Destructive Hydrogenation of High-Molecular-Weight Polymers. Isobutene Polymer, Butadiene Polymer, and Natural Rubber

1940 ◽  
Vol 13 (4) ◽  
pp. 849-855
Author(s):  
Vladimir N. Ipatieff ◽  
Raymond E. Schaad
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Nickel Oxide ◽  
The Other ◽  
Large Molecules ◽  
Synthetic Rubber ◽  
Destructive Hydrogenation ◽  
Future Publication ◽  
Proper Interpretation ◽  
Naphthenic Hydrocarbons

Abstract Destructive hydrogenation under pressure in the presence of nickel oxide and molybdenum oxide has been used to show the presence of naphthenic hydrocarbons in high-boiling olefin polymer. It was of interest to apply this tool to other hydrocarbons having large molecules, especially rubber and synthetic rubber like polymers. The destructive hydrogenation of isobutene polymer yielded only paraffinic hydrocarbons, including isobutane in the gases. Butadiene polymer, on the other hand, gave only naphthenic products, chiefly ethylcyclohexane and a dicyclic hydrocarbon. Similarly, natural rubber yielded only naphthenes, with p-methylisopropylcyclohexane as the major component of the lower boiling portion of the product. Isoprene, under the conditions used for the destructive hydrogenation of the rubber, yielded isopentane and an unsaturated naphthene, i. e., a hydropolymer of isoprene, which was converted into p-methylisopropylcyclohexane by further hydrogenation. Discussion of the relation of these results to the structures of the polymeric substances hydrogenated is reserved for a future publication of further work now in progress undertaken to aid in the proper interpretation of the above indicated experiments.

Determination of Peroxides in Synthetic Rubbers

1945 ◽  
Vol 18 (4) ◽  
pp. 874-876
Author(s):  
Richard F. Robey ◽  
Herbert K. Wiese
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Quantitative Determination ◽  
High Molecular Weight ◽  
Active Oxygen ◽  
Lower Molecular Weight ◽  
Synthetic Rubber ◽  
High Molecular Weight Polymers ◽  
Methanol Solutions

Abstract Peroxides are found in synthetic rubbers either as the result of attack by oxygen, usually from the air, or as a residue from polymerization operations employing peroxide catalysts. Because of possible detrimental effects of active oxygen on the properties of the rubber, a method of quantitative determination is needed. The concentration of peroxides in substances of lower molecular weight may be determined with ferrous thiocyanate reagent, either titrimetrically as recommended by Yule and Wilson or colorimetrically as by Young, Vogt, and Nieuwland. Unfortunately, many highly polymeric substances are not soluble in the acetone and methanol solutions employed in these procedures. This is also the case with hydrocarbon monomers, such as butadiene, containing appreciable concentrations of soluble high molecular weight polymers. Bolland, Sundralingam, Sutton and Tristram recommended benzene as a solvent for natural rubber samples and the reagent made up in methanol. However, most synthetic rubbers are not readily soluble even in this combination. The following procedure employs the ferrous thiocyanate reagent in combination with a solvent capable of maintaining considerable concentrations of synthetic rubber in solution. The solvent comprises essentially 20 per cent ethanol in chloroform.

Comparative Study on Effect of Natural and Synthetic Antioxidants on Curing Characteristic and Properties of Different Natural Rubber Origin Compounds

2013 ◽  
Vol 812 ◽  
pp. 93-99
Author(s):  
N.H.H. Shuhaimi ◽  
Nadras Othman ◽  
Hanafi Ismail ◽  
S. Sasidharan
Keyword(s):  
Molecular Weight ◽  
Fatigue Life ◽  
Natural Rubber ◽  
Crosslink Density ◽  
Processing Time ◽  
The Other ◽  
Synthetic Antioxidants ◽  
Compression Set ◽  
Rubber Compounds ◽  
Natural And Synthetic

Effect of natural and synthetic antioxidants on curing characteristic and properties of different natural rubber (NR) origin compounds were performed in this study. The evaluations of natural antioxidant (NA) performance in different NR origins were conducted and the changes in curing characteristic, crosslink density, fatigue life and compression set were recorded. The results indicated that Standard Thailand Rubber (STR) compound has longer processing time in curing characteristic due to a longer chain which is high molecular weight. Because of that, crosslink density, fatigue life cycle (Kc) and compression set (%) of STR compound show better result compared to other origins. On the other hand, NR compounds with NA have show better fatigue and compression set compared with trimethylquinoline (TMQ) especially for STR 5L. Thus, NA can be used as an alternative to the commercial antioxidant in all rubber compounds.

Behavior of Different Fractions of Purified Hevea Rubber during Vulcanization

1949 ◽  
Vol 22 (4) ◽  
pp. 994-999
Author(s):  
G. T. Verghese
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
The Other ◽  
Stress Strain ◽  
Strain Behavior ◽  
Other Hand ◽  
The Difference

Abstract Considerable data on the vulcanization characteristics of molecular fractions of ordinary (unpurified) natural rubber are available. There is, on the other hand, little information of any systematic work on the vulcanization of purified rubber and of its fractions. Pummerer and Pahl vulcanized the sol and gel fractions obtained from purified Hevea rubber, and also the purified whole rubber. But apart from a statement that whole rubber vulcanized much faster than the two fractions obtained from it, no details have been published. Vulcanization of purified whole rubber and of its sol and gel fractions was studied also by Smith and Holt. They concluded that the difference which they observed in the stress-strain behavior of the fractions and whole rubber was due to differences in the rubber which persisted through vulcanization. The present paper deals with a study of the vulcanization characteristics of different fractions of purified rubber prepared by a method described in a previous paper. Also, for comparative purposes a similar study was made of the corresponding fractions of unpurified rubber. As the difference in molecular weight of some of the fractions obtained by the above method was rather small, a grouping of the fractions was made as follows :

Vistanex Polybutene—Rubber Blends

1941 ◽  
Vol 14 (2) ◽  
pp. 386-397 ◽  
Author(s):  
S. Longman
Keyword(s):  
Natural Rubber ◽  
Raw Materials ◽  
Petroleum Products ◽  
The Other ◽  
Partial Substitution ◽  
Manufacturing Equipment ◽  
Rubber Industry ◽  
Rubber Blends ◽  
Synthetic Rubber

Abstract From the foregoing data on blends of Vistanex Polybutene and rubber, it is evident that these two materials complement one another. Each has properties which the other lacks, and blends of the two can be made to emphasize the more desirable properties of either one. Extreme flexibility in compounding these blends is possible, since they are perfectly compatible in milled compounds. Therefore, great latitude is given in compounding of these blends to secure any range or degree of properties possible with either of the components. Vistanex Polybutenes should not be considered as synthetic rubber, because they will not vulcanize, and they lack certain characteristics of vulcanized natural rubber. More properly Vistanex Polybutenes should be considered as modifying agents for partial substitution of natural rubber. In many cases, this substitution of a part of the natural rubber in a compound by Vistanex Polybutene confers definite advantages and improves qualities of such compounds for special uses. Therefore, Polybutenes, even in normal times, have a very definite field of usefulness and, in the event that imports of natural rubber become restricted, the availability of the Vistanex Polybutenes in quantity will be of increasing importance to the