摘要:

The equilibria of mildly saponified W. hemlock wood meal with aqueous sodium hydroxide were studied in the concentration range 0.5 to 5.0 N, using added sodium chloride to characterize the Donnan effects involved in the equilibria. With increasing alkali concentration, the alkali reversibly consumed by the wood meal increases, reaching the value of 1.7 eq/kg dry wood. Quantitative determinations of the accompanying increase in anionic groups associated with the wood matrix suggest that these groups are formed predominantly through the ionization of monomeric units in polysaccharides, behaving as very weak monobasic acids. Comparison of results obtained for mercerized and unmercerized wood indicate that 63 % of the polysaccharides in the latter case are accessible to equilibration at alkali concentrations of 2 N and below. Elimination of Donnan effects by sufficiently high added sodium salt concentrations can be used to determine the average acidic dissociation constant of polysaccharides in mercerized wood. The value found for ambient temperature, 0.93 · 10−14, declines slowly with increasing temperature. Water associated with the inner solution was found to increase from 0.6 to 1.3 g/g wood with increasing hydroxyl ion concentration from 0.5 to 2.0 N. In the same alkalinity range, the ratio of inner to outer hydroxyl ion concentration was shown to increase from 0.55 to 0.70 when the measurements were carried out in the presence of 0.5 M NaCl. The importance of polysaccharide ionization and accompanying Donnan effects in the interpretation of kinetic kraft pulping studies is demonstrated.

ISSN:0277-3813    

DOI:10.1080/02773819108050258

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The molecular weight distributions (MWD) of unbleached kraft pulps ofPinus radiataandPopulus tremuloideswere determined by size exclusion chromatography (SEC) of the carbanilated derivatives. The applicability of this method for the study of the effects of xylanase treatments on these substrates is discussed.

ISSN:0277-3813    

DOI:10.1080/02773819108050259

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

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−1when 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.

ISSN:0277-3813    

DOI:10.1080/02773819108050260

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

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−1region due to formation of carbonyl groups.

ISSN:0277-3813    

DOI:10.1080/02773819108050261

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Inverse Gas Chromatography (IGC) was used to characterize chemithermomechanical pulp (CTMP) wood fiber surfaces modified by polymer grafting. From the retention times at infinite dilution over a range of temperatures, the differential heat of adsorption, ΔHoA, the standard free energy, ΔGoA, and the standard entropy of adsorption, ΔSoA, have been determined for the n-alkanes vapors C8-C11on CTMP wood fibers grafted with poly(methylmethacrylate) (PMMA) at various polymer loadings (PL). The dispersive component of the surface free energy γLS (London) has also been calculated by using a method based on the increment of ΔGoA per CH2group. Comparison of results for the original material, CTMP and PMMA, with those of the grafted fibers has allowed the evaluation of surface modification. Grafted samples at high PL show values of ΔHoA, ΔGoA, and γLS approaching those of the pure PMMA indicating a high density of polymer chains grafts on the CTMP wood fiber.

ISSN:0277-3813    

DOI:10.1080/02773819108050262

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Cross polarization, magic-angle spinning, interrupted decoupling and paramagnetic doping techniques have been combined to provide the sensitivity needed for detection of chemical functional groups involved in pulp bleaching reactions. Cold soda pulp and stone groundwood pulp were bleached by calcium hypochlorite and hydrogen peroxide respectively. These treatments had little effect on ketonic structures and no effect on etherified aryl units, but hypochlorite degraded most lignin units not linked in beta-0–4 ethers. This work provides direct confirmation of published predictions based on bleaching of model compounds in solution.

ISSN:0277-3813    

DOI:10.1080/02773819108050263

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Laser-induced fluorescence has been used to examine changes in lignin and black liquor during the course of kraft pulping. When excited with a laser at 457 and 488 nm, lignin samples isolated during the course of pulping, purified, and redissolved in alkali exhibited increasing fluorescent emission intensity. This may be explained by changes in lignin structure during pulping. At higher excitation wavelengths, differences between samples diminished. Black liquors showed decreasing fluorescent intensity with increasing pulping. We attribute this behavior to the increase in optical density of the liquors as cooking time proceeds. The optical density increases with cooking time proceeds. The optical density increases with cooking time because greater amounts of lignin and other materials dissolve from the wood and enter the black liquor.

ISSN:0277-3813    

DOI:10.1080/02773819108050264

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The aim of this project was to investigate possible methods for the concentration of acid hydrolyzate obtained from hydrolyzing wood. A detailed study of concentration of sugar solution by reverse osmosis, RO, has been performed as well as a comparison with mechanical vapor recompression evaporation. The comparison has, in this specific case, shown that RO is currently more expensive. The result is, however, highly dependent on investment costs, and future expansion of membrane technology could mean lower area costs which would favor the technology.

ISSN:0277-3813    

DOI:10.1080/02773819108050265

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0277-3813    

DOI:10.1080/02773819108050257

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor