scholarly journals Use of Rubber Process Analyzer for Characterizing the Molecular Weight Parameters of Natural Rubber

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Tianming Gao ◽  
Ruihong Xie ◽  
Linghong Zhang ◽  
Hongxing Gui ◽  
Maofang Huang
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Milling Time ◽  
Laser Light ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Sweep Frequency ◽  
Weight Average Molecular Weight ◽  
Molecular Weights ◽  
Strain Sweep

The aim of this work is to introduce a simple and rapid method for characterizing the molecular weight parameters and other molecular structure parameters of natural rubber (NR) using a rubber process analyzer (RPA). In this work, NR of different molecular weights was prepared by milling. Molecular weight parameters were measured by gel permeation chromatography coupled with laser light scattering (GPC-LLS) for comparison with RPA results. It was verified that increasing of milling time leads to a decrease of the number-average molecular weight (M-n), weight-average molecular weight (M-w), and molecular weight distribution (MWD). The dynamic and rheological properties were evaluated on RPA by tests of strain sweep, frequency sweep, and stress relaxation. These results were used to characterize the average molecular weight, MWD, and viscosity of NR and were found to agree with those from GPC-LLS. This convenient and rapid technology for characterizing NR molecular weight parameters would be especially useful in the elastomer industry.

Probing the molecular weights of sweetgum and pine kraft lignin fractions

TAPPI Journal ◽  
2021 ◽  
Vol 20 (6) ◽  
pp. 381-391
Author(s):  
JULIANA M. JARDIM ◽  
PETER W. HART ◽  
LUCIAN LUCIA ◽  
HASAN JAMEEL
Keyword(s):  
Molecular Weight ◽  
Black Liquor ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Systematic Investigation ◽  
Kraft Pulping ◽  
Molecular Weights ◽  
Lignin Recovery ◽  
Lignin Reactivity ◽  
Kinetics Of

The present investigation undertook a systematic investigation of the molecular weight (MW) of kraft lignins throughout the pulping process to establish a correlation between MW and lignin recovery at different extents of the kraft pulping process. The evaluation of MW is crucial for lignin characterization and utilization, since it is known to influence the kinetics of lignin reactivity and its resultant physicochemical properties. Sweetgum and pine lignins precipitated from black liquor at different pHs (9.5 and 2.5) and different extents of kraft pulping (30–150 min) were the subject of this effort. Gel permeation chromatography (GPC) was used to deter- mine the number average molecular weight (Mn), mass average molecular weight (Mw), and polydispersity of the lignin samples. It was shown that the MW of lignins from both feedstocks follow gel degradation theory; that is, at the onset of the kraft pulping process low molecular weightlignins were obtained, and as pulping progressed, the molecular weight peaked and subsequently decreased. An important finding was that acetobromination was shown to be a more effective derivatization technique for carbohydrates containing lignins than acetylation, the technique typically used for derivatization of lignin.

scholarly journals Characterisation of Sequential Solvent Fractionation and Base-catalysed Depolymerisation of Treated Alkali Lignin

BioResources ◽  
2015 ◽  
Vol 10 (3) ◽  
pp. 4137-4151 ◽  
Author(s):  
Aikfei Ang ◽  
Zaidon Ashaari ◽  
Edi Suhaimi Bakar ◽  
Nor Azowa Ibrahim
Keyword(s):  
Molecular Weight ◽  
Chemical Structure ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Solubility Parameters ◽  
Low Molecular Weight ◽  
Sequential Fractionation ◽  
Weight Average Molecular Weight ◽  
Solvent Fractionation ◽  
Alkali Lignin

An alkali lignin (OL) with a weight-average molecular weight (Mw) of 11646 g/mol was used to prepare low-molecular weight lignin for resin synthesis. The low-molecular weight lignin feedstock was obtained via base-catalysed depolymerisation (BCD) treatments at different combined severity factors. Sequential fractionation of the OL and BCD-treated lignins using organic solvents with different Hildebrand solubility parameters were used to alter the homogeneity of the OL. The yield and properties of OL itself and OL and BCD-treated OL dissolved in propan-1-ol (F1), ethanol (F2), and methanol (F3) were determined. Regardless of the treatment applied, a small amount of OL was dissolved in F1 and F2. The BCD treatment did not increase the yield of F1 but did increase the yields of F2 and F3. Gel permeation chromatography (GPC) showed that the repolymerization reaction occurred in F3 for all BCD-treated OL, so these lignins were not suitable for use as feedstocks for resin production. The GPC, 13Carbon-nuclear magnetic resonance, and Fourier transform infrared spectroscopy analyses confirmed that the F3 in OL exhibited the optimum yield, molecular weight distribution, and chemical structure suitable for use as feedstocks for resin synthesis.

