Fractionation and Molecular Weight of Rubber and Gutta-Percha

1942 ◽  
Vol 15 (1) ◽  
pp. 1-16
Author(s):  
A. R. Kemp ◽  
H. Peters
Keyword(s):  
Molecular Weight ◽  
Soluble Fraction ◽  
Average Molecular Weight ◽  
Latex Films ◽  
Molecular Weight Range ◽  
X Ray ◽  
Gutta Percha ◽  
Approximate Composition ◽  
Association Effect ◽  
Insoluble Portion

Abstract 1. Evaporated latex films and Bolivian fine para contain a chloroform-soluble fraction of about 62 per cent, whereas the soluble portion of crepe and smoked sheets is about 86 per cent. The average molecular weight of these sols, which contain the low polymers and “resin”, range from about 130,000 to 180,000, the more soluble type having the lower value. 2. Diffusion and precipitation methods were employed to fractionate R. C. M. A. crepe, and the following data indicate the approximate composition and molecular weight range of the soluble hydrocarbon fractions separated: 3. The chloroform-insoluble portion of crepe contains a nonlinear type of hydrocarbon, judged by x-ray and viscosity studies. These methods show that the chloroform-insoluble portion of ammonia-preserved latex films contain extremely high-molecular rubber hydrocarbon which is easily oriented to give the regular x-ray crystalline pattern for rubber. 4. Freshly tapped latex contains a large proportion of petroleum-ether-soluble fraction, which becomes insoluble in this solvent on standing in the presence of ammonia. Ammonia-preserved latex films are soluble in chloroform or in hexane containing alcohol-acetone or acetic acid; this insolubility is thus an association effect, which is overcome by the addition of a polar solvent. 5. Viscosity studies on fractions of balata and gutta-percha show that their hydrocarbons have an average molecular weight of about 42,000 and cover a narrow polymeric range.

High Performance Size Exclusion Chromatograph with Computerized Data Reduction for Analysis of Polyethylene and Oligomers

1981 ◽  
Vol 64 (4) ◽  
pp. 999-1007
Author(s):  
Roger C Snyder ◽  
Charles V Breder
Keyword(s):  
Molecular Weight ◽  
High Performance ◽  
Average Molecular Weight ◽  
Porous Silica ◽  
Size Exclusion ◽  
Dead Volume ◽  
Shape Distortion ◽  
Molecular Weight Range ◽  
Liquid Chromatograph ◽  
Exclusion Chromatography

Abstract A liquid chromatograph is described for the size exclusion chromatography (SEC) of polyethylene and oligomers. The rigid column packing material was 10 µm diameter porous silica. An infrared spectrophotometer was used as the detector. The chromatograph was designed and operated to minimize the degree of chromatographic peak shape distortion resulting from factors such as system dead volume, detector cell design, sample injection volume, and sample concentration. To compensate for peak spreading and skewing, the chromatographic data were analyzed with an IBM 370/168 computer using an APL program. The molecular weight range covered by this SEC system was 100-500 000. Precision and accuracy of Jhe calculated weight average molecular weight (Mw) values for polyethylene standards over this range were ±3 and s±4%, respectively.

Molecular Weights and Intrinsic Viscosities of Polyisobutylenes

1943 ◽  
Vol 16 (3) ◽  
pp. 493-508
Author(s):  
Paul J. Flory
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Average Molecular Weight ◽  
Chain Structure ◽  
Molecular Weight Range ◽  
Molecular Weights ◽  
Satisfactory Precision ◽  
Heterogeneous Polymers ◽  
Definition Of

