficiency toward metal ions uptake than amidoximated cotton and rice straw. The effect of different variables, e.g., metal ion concentration, temperature of metal ion solution, and time of steeping, on the efficiency of the amidoximated (bagasse raw material, unbleached bagasse, and bleached bagasse) ion exchangers toward metal ions uptake is tested. The molecular structure of the prepared amidoxime from bagasse and its pulps is studied by using infrared spectroscopy. New bands appeared at 1661 and 916 cm^?1 in the spectra of amidoximated bagasse and its pulps ion exchangers due to the formation of C?N and N? OH groups. The thermal properties of these ion exchangers is also studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 303–311, 2006     

Grafting acrylonitrile and acrylic acid monomers on cellulosic materials

Graft copolymers of acrylonitrile and of acrylic acid monomers on cellulosic materials were obtained by use of ceric ion initiator in aqueous medium at a 50% (w/w) cellulose-monomer ratio. The variations of poly(acrylonitrile) grafts and of the efficiency of grafting with ceric ion concentration, and of poly(acrylic acid) grafts with temperature are examined. The dependence of water retention capacity of the grafted fibers with the graft level is reported.     

Isolation and identification of residual chromophores in cellulosic materials

A general procedure was developed for the isolation of residual chromophores in or on cellulosic material, which were hitherto inaccessible to structure elucidation due to their extremely low content in the ppb concentration scale. It is applicable to cellulosic pulp, cellulosic fibers (viscose, Lyocell) and cellulose derivatives (acetate, carbonyl-labeled cellulose) as well. The chromophore identification comprises treatment of the cellulosic material with boron trifluoride-acetic acid complex (BF₃·2HOAc) containing sulfite, chromatographic separation of the resulting chromophore-containing mixture, and structure determination of the main constituents by NMR/MS and comparison to authentic samples. Both adsorbed and covalently bound aromatic and quinoid compounds are selectively released by the treatment. Covalent ester, ether and secondary alkyl links between chromophore and cellulose are broken.Four cellulosic example substrates have been analyzed for their chromophore content: Lyocell fibers, cellulose triacetate, pulp after thermal treatment in N,N-dimethylacetamide, and pulp containing carbonyl-selective labels, and up to 11 chromophores per sample have been identified.     

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     

Effect of ionizing radiation on the properties of cellulosic materials

Conclusions -- It has been shown by x-ray diffraction and sorption methods that the radiolysis of cellulose does not cause changes in its ordered regions.-- The change in viscosity mean degree of polymerization of celluloses under the action of -quanta does not depend on the degree of crystallinity of the starting celluloses.-- Intensity of change in DP under the action of -radiation depends on the DP of the starting unirradiated cellulose; the higher the DP of the unirradiated cellulose, the more intensive is the degradation at the same absorbed dose.Translated from Khimicheskie Volokna, No. 1, pp. 54–55, January–February, 1991.     

Atmospheric pressure plasma enhanced synthesis of flame retardant cellulosic materials

Flame retardant cellulosic materials have been produced using a silicon dioxide (SiO₂) network coating. SiO₂ network armor was prepared through hydrolysis and condensation of the precursor tetraethyl orthosilicate (TEOS), prior coating the substrates, and was cross linked on the surface of the substrates using atmospheric pressure plasma (APP) technique. Because of protection effects of the SiO₂ network armor, the cellulosic based fibers exhibit enhanced thermal properties (characterized by TGA and DSC) and improved flame retardant (proven by ASTM D1230‐99). Furthermore, the surface analysis (XPS and SEM) confirmed the presence of the SiO₂ network attached to the substrates even after intense ultrasound washes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Ability of cellulosic materials to initiate graft copolymerization by photo-irradiation

The ability of various kinds of cellulose samples to initiate graft copolymerization of methyl methacrylate by photo-irradiation was examined. Untreated samples (absorbent cotton, sulfite pulp, dissolving pulp, and semichemical pulp), extracted samples (1% sodium hydroxide, methanol, and ethanol-benzene mixture as extraction solvent), oxidized samples (periodic acid, sodium hypochlorite, hydrogen peroxide, and nitrogen dioxide), a reduced sample, an oximated sample, and a ferric ion-adsorbing sample were used for the experiments. It was found that impurities in the sample as well as the oxidized states affect the initiation reaction remarkably. It was also noted that the contribution of these factors was remarkable in an irradiation system with a light of wavelength longer than 300 nm, although in the systems using sensitizers or irradiation with a light of shorter wavelength, initiation took place almost indifferent to the cellulose characteristics.     

Calorimetric method of determining degree of crystallinity of cellulosic materials

Conclusions A calorimetric method has been proposed for determining the degree of crystallinity of cellulosic materials; it is based on measuring the heat effects from interaction of cellulose with water.The method is more reliable and simpler as compared with the previously used methods.Translated from Khimicheskie Volokna, No. 2, pp. 58–59, March–April, 1989.