Mastication. V. Separation and Structural Investigation of Natural Rubber-Polymethyl Methacrylate Interpolymers Formed by Mastication

1958 ◽  
Vol 31 (1) ◽  
pp. 58-72
Author(s):  
D. J. Angier ◽  
W. F. Watson
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Polymethyl Methacrylate ◽  
Structural Investigation ◽  
Extraction Methods ◽  
Fractional Precipitation ◽  
Block Polymer ◽  
Gel Effect ◽  
Profound Influence ◽  
Composition And Structure

Abstract Polymerization of methyl methacrylate admixed with natural rubber occurs on rupture of rubber molecules to free radicals by applied shearing forces. The polymeric products after different conditions and extents of reaction have been separated into uncombincd rubber, two interpolymer fractions, and uncombined polymethyl methacrylate by fractional precipitation and extraction methods. The structure of the interpolymers has been investigated by measurement of composition and osmotic molecular weight, ozonolysis to degrade the rubber segments and isolation of the polymethyl methacrylate fragments, autoxidation of the rubber segments, and viscosity measurements on the uncombined rubber. The interpolymer is a linear block polymer containing one polymethyl methacrylate segment and of the order of one or two rubber segments per molecule. The Trommsdorff gel effect has a profound influence on the rate of formation, composition, and structure of the interpolymer.

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.

Relation between Molecular Weights and Physical Properties of Rubber Fractions

1941 ◽  
Vol 14 (3) ◽  
pp. 580-589 ◽  
Author(s):  
G. Gee ◽  
L. R. G. Treloar
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Physical Properties ◽  
High Molecular Weight ◽  
Elastic Properties ◽  
Elastic Material ◽  
Experimental Results ◽  
Molecular Weights ◽  
High Elasticity ◽  
Latex Rubber

Abstract As high elasticity is a property possessed only by substances of high molecular weight, it is of interest to enquire into the relation between the elastic properties of a highly elastic material such as rubber and its molecular weight. An investigation on these lines has been made possible through the work of Bloomfield and Farmer, who have succeeded in separating natural rubber into fractions having different average molecular weights. The more important physical properties of these fractions have been examined with the object of determining which of the properties are dependent on molecular weight and which are not. Fairly extensive observations were made on the fractions from latex rubber referred to as Nos. 2, 3 and 4 by Bloomfield and Farmer, and some less extensive observations were carried out on the less oxygenated portion of fraction No. 1 obtained from crepe rubber (called hereafter 1b) . Before considering these experimental results, and their relation to the molecular weights of the fractions, it will be necessary to refer briefly to the methods used for the molecular-weight determinations, and to discuss the significance of the figures obtained.

scholarly journals Purification and properties of two extracellular β-lactamases from Bacillus cereus 569/H

1970 ◽  
Vol 118 (3) ◽  
pp. 457-465 ◽  
Author(s):  
S. Kuwabara
Keyword(s):  
Molecular Weight ◽  
Bacillus Cereus ◽  
Zinc Sulphate ◽  
Deae Cellulose ◽  
Casein Hydrolysate ◽  
Crystalline Form ◽  
Casamino Acid ◽  
Fractional Precipitation ◽  
Purification And Properties ◽  
Rapid Production

1. When Bacillus cereus 569/H was grown in a casamino acid (casein-hydrolysate) medium containing zinc sulphate rapid production of extracellular β-lactamase II preceded that of β-lactamase I. 2. β-Lactamase I was separated from β-lactamase II by fractional precipitation with ammonium sulphate. 3. β-Lactamase I was purified by a process involving chromatography on Celite and DEAE-cellulose and β-lactamase II by chromatography on DEAE-cellulose after denaturation of β-lactamase I by heat. Both enzymes were obtained in crystalline form. 4. β-Lactamase II prepared in this way appeared to have a higher molecular weight than β-lactamase I and required Zn2+ as a cofactor for both cephalosporinase and penicillinase activities.

Chemical Depolymerisation of Natural Rubber in Biphasic Medium

2014 ◽  
Vol 1024 ◽  
pp. 193-196
Author(s):  
Ibrahim Suhawati ◽  
Asrul Mustafa
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Chemical Structure ◽  
Inner Core ◽  
Particle Surface ◽  
Natural Rubber Latex ◽  
Carbonyl Groups ◽  
Latex Particles ◽  
Liquid Natural Rubber ◽  
Biphasic Medium

The molecular weight of natural rubber (NR) can be reduced via depolymerization reaction to produce liquid natural rubber (LNR) with a molecular weight less than 50 000 g/mol. In the reaction, hydrogen peroxide and sodium nitrite were added to natural rubber latex to initiate a redox type reaction which then breaks the NR chain. Low permeation of reagents into latex particles allows the degradation to occur greater at the latex particle surface relative to the inner core contributes to high molecular weight distribution (MWD) or polydispersity of the LNR obtained. In this recent works, the reaction was carried out in a biphasic medium consisting of water and toluene phases. Toluene swells latex particles as indicated by the SEM micrographs showing changes in the size of latex particles. This occurrence is suggested to increase the influx of reagents into the latex particles. Consequently, with higher permeation of reagents into the latex particles resulted in the decrease of molecular weight and lower polydispersity of the LNR obtained. Chemical structure analysize showed that the LNRs obtained were attached with hydroxyl and carbonyl groups.