Abstract Experimental methods for fractionating polyisobutylene and for determining osmotic pressures have been described. The ratio π/c of osmotic pressure to concentration has been found in the case of cyclohexane solutions of polyisobutylene to vary nonlinearly with concentration, contrary to recent theories advanced by Huggins and the writer. The slope of this relationship appears to be independent of molecular weight. Reliable methods for extrapolating π/c to c=0 have been established, enabling the determination of absolute molecular weights with satisfactory precision up to values of about 1,000,000. Molecular weights of polyisobutylenes calculated from Staudinger's equation are too low; the discrepancy is more than ten-fold at high molecular weights. On the basis of data for carefully fractionated samples covering a two-hundred-fold molecular weight range, the intrinsic viscosity is found to be proportional to the 0.64 power of the molecular weight. This decided deviation from Staudinger's “law”cannot in this instance be attributed to nonlinear chain structure, as Staudinger has sought to do in other cases. This dependence of molecular weight on intrinsic viscosity leads to the definition of a “viscosity average”molecular weight which is obtained when the relationship is applied to heterogeneous polymers. The viscosity average is less than the weight average molecular weight, which would be obtained if Staudinger's equation were applicable, and greater than the number average obtained by osmotic or cryoscopic methods.

Isoprene and Rubber. XIX. The Molecular Size of Rubber and Balata

1930 ◽  
Vol 3 (3) ◽  
pp. 519-521 ◽  
Author(s):  
H. Staudinger ◽  
H. F. Bondy
Keyword(s):  
Molecular Weight ◽  
Organic Solvent ◽  
Average Molecular Weight ◽  
Molecular Size ◽  
Dilute Solution ◽  
Decomposition Products ◽  
Viscosity Measurements ◽  
Gutta Percha ◽  
Preceding Work

Abstract It was shown in the preceding work that a very dilute solution of balata in an organic solvent contains macromolecules in solution and not micelles. The same is true of rubber. On the basis of these findings it is possible to calculate the molecular weight of rubber and balata from viscosity measurements by means of the formula developed in a previous work: M=η8p/c. Km. The supposition is made that the molecules of rubber and balata have the form of threads and double threads, respectively. Also it is necessary to determine the constant KKm, and this may be calculated in the case of low molecular products, where the average molecular weight can be determined as well as the viscosity of the solutions. Such semi-colloidal decomposition products were obtained by heating rubber or gutta-percha in either tetralin or xylene. As shown by the following table the four samples thus obtained gave the constant: 0.3×10−3,5

THE RUBBER HYDROCARBON OF ASCLEPIAS SYRIACA L.

1943 ◽  
Vol 21b (10) ◽  
pp. 219-223 ◽  
Author(s):  
E. B. Paul ◽  
A. L. Blakers ◽  
R. W. Watson
Keyword(s):  
Molecular Weight ◽  
Chromic Acid ◽  
Acid Oxidation ◽  
Low Molecular Weight ◽  
X Ray Diffraction ◽  
Asclepias Syriaca ◽  
X Ray ◽  
Chromic Acid Oxidation ◽  
Gutta Percha ◽  
Diffraction Diagram

Milkweed latex collected in mid-July was coagulated in acetone, the coagulum purified, and the rubber examined by chemical and X-ray diffraction methods. Chromic acid oxidation analyses indicate that the monomer is isoprene. The X-ray evidence verifies these results and, further, fixes the polymer as the cis-configuration (rubber) as opposed to the trans-configuration (gutta-percha) of polyisoprene.The solvent-extracted rubber from the leaves appears from the chromic acid oxidation results to be isoprene, but so far no polyisoprene diffraction diagram has been obtained. It is therefore likely that the solvent-extracted leaf rubber is an isoprene polymer of low molecular weight.

scholarly journals Effect of Various Temperatures on Bletillae Rhizoma Polysaccharide Extraction and Physicochemical Properties

2018 ◽  
Vol 9 (1) ◽  
pp. 116 ◽  
Author(s):  
Xiaoyan Long ◽  
Quan Yan ◽  
Linwei Peng ◽  
Xinyue Liu ◽  
Xuegang Luo
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Extraction Temperature ◽  
X Ray Diffraction ◽  
Simple Process ◽  
X Ray ◽  
Gel Permeation ◽  
Scanning Electron

