scholarly journals Chemical Composition and Thermal Behavior of Kraft Lignins

Forests ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 483 ◽  
Author(s):  
Aleš Ház ◽  
Michal Jablonský ◽  
Igor Šurina ◽  
František Kačík ◽  
Tatiana Bubeníková ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Cost Effective ◽  
Activation Energies ◽  
Industrial Applications ◽  
Raw Material ◽  
Molecular Weight Determination ◽  
Two Samples ◽  
Process Measurements

Lignin has great potential for utilization as a green raw material or as an additive in various industrial applications, such as energy, valuable chemicals, or cost-effective materials. In this study, we assessed a commercial form of lignin isolated using LignoBoost technology (LB lignin) as well as three other types of lignin (two samples of non-wood lignins and one hardwood kraft lignin) isolated from the waste liquors produced during the pulping process. Measurements were taken for elemental analysis, methoxyl and ash content, higher heating values, thermogravimetric analysis, and molecular weight determination. We found that the elemental composition of the isolated lignins affected their thermal stability, activation energies, and higher heating values. The lignin samples examined showed varying amounts of functional groups, inorganic component compositions, and molecular weight distributions. Mean activation energies ranged from 93 to 281 kJ/mol. Lignins with bimodal molecular weight distribution were thermally decomposed in two stages, whereas the LB lignin showing a unimodal molecular weight distribution was decomposed in a single thermal stage. Based on its thermal properties, the LB lignin may find direct applications in biocomposites where a higher thermal resistance is required.

scholarly journals A new general method for the assessment of the molecular-weight distribution of polydisperse preparations. Its application to an intestinal epithelial glycoprotein and two dextran samples, and comparison with a monodisperse glycoprotein

1973 ◽  
Vol 135 (4) ◽  
pp. 649-653 ◽  
Author(s):  
Richard A. Gibbons ◽  
Stephen N. Dixon ◽  
David H. Pocock
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Continuous Distribution ◽  
Distribution Functions ◽  
Intestinal Epithelial ◽  
Cysticercus Tenuicollis ◽  
Molecular Weights ◽  
Two Samples ◽  
General Method

A specimen of intestinal glycoprotein isolated from the pig and two samples of dextran, all of which are polydisperse (that is, the preparations may be regarded as consisting of a continuous distribution of molecular weights), have been examined in the ultracentrifuge under meniscus-depletion conditions at equilibrium. They are compared with each other and with a glycoprotein from Cysticercus tenuicollis cyst fluid which is almost monodisperse. The quantity c−⅓(c=concentration) is plotted against ξ (the reduced radius); this plot is linear when the molecular-weight distribution approximates to the ‘most probable’, i.e. when Mn:Mw:Mz: M(z+1)....... is as 1:2:3:4: etc. The use of this plot, and related procedures, to evaluate qualitatively and semi-quantitatively molecular-weight distribution functions where they can be realistically approximated to Schulz distributions is discussed. The theoretical basis is given in an Appendix.

Molecular Weight Dependence of Relaxation Spectra of Amorphous Polymers in the Rubbery Region. VII. Comparisons of Experimental Relaxation Spectra with Those Estimated from Molecular Weight Distributions

1967 ◽  
Vol 40 (5) ◽  
pp. 1470-1482 ◽  
Author(s):  
G. Yasuda ◽  
E. Maekawa ◽  
T. Homma ◽  
K. Ninomiya
Keyword(s):  
Experimental Data ◽  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Relaxation Spectrum ◽  
Phenomenological Theory ◽  
Homogeneous Distribution ◽  
Relaxation Spectra ◽  
Molecular Weight Dependence ◽  
Two Samples

Abstract In a previous paper, the relationship between the relaxation spectrum of an amorphous high polymer in the rubbery region and the molecular weight distribution function was studied by the phenomenological theory method. We found a simple, direct proportional relationship between them. The reliability of assumptions and approximations made for the theoretical study can be evaluated by comparison of calculated and experimental data. As reported previously, selection of values for the simplified method was optional in calculating molecular weight dependence of the relaxation spectrum of a sample with a homogeneous distribution. Therefore, the feasibility of selection has to be evaluated by comparison of calculated results with observed data. For the comparison, it is necessary to obtain experimental data for a sample having a homogeneous distribution and compare it with calculated results for the relaxation spectrum and molecular weight distribution of the previous paper. However, these data are scarce in the current literature. From available past literature, we selected polystyrene, poly(vinyl acetate) and polyisobutene as typical samples of amorphous high polymers. In addition, experimental data for two samples of polystyrene were included. Thus, data for a total of five samples were compared with calculated results of the previous paper.

Extraction and Partial Purification of Protease from Bilimbi (Averrhoa bilimbi L.)

2013 ◽  
Vol 10 (2) ◽  
pp. 29
Author(s):  
Normah Ismail ◽  
Nur' Ain Mohamad Kharoe
Keyword(s):  
Molecular Weight ◽  
Protein Content ◽  
Ammonium Sulfate ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Protease Activity ◽  
Protein Concentration ◽  
Temperature Stability ◽  
Partial Purification ◽  
Ammonium Sulfate Precipitation

Unripe and ripe bilimbi (Averrhoa bilimbi L.) were ground and the extracted juices were partially purified by ammonium sulfate precipitation at the concentrations of 40 and 60% (w/v). The collected proteases were analysed for pH, temperature stability, storage stability, molecular weight distribution, protein concentration and protein content. Protein content of bilimbi fruit was 0.89 g. Protease activity of both the unripe and ripe fruit were optimum at pH 4 and 40°C when the juice were purified at 40 and 60% ammonium sulfate precipitation. A decreased in protease activity was observed during the seven days of storage at 4°C. Molecular weight distribution indicated that the proteases protein bands fall between IO to 220 kDa. Protein bands were observed at 25, 50 and 160 kDa in both the unripe and ripe bilimbi proteases purified with 40% ammonium sulfate, however, the bands were more intense in those from unripe bilimbi. No protein bands were seen in proteases purified with 60% ammonium sulfate. Protein concentration was higher for proteases extracted with 40% ammonium sulfate at both ripening stages. Thus, purification using 40% ammonium sulfate precipitation could be a successful method to partially purify proteases from bilimbi especially from the unripe stage. 

Sign in / Sign up

Export Citation Format

Share Document