Long Chain Branching in Natural Hevea Rubber-Determination by Gel Permeation Chromatography

1981 ◽  
Vol 54 (1) ◽  
pp. 34-41 ◽  
Author(s):  
J. L. Angulo-Sanchez ◽  
P. Cabaulero-Mata
Keyword(s):  
Molecular Weight ◽  
Soluble Fraction ◽  
Hydroxylamine Hydrochloride ◽  
Gel Permeation Chromatography ◽  
Branch Points ◽  
Long Chain Branching ◽  
Molecular Weights ◽  
Gel Permeation ◽  
The Relationship ◽  
Long Chain

Abstract The hevea brasiltensis rubber contains, besides the insoluble branched entities, linear and branched molecules in the soluble fraction. The branching characteristics found by analyzing fractions of different molecular weight of rubber coagulated from freshly tapped latex, stabilized with hydroxylamine hydrochloride are: (a) molecules with molecular weights above 6.5×104−1.0×105g/mol (depending on the branch points functionality) are branched and molecules below these limits are linear. (b) The relationship between number of branch points and the logarithm of molecular weight is linear. (c) The branching density is not independent of molecular weight, as has been assumed for several polymers, but it has a maximum. The maximum branching density found in the soluble fraction is between 10.2×10−6 and 31.6×10−6mol/g, which varies little with the molecular weight; it is possible that molecular species with higher values become insoluble. (d) Branching results ˜λ and gel content (36%) of the whole rubber gave a total of 93–98% of branched entities (sol and gel) and 2–7% of linear species.

Long-Chain Branching and Mechanism Controlling Molecular Weight in Hevea Rubber

1999 ◽  
Vol 72 (4) ◽  
pp. 712-720 ◽  
Author(s):  
Jitladda Tangpakdee Sakdapipanich ◽  
Tippawan Kowitteerawut ◽  
Krisda Suchiva ◽  
Yasuyuki Tanaka
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Branch Points ◽  
Long Chain Branching ◽  
Linear Character ◽  
Close Relationship ◽  
Deproteinized Natural Rubber ◽  
Long Chain

Abstract The linear character of transesterified deproteinized natural rubber (DPNR-TE) was confirmed by the analysis of terminal groups with NMR and viscometric analyses. The branch content of DPNR rubber from fresh latex was found to range from 0.3 to 1.3 and 0.7 to 3.2, based on tri- and tetra-functionalities, respectively. The plot between the number of branch-points and molecular weight (MW) can be divided into three fractions: (A) the rubber fractions in MW ranging from 2.4×105 to 1.9×106; (B) between 1.9×105 and 2.4×105; and (C) those of MW less than 1.9×105. The fraction (A) showed the number of branch-points per a branched molecule (m) higher than that of fractions (B) and (C). This plot is superimposable with the bimodal molecular-weight distribution (MWD) of Hevea rubber, showing a good coinciding of peak-tops at the high and low MW fractions. It seems likely that there is a close relationship between the number of branch-point and bimodal MWD of natural rubber.

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%.

Structural studies of oligosilanes produced by catalytic dehydrogenative coupling of primary organosilanes

1987 ◽  
Vol 65 (8) ◽  
pp. 1804-1809 ◽  
Author(s):  
C. Aitken ◽  
J. F. Harrod ◽  
U. S. Gill
Keyword(s):  
Molecular Weight ◽  
Nuclear Magnetic Resonance ◽  
Gel Permeation Chromatography ◽  
Structural Studies ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Dehydrogenative Coupling ◽  
Weight Distributions ◽  
Gel Permeation ◽  
End Groups

The structures of some poly(organosilylenes), [Formula: see text] (R = Ph, p-tolyl, n-hexyl, and benzyl), produced by catalytic dehydrogenative coupling of primary silanes have been studied by infrared, nuclear magnetic resonance, and mass spectroscopies. These results, combined with data on molecular weights and molecular weight distributions from vapour pressure osmometry and gel permeation chromatography, lead to the conclusion that the polymers are linear and have SiH2R end groups. The polymers all have degrees of polymerization of ca. 10 and very narrow molecular weight dipersions. Some possible features of the mechanism that gives rise to this behaviour are discussed.