Six fractional polysaccharides were prepared by water extraction and alcohol precipitation under controlled temperature from bletillae rhizoma, a traditional Chinese medicine. Based on this, yields of bletillae rhizome polysaccharides (RBPs) were obtained. The extracting temperature impacted the characteristics of the fractional polysaccharides. The fractional polysaccharides were characterized by glucomannan (GM) content, thermal stability, scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), and x-ray diffraction (XRD). For the analysis, 2.0% w/v dispersions of the six fractional polysaccharides were prepared and their flow behaviors were evaluated using a rotational rheometer. The results showed that increased extraction temperature led to increased GM extraction yields and extraction rate, but GM content was relative stable (over 90%). The average molecular weight (Mw) of fractional polysaccharides obtained at 30, 40, 50, 60, 70, and 80 °C was 3.598 × 104, 4.188 × 104, 8.632 × 104, 8.850 × 104, 2.372 × 105, and 3.081 × 105 g/mol, respectively. SEM revealed that fractional polysaccharides had a porous structure of different sizes and densities. Thermal analysis, FTIR, and XRD results indicated that extraction temperature affects the structure and moisture content of fractional polysaccharides. All results showed that the extraction temperature has an obvious impact on the morphology, molecular weight, and polydispersity of the RBPs. This simple process is a promising method for the preparation of fractional polysaccharides.

scholarly journals ENHANCEMENT OF GAMBE CLAY USING UN-FERMENTABLE POLYMERS FOR DRILLING MUD FORMULATION

2016 ◽  
Vol 36 (1) ◽  
pp. 119-126
Author(s):  
AO Ibrahim ◽  
OR Momoh ◽  
MT Isa
Keyword(s):  
Molecular Weight ◽  
Drilling Fluid ◽  
Average Molecular Weight ◽  
Chemical Properties ◽  
Methyl Cellulose ◽  
Carboxy Methyl Cellulose ◽  
Drilling Mud ◽  
X Ray ◽  
Gas Drilling ◽  
Carboxy Methyl

There is availability and large deposits of bentonite (700 million tons in North Eastern part) in Nigeria but the clays had not been abundantly harnessed and enhanced with polymer for drilling fluid formulation because they are mostly composed of calcium montmorillonite. This work was aimed at enhancing Gambe clay using un-fermentable polymers (three carboxy methyl cellulose (CMC) with different average molecular weight). The clay was obtained from Gambe town in Adamawa State, Nigeria, beneficiated for quartz removal, as well as enhancement with Na2CO3 (6 wt.%). The mineral and oxides composition of the clay was determined using X-ray diffraction and X-ray fluorescence analyses respectively, and finally used to formulate the drilling fluid. The effect of the polymer on the rheological and physico-chemical properties of the formulated drilling fluid was investigated employing FANN 35SA viscometer.  It was found that the carboxy methyl cellulose enhanced the plastic viscosity from 1.5 cP to 34 cP and the apparent viscosity from 2.25 cP to 44 cP. The higher the average molecular weight of the sodium carboxy methyl cellulose the higher the apparent and plastic viscosities of the formulated fluid. Similarly, the resultant viscosities compared well with that of commercial standard of 15 cP and 14 cP of apparent and plastic viscosities respectively. The sets of data generated from this work is going to be very useful for water and oil/gas drilling operations. http://dx.doi.org/10.4314/njt.v36i1.15

scholarly journals Comparative Investigation of Cellular Effects of Polyethylene Glycol (PEG) Derivatives

Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 279
Author(s):  
Ha Pham Le Khanh ◽  
Dániel Nemes ◽  
Ágnes Rusznyák ◽  
Zoltán Ujhelyi ◽  
Pálma Fehér ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Flow Cytometry ◽  
Large Scale ◽  
Biological Effects ◽  
Average Molecular Weight ◽  
Annexin V ◽  
Statistical Correlation ◽  
Molecular Weight Range ◽  
Cellular Effects ◽  
Different Molecular Weight

