The composition and digestibility of corn stover leaves and stems after prolonged NH3 treatment was compared with that after isonitrogenous NH3 addition (NH3 control), represented by samples ...immediately frozen after initial NH3 application. Ammonia treatment decreased concentration of hemicellulose in leaves, particularly arabinose residues. Concentration of saponifiable hydroxycinnamic acids was reduced by NH3 treatment in upper stems only. Ammonia addition, compared to a H2O control, increased the extent of in vitro fiber degradation of all plant fractions but the rate of fiber degradation for leaves only. Ammonia treatment increased the extent of fiber degradation over NH3 addition in leaves but not in stems. The variable response to NH3 treatment among stover fractions of drought-stressed corn may be related to the high concentration of water-soluble carbohydrates in the stalks and immobilization of NH3-N with lignin. Keywords: Ammoniation; Zea mays; lignin; hemicellulose; hydroxycinnamic acids; NPN immobilization; digestibility
Compostable films for such uses as packaging and agricultural soil covering materials were first produced on commercial scale from blends of biodegradable polyesters and a modified kraft lignin. The ...lignin consisted of an industrial product isolated according to the LignoBoost process. The lignin modification involved homogeneous phase reaction with propylene oxide, and the films were melt-blown from a pelletized compound consisting of up to a 30% blend of lignin derivative with commercial biodegradable polyester. The 12–93 μm thick films combined the characteristics of lignin as modulus-building and environmentally degradable polymer with those of the strength-building thermoplastic polyester. Although the modified lignin paralleled the behavior of native lignin in wood by resisting rapid and full conversion to carbon dioxide in a simulated composting environment, two thirds of the film mass biodegraded within 12 weeks of composting, with the remainder turning into (humus-like) water-soluble solids and particles <2 mm in size. The lignin derivatives suffered from the release of trace amounts of malodorous volatiles containing reduced sulfur when subjected to melt-blowing. The objectionable odor was virtually unnoticeable in injection-molded solid parts.
We prepared thermoplastic composite panels using solution impregnation of continuous lyocell (regenerated cellulose) fibers with a cellulose mixed-ester (cellulose acetate butyrate) matrix. We ...examined both fiber-matrix adhesion and melt consolidation in an effort to produce uniform panels having low void content and high mechanical strength. We characterized the effect of surface modification by acetylation on interfacial adhesion between the cellulose fiber and cellulose ester. Whereas wood fiber acetylation had previously been observed to result in significant strength gains in (discontinuous) wood fiber- reinforced composites (with the same matrix material), we did not observe a similar increase in strength in the continuous lyocell cellulose fiber system. This suggests that interfacial stress transfer is not a limitation in this system. This was confirmed by microscopic examination of the fracture surfaces, which indicated that fiber-matrix adhesion was considerable in the absence of fiber surface modification. We then systematically varied melt consolidation conditions (temperature, pressure and time) in an attempt to define optimum consolidation parameters by using design of experiments (DOE) methodology. We measured both interlaminar shear strength (ILSS) and composite void volume. We found that a minimal void content (ca. 2.83 vol. %) occurred at moderate temperatures (200°C), low consolidation pressures (81.4kPa) and long press times (13min). This was also where we maximized the interlaminar shear strength (ILSS) at a value of 16.3MPa. This agrees with the regression model predictions. We observed the highest tensile properties at the ILSS and void-volume optimal-consolidation condition: a tensile modulus of 22GPa and tensile strength of 246MPa were obtained.
The kinetics of the formation of amidized homologs of chitosan from the ionic complexes of chitosan with four alkanoic acids, formic, acetic, propionic and butyric acid, have been studied. Their ...degrees of substitution (DS) and their thermal transitions have been investigated. The results suggest that heating of N-acylates of chitosan produces amidized chitosan homologs with DS ranging between 0.1 and 0.6 as determined by solid state NMR. Thermal analysis by DMTA revealed that the ionic complexes of chitosan with formic, acetic, propionic, and butyric acids, as well as the respective amidized chitosan homologs, display two transitions designated as α- and β-relaxation. There was no indication of melting. The β-relaxations of the ionic complexes were more pronounced than those of their respective amidized chitosan derivatives. The ultimate Tg of the amidized chitosan homologs declined stepwise with acyl substituent size. The Tg-behavior was attributed to both substituent size and DS. Kinetic analysis using Tg-changes with heating time can be used to describe the kinetics of amidization. The formation of amidized chitosan homologs followed first order rate kinetics in a two-stage process, as was reported previously. The activation energy for amidization was constant irrespective of the acid used in the chitosan complex as well as the DS at ultimate Tg. It was 14±1kcal/mol initially and 21±2kcal/mol in the second stage. Since the transition from first to second stage occurs after the change from rubbery to glassy state (vitrification), vitrification is suspected to be responsible for the two-stage kinetics.
The chemistry of several novel bioconversion lignins Glasser, Wolfgang G; Barnett, Charlotte A; Muller, Peter C ...
Journal of agricultural and food chemistry,
09/1983, Letnik:
31, Številka:
5
Journal Article
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