scholarly journals Molecular Simulation of Hyperbranched Polyester

2009 ◽  
Vol 5 (1) ◽  
pp. 563-569
Author(s):  
Liu Yanmei ◽  
Li Haihua ◽  
Tai Yulei ◽  
Chao Guoku ◽  
Zhao Yajuan
Keyword(s):  
Molecular Weight ◽  
Simulation Model ◽  
Empirical Equation ◽  
Gel Permeation Chromatography ◽  
Acid Value ◽  
Hyperbranched Polyester ◽  
Molecular Weights ◽  
The Core ◽  
Relationship Of ◽  
The Relationship

A new types of hyperbranched polyester was synthesized by the 2,2-bis(hydroxymethyl) propionic acid as an AB2-type monomer and glycerol as the core moiety. Molecular weights were confirmed by Gel Permeation Chromatography. Acid values were titrated by KOH. The hydroxy value was obtained by titration. Furthermore, we calculate logarithmic value of acid value, hydroxy value, and molecular weight, respectively, and the simulation model curves were obtained. Based on the simulation model curves, we establish the empirical equation of the relationship of molecular weight, acid value and hydroxy value.

Methods of long chain branching detection in PE by triple-detector gel permeation chromatography

2015 ◽  
Vol 132 (28) ◽  
pp. n/a-n/a ◽  
Author(s):  
Thipphaya Pathaweeisariyakul ◽  
Kanyanut Narkchamnan ◽  
Boonyakeat Thitisuk ◽  
Wallace Yau
Keyword(s):  
Gel Permeation Chromatography ◽  
Chain Branching ◽  
Long Chain Branching ◽  
Gel Permeation ◽  
Long Chain

Comparison of Number—Average Molecular Weights Calculated by GPC and Membrane Osmometry

1973 ◽  
Vol 46 (1) ◽  
pp. 115-126
Author(s):  
M. R. Ambler ◽  
R. D. Mate
Keyword(s):  
Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Appreciable Amount ◽  
Diffusion Limit ◽  
Low Molecular Weight ◽  
Molecular Weights ◽  
True Value ◽  
Usual Manner ◽  
Gel Permeation ◽  
Polymer Species

Abstract Data are presented which show that when a polymer contains an appreciable amount of low molecular weight species below the diffusion limit of the osmometer membrane, the osmotic molecular weight, Mn, is generally higher than the Mn calculated from gel-permeation chromatography (GPC). Experiments were performed on samples of poly(vinylchloride) (PVC) and high-cis poly (butadiene) polymers. Osmotic data were obtained in the usual manner, while GPC data were obtained using the universal calibration approach. It was found that when all polymer species below approximately 10,000 molecular weight were excluded from the calculation of Mn by GPC, agreement in Mn was obtained between membrane osmometry and GPC. The data obtained suggest that the choice of Mn as measured by membrane osmometry in the calibration of the GPC should not be done casually, as the measured Mn may not reflect the “true” value of that sample, especially when the polymer sample contains an appreciable amount of low molecular weight material.

Characterization the Relationship between Rheology Behavior and Moleculer Weight of Natural Rubber with Different Protein Content

2011 ◽  
Vol 337 ◽  
pp. 285-288
Author(s):  
Tian Ming Gao ◽  
Rui Hong Xie ◽  
Pu Wang Li ◽  
Mao Fang Huang
Keyword(s):  
Molecular Weight ◽  
Stress Relaxation ◽  
Natural Rubber ◽  
Gel Permeation Chromatography ◽  
Complex Viscosity ◽  
Low Protein ◽  
Nonlinear Viscoelastic ◽  
Gel Permeation ◽  
Linear Viscoelastic ◽  
The Relationship

Test of the rheology behavior for low protein natural rubber(LPNR) were carried out with rubber processing analyzer(RPA), and molecular weight were carried out with gel permeation chromatography(GPC). The results showed that molecular of LPNR is lower than natural rubber(NR), The complex viscosity(n*) of NR is higher than LPNR. The stress relaxation indicate that time of LPNR is faster than NR, it illuminate that LPNR has lower molecular weight than NR, and processing performance have distinct discrepancy between NR and LPNR. The torque(S’) with strain rising indicated that one linear viscoelastic region and one nonlinear viscoelastic region in whole range, and LPNR has lower S’ than NR.

Sign in / Sign up

Export Citation Format

Share Document