Temperatures of Vitrification and Fluidity of Natural Rubber of Different Molecular Weights

1956 ◽  
Vol 29 (1) ◽  
pp. 95-98
Author(s):  
A. Tager ◽  
M. Iovlova ◽  
T. Kantor ◽  
L. Muzheva
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Vitrification Temperature ◽  
Molecular Weights

Abstract The vitrification temperature of natural rubbers does not change with change of molecular weight, whereas the higher the molecular weight of the rubber, the higher is its fluidity temperature.

The Influence of Molecular Weight on the Orientation and Properties of Polymethyl Methacrylate Sheets

2018 ◽  
Vol 45 (2) ◽  
pp. 47-51
Author(s):  
I.D. Simonov-Emel'yanov ◽  
K.V. Shirshin ◽  
P.V. Motsinov ◽  
S.V. Vlasov
Keyword(s):  
Molecular Weight ◽  
Elastic Modulus ◽  
Polymethyl Methacrylate ◽  
Considerable Increase ◽  
Deformation Characteristics ◽  
Physicomechanical Characteristics

The influence of molecular weight on the process of orientation stretching and the combination of physicomechanical characteristics of specimens of polymethyl methacrylate (PMMA) is examined. Orientation stretching and increase in the molecular weight of PMMA from 0.52 to 4.6 × 106 g/mol lead to a considerable increase in strength and elastic modulus (σt by a factor of 2.6, E by a factor of 2.5). It is established that the deformation characteristics of oriented PMMA specimens increase by a factor of 10 when the molecular weight is increased from 0.52 to 4.6 × 106 g/mol, which opens up new possibilities in the processing of sheets and films of PMMA.

scholarly journals Optimization of high molecular weight DNA extraction methods in shrimp for a long-read sequencing platform

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e10340
Author(s):  
Pacharaporn Angthong ◽  
Tanaporn Uengwetwanit ◽  
Wirulda Pootakham ◽  
Kanchana Sittikankaew ◽  
Chutima Sonthirod ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Genomic Dna ◽  
Extraction Methods ◽  
Marine Organisms ◽  
High Quality ◽  
Sequencing Platform ◽  
Global Food Security ◽  
Long Read ◽  
Ctab Method ◽  
Global Food

Marine organisms are important to global food security as they are the largest source of animal proteins feeding mankind. Genomics-assisted aquaculture can increase yield while preserving the environment to ensure sufficient and sustainable production for global food security. However, only few high-quality genome sequences of marine organisms, especially shellfish, are available to the public partly because of the difficulty in the sequence assembly due to the complex nature of their genomes. A key step for a successful genome sequencing is the preparation of high-quality high molecular weight (HMW) genomic DNA. This study evaluated the effectiveness of five DNA extraction protocols (CTAB, Genomic-tip, Mollusc DNA, TIANamp Marine Animals DNA, and Sbeadex livestock kits) in obtaining shrimp HMW DNA for a long-read sequencing platform. DNA samples were assessed for quality and quantity using a Qubit fluorometer, NanoDrop spectrophotometer and pulsed-field gel electrophoresis. Among the five extraction methods examined without further optimization, the Genomic-tip kit yielded genomic DNA with the highest quality. However, further modifications of these established protocols might yield even better DNA quality and quantity. To further investigate whether the obtained genomic DNA could be used in a long-read sequencing application, DNA samples from the top three extraction methods (CTAB method, Genomic-tip and Mollusc DNA kits) were used for Pacific Biosciences (PacBio) library construction and sequencing. Genomic DNA obtained from Genomic-tip and Mollusc DNA kits allowed successful library construction, while the DNA obtained from the CTAB method did not. Genomic DNA isolated using the Genomic-tip kit yielded a higher number of long reads (N50 of 14.57 Kb) than those obtained from Mollusc DNA kits (N50 of 9.74 Kb). Thus, this study identified an effective extraction method for high-quality HMW genomic DNA of shrimp that can be applied to other marine organisms for a long-read sequencing platform.

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.

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