Nowadays, polyethylene glycols referred to as PEGs are widely used in cosmetics, consumer care products, and the pharmaceutical industry. Their advantageous properties such as chemical stability, low immunogenicity, and high tolerability explain why PEGs are applied in many fields of pharmaceutical formulations including parenteral, topical, ophthalmic, oral, and rectal preparations and also in modern drug delivery systems. Given their extensive use, they are considered a well-known group of chemicals. However, the number of large-scale comparative studies involving multiple PEGs of wide molecular weight range is low, as in most cases biological effects are estimated upon molecular weight. The aim of this publication was to study the action of PEGs on Caco-2 cells and G. mellonella larvae and to calculate the correlation of these effects with molecular weight and osmolality. Eleven PEGs of different molecular weight were used in our experiments: PEG 200, PEG 300, PEG 400, PEG 600, PEG 1000, PEG 1500, PEG 4000, PEG 8000, PEG 10,000, 12,000, and PEG 20,000. The investigated cellular effects included cytotoxicity (MTT and Neutral Red assays, flow cytometry with propidium iodide and annexin V) and autophagy. The osmolality of different molecular weight PEGs with various concentrations was measured by a vapor pressure osmometer OSMOMAT 070 and G. mellonella larvae were injected with the solutions of PEGs. Sorbitol was used as controls of the same osmolality. Statistical correlation was calculated to describe the average molecular weight dependence of the different measured effects. Osmolality, the cytotoxicity assays, flow cytometry data, and larvae mortality had significant correlation with the structure of the PEGs, while autophagosome formation and the proportion of early apoptotic cells showed no statistical correlation. Overall, it must be noted that PEGs must be tested individually for biological effects as not all effects can be estimated by the average molecular weight.

scholarly journals MOLECULAR SIZE AND CONFIGURATION OF CELLULOSE TRINITRATE IN SOLUTION

1958 ◽  
Vol 36 (6) ◽  
pp. 952-969 ◽  
Author(s):  
M. M. Huque ◽  
D. A. I. Goring ◽  
S. G. Mason
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Ethyl Acetate ◽  
Average Molecular Weight ◽  
Molecular Size ◽  
Random Coil ◽  
Radius Of Gyration ◽  
Molecular Weight Range ◽  
Scattering Measurements ◽  
The Relationship

Viscosity and light-scattering measurements were made on several fractions and two unfractionated samples of cellulose trinitrate. The samples were prepared from bleached ramie, unbleached ramie, and cotton linters. The solvents were acetone and ethyl acetate. Viscosity was measured in a multishear viscometer designed for the purpose. Light-scattering measurements were made in a Brice-Phoenix Light-scattering Photometer modified to accommodate a cell which could be ultracentrifuged.The range of molecular weight investigated was from 6.5 × 105 to 25.0 × 105 The relationship between the z-average mean-square radius of gyration, [Formula: see text] and the z-average molecular weight was approximately linear in both solvents. The ratio of [Formula: see text] (where [Formula: see text] is the value of [Formula: see text] in the unperturbed state) was found constant in acetone but to increase with [Formula: see text] in ethyl acetate. This indicated that, whereas in acetone random coil configuration was attained, a configurational transition occurred in ethyl acetate in the molecular weight range investigated.The value of the exponent a in the relationship between intrinsic viscosity and molecular weight was found to be lower than unity but approximately equal in both solvents.The significance of the experimental data is discussed.

A tetranuclear Sn(IV) 4-thiazolecarboxylate complex: synthesis, structure and catalytic behavior in the bulk ring-opening polymerization of glycolide

2016 ◽  
Vol 71 (8) ◽  
pp. 843-848 ◽  
Author(s):  
Jian Gao ◽  
Yu Yuan ◽  
Ai-Jun Cui ◽  
Feng Tian ◽  
Ming-Yang He ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Single Crystal ◽  
Ring Opening ◽  
Glycolic Acid ◽  
Average Molecular Weight ◽  
Ring Opening Polymerization ◽  
Number Average Molecular Weight ◽  
X Ray Diffraction ◽  
Catalytic Behavior ◽  
X Ray

AbstractThe reaction of 4-thiazolecarboxylic acid (Htzc) and dimethyltin(IV) dichloride with NaOH in mixed MeOH-H2O solvent led to the formation of a new Sn(IV) complex (Me2Sn)4(μ3-O)2(tzc)4 (1). Its structure has been characterized by elemental analysis, IR spectroscopy and single crystal and powder X-ray diffraction. Single-crystal X-ray diffraction revealed that complex 1 crystallizes in the monoclinic P21/c space group with Z = 2 and has a tetranuclear structure with crystallographically imposed centrosymmetry. The as-synthesized complex 1 was found to be active toward the bulk solvent-free polymerization of glycolide, producing poly(glycolic acid) with a number-average molecular weight up to 55.5 kDa.

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