SIZE, STABILITY, AND HETEROGENEITY OF APURINIC ACID

1956 ◽  
Vol 34 (6) ◽  
pp. 1107-1117 ◽  
Author(s):  
G. C. Wood ◽  
David B. Smith
Keyword(s):  
Molecular Weight ◽  
Nucleic Acid ◽  
Acid Treatment ◽  
Average Molecular Weight ◽  
Weight Average Molecular Weight ◽  
Molecular Weights ◽  
Size Stability ◽  
Mild Acid

Apurinic acid prepared by mild acid treatment of sodium desoxyribonucleate and of fractions of sodium desoxyribonucleate was sufficiently stable to permit estimations of molecular weight and polydispersity. Apurinic acid from unfractionated desoxyribonucleate had a weight-average molecular weight of 25,000 and was very polydisperse. Preparations from fractionated desoxyribonucleate representing about half the original nucleic acid were much less polydisperse and had molecular weights of about 10,000.

Randomly Branched Polymers. II. Computer Analysis of Gel-Permeation Chromatograms

1976 ◽  
Vol 49 (5) ◽  
pp. 1290-1304
Author(s):  
M. Kurata ◽  
H. Okamoto ◽  
M. Iwama ◽  
M. Abe ◽  
T. Homma
Keyword(s):  
Molecular Weight ◽  
Weight Distribution ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Computer Method ◽  
Branched Polymers ◽  
Branch Points ◽  
Weight Average Molecular Weight ◽  
Degree Of Branching ◽  
Gel Permeation

Abstract An iterative computer method was proposed for estimating the degree of branching and molecular weight distribution simultaneously from a pair of measurements on intrinsic viscosity and gel-permeation chromatography. The validity of the method as applied to randomly branched polymers was tested by using both fractionated and unfractionated samples of branched polystyrenes. It was experimentally concluded that the average number of branch points per unit molecular weight, λ, can be determined by this method with an accuracy of about 15%, and the weight-average molecular weight with accuracy of about 10%.

scholarly journals Synthesis of hydroxyl terminated liquid natural rubber by oxidative depolymerization of deproteinized natural rubber

2016 ◽  
Vol 54 (3) ◽  
pp. 340 ◽  
Author(s):  
Le Duc Giang ◽  
Dinh Long Mong Thao ◽  
Hoang Thi Huong ◽  
Le Thi Thu Hiep
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Chemical Structure ◽  
Spectroscopic Analysis ◽  
Average Molecular Weight ◽  
Analytical Data ◽  
Ammonium Persulfate ◽  
Weight Average Molecular Weight ◽  
Liquid Natural Rubber ◽  
Deproteinized Natural Rubber

Hydroxyl terminated liquid natural rubber (HTLNR) was prepared by the depolymerization of deproteinized natural rubber (DPNR) in mixture of toluene and water at 60oC for 24 hours in the presence of ammonium persulfate as an initiator and tetrahydrofuran (THF) as a homogenizing agent. GPC analysis revealed that the number-average molecular weight (Mn) and weight-average molecular weight (Mw) of HTLNR were found to be 4.334×103 g/mol and 11.702×103 g/mol, respectively, with polydispersity index (PDI) of  2.7. The chemical structure of HTLNR was determined by FTIR and 1H-NMR and 13C-NMR spectroscopic analysis. The mechanism of depolymerization and hydroxylation of NR to form HTNR based on the analytical data is also suggested in this study.

SIZE, STABILITY, AND HETEROGENEITY OF APURINIC ACID

1956 ◽  
Vol 34 (1) ◽  
pp. 1107-1117
Author(s):  
G. C. Wood ◽  
David B. Smith
Keyword(s):  
Molecular Weight ◽  
Nucleic Acid ◽  
Acid Treatment ◽  
Average Molecular Weight ◽  
Weight Average Molecular Weight ◽  
Molecular Weights ◽  
Size Stability ◽  
Mild Acid

Apurinic acid prepared by mild acid treatment of sodium desoxyribonucleate and of fractions of sodium desoxyribonucleate was sufficiently stable to permit estimations of molecular weight and polydispersity. Apurinic acid from unfractionated desoxyribonucleate had a weight-average molecular weight of 25,000 and was very polydisperse. Preparations from fractionated desoxyribonucleate representing about half the original nucleic acid were much less polydisperse and had molecular weights of about 10,000.

Gel Permeation Chromatography of Natural Rubber

1972 ◽  
Vol 45 (1) ◽  
pp. 346-358 ◽  
Author(s):  
A. Subramaniam
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Weight Distribution ◽  
Hevea Brasiliensis ◽  
Distribution Curve ◽  
Gel Permeation Chromatography ◽  
Bimodal Distribution ◽  
Fractional Precipitation ◽  
Molecular Weights ◽  
Gel Permeation

Abstract The Waters Model 200 Gel Permeation Chromatograph has been used to study the molecular weight distribution of natural rubber. The cumulative weight distribution curve of synthetic cis-polyisoprene from the GPC method showed fair agreement with the distribution obtained by fractional precipitation. For natural rubber the agreement was not so good. Natural rubber samples from six clones of Hevea Brasiliensis were examined with the GPC. Differences were observed in their distributions. Five clones showed a distinct bimodal distribution. The weight and number average molecular weights from the GPC were found to be too low. Some possible reasons for this have been suggested.

