scholarly journals Study on the preparation and performance comparison of side-chain hydroxyl-terminated polybutadiene derivatives with narrowly molecular weight distribution used for polyurethane

2021 ◽  
pp. 107389
Author(s):  
Lingxiao Ma ◽  
Xiuzhong Zhu ◽  
Wanbin Zhang ◽  
Haitao Zhang ◽  
Jianyong Wang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Performance Comparison ◽  
Side Chain ◽  
And Performance

Fractionation of woodmeal by prehydrolysis and thermal organosolv. Alkaline depolymerization, chemical functionality, and molecular weight distribution of recovered lignins and their fractions

1993 ◽  
Vol 71 (6) ◽  
pp. 779-789 ◽  
Author(s):  
Ronald W. Thring ◽  
Esteban Chornet ◽  
Ralph P. Overend
Keyword(s):  
Molecular Weight ◽  
Solvent Extraction ◽  
Phenolic Compounds ◽  
Nmr Spectroscopy ◽  
Elemental Composition ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Side Chain ◽  
Molecular Weight Fractions ◽  
C Nmr

Thermal organosolv glycol lignins and their fractions have been characterized by means of elemental composition, molecular weight distribution, and 1H and 13C NMR spectroscopy. Fractionation of each lignin by sequential solvent extraction produced fractions of increasing molecular weight and polydispersity. Structures in the highest molecular weight fractions were found to be linked by a high proportion of β-O-4 type bonds, whilst the lowest molecular weight fractions consisted of a high content of saturated aliphatic side-chain structures. A noticeable difference in the content of carbohydrate contaminants in both starting lignins indicated the formation of relatively stable lignin–carbohydrate complexes, especially in the lignin recovered from pretreated wood. In addition, depolymerization of the lignins and their fractions to monomeric compounds was explored using alkaline hydrolytic and nitrobenzene oxidative routes. The highest molecular weight fractions from each lignin were identified as the best candidates for production of useful monomeric phenolic compounds.

scholarly journals Molecular Weight Distribution and Dissolution Behavior of Lignin in Alkaline Solutions

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4166
Author(s):  
Jie Yang ◽  
Mengya Sun ◽  
Liang Jiao ◽  
Hongqi Dai
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Reaction Temperature ◽  
Weight Distribution ◽  
Hydrothermal System ◽  
Average Molecular Weight ◽  
Holding Time ◽  
Side Chain ◽  
Alkaline Solutions ◽  
Dissolution Behavior

Lignin, as the sole renewable aromatic resource in nature, has great potential for replacing fossil resources. However, the complexity of its structure limits its high value utilization, and the molecular weight distribution and dissolution behavior of lignin in alkaline solutions is still unclear. In this study, a conventional lignin separation during the pulping process in an alkaline hydrothermal system was performed by controlling the amount of NaOH, reaction temperature and holding time. Various analysis methods, including GPC, 2D–HSQC NMR and FTIR were used to study the characteristics of lignin fragments dissolved from wood. We were aiming to understand the rule of lignin dissolution and the recondensation mechanism during the process. The results showed dissolution of lignin due to ether bond fracturing by OH− attacking the Cα or Cβ positions of the side chain with penetration of NaOH, and the lignin fragments in solution recondensed into complex lignin with more stable C–C bonds. The experimental results also prove that the average molecular weight increased from 4337 g/mol to 11,036 g/mol and that holding time from 60 min to 120 min at 150 °C with 14 wt% of NaOH.

Tailoring Polymer Molecular Structure in the EPDM Slurry Process

2003 ◽  
Vol 76 (5) ◽  
pp. 1057-1073 ◽  
Author(s):  
Susmita Bhattacharjee ◽  
Harald Bender ◽  
Dilip Padliya
Keyword(s):  
Molecular Structure ◽  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Wide Spectrum ◽  
Side Reaction ◽  
Performance Characteristics ◽  
Polymer Composition ◽  
Long Chain Branching ◽  
And Performance

Abstract EPDM is produced by different polymerization processes. Therefore, careful engineering of polymer micro- and macro- structures is necessary to achieve desired performance characteristics. This review highlights the process capability of the EPDM slurry technology to tailor and control the molecular structural design. The catalyst and the polymerization technology produce EPDMs with a wide spectrum of chemical composition and Mooney viscosity. The relatively narrow molecular weight distribution of the polymers has been designed to offer the best combination of processing and physical properties. A unique technology for incorporation of long chain branching in the polymer has been developed. This highly selective catalyst technology controls the degree of branching and molecular weight distribution without any side reaction, while offering the flexibility to vary polymer composition and molecular weight. The EPDMs made with the modified molecular structure have a good balance of processing and performance characteristics.

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. 

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