A New Green Process for Synthesising High Quality PLLA Materials

2013 ◽  
Vol 750-752 ◽  
pp. 1377-1380 ◽  
Author(s):  
Hui Li Shao ◽  
Xian Jue Zhou ◽  
Xue Chao Hu
Keyword(s):  
Molecular Weight ◽  
Ring Opening ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Ring Opening Polymerization ◽  
Green Process ◽  
Weight Average Molecular Weight ◽  
H Nmr ◽  
Ft Ir ◽  
C Nmr

Synthesis of Poly(L-lactide) (PLLA) by the ring-opening polymerization (ROP) of L-lactides in supercritical carbon dioxide (SC-CO2) with co-solvent were studied. Effects of kinds of co-solvent on the molecular weight (MW) and the molecular weight distribution (MWD) of the resultant polymers were investigated by the gel permeation chromatography (GPC). The resultant polymers were also characterized with1H NMR,13C NMR and FT-IR. It was found that PLLA with high purity and almost without racemization could be obtained by this technology and the acetone is the best co-solvent for this kind of polymerization. By using stannous octoate as initiator and acetone as co-solvent, PLLA having a weight-average molecular weight (Mw) near to 9×104and polydispersity index (PDI) of 1.7 was successfully synthesized.

Article

1998 ◽  
Vol 76 (11) ◽  
pp. 1699-1706 ◽  
Author(s):  
Jonathan Z Knaul ◽  
Mohammad R Kasaai ◽  
V Tam Bui ◽  
Katherine AM Creber
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Solvent System ◽  
Similar Degree ◽  
Degree Of Deacetylation ◽  
Molecular Weights ◽  
Good Accord ◽  
Gel Permeation ◽  
Weight Analysis

Starting from a chitosan sample with a degree of deacetylation of 71%, three separate sample sets were generated by successive deacetylation and reacetylation processes. The degree of deacetylation of samples was determined by UV spectrometry supported by thermogravimetric analysis. The molecular weight of chitosan samples was determined in a solvent system of 0.25 M CH3COOH/0.25 M CH3COONa, using viscometry and gel permeation chromatography (GPC) with a TSK-gel column. The first set of samples had a similar degree of deacetylation (DDA) but differing molecular weights. The second set of samples had a similar molecular weight but differing degrees of deacetylation. The Mark-Houwink-Sakurada constants used for the determination of viscosity average molecular weight and the universal calibration of the GPC system were K = 1.40 × 10-4 dL/g and a = 0.83. Results showed that molecular weights determined from both techniques are in good accord only at lower degrees of deacetylation. This may be attributed to the fact that the chemical structure of chitosan samples could have been largely altered with increasing or decreasing degree of deacetylation. Nevertheless, the trend with which the molecular weights vary with the deacetylation time is consistent over a limited DDA range. A literature review of molecular weight analysis of chitosan is included.Key words: chitosan, degree of deacetylation, gel permeation chromatography, molecular weight, viscometry.

scholarly journals The Application of Organic Phosphate Nucleating Agents in Polypropylene with Different Molecular Weights

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1543
Author(s):  
Juan Li ◽  
Zhaohua Liang ◽  
Chengtao Gao ◽  
Shanshan Luo ◽  
Shaowen Huang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Nucleating Agent ◽  
Organic Phosphate ◽  
Nucleating Agents ◽  
Tem Analysis ◽  
Molecular Weights ◽  
Dispersed Particles ◽  
Extrusion Method

Two kinds of organic phosphate nucleating agent (NA-11 and NA-21) were used in PP with different molecular weights through the melt extrusion method. The dispersibility of the nucleating agents in PP, and the effect of the nucleating agents on the molecular weight, rheological behavior and crystallization behavior of PP were investigated. SEM and TEM analysis showed that the average radius of the dispersed particles (nucleating agents) was larger in LPP than that in HPP. The good dispersion of NA-21 also created more nucleation embryos for the adsorption of polypropylene molecules than the agglomerated NA-11. The gel permeation chromatography (GPC) analysis showed that the average molecular weight of HPP and LPP both decreased with the addition of a nucleating agent. The rotational rheometer and capillary rheometer analysis showed that the effect of NA-21 on reducing intermolecular entanglement was more significant, whether in HPP or LPP. The addition of NA-21 had less elastic energy storage and better flow stability, and could be processed at a higher speed. Simultaneously, the relaxation time in the blends with LPP was shorter than that with HPP. It was found that the crystallinity and nucleation efficiency of HPP/nucleating agent blends increased remarkably, while there was a barely perceptible increase in LPP/nucleating agent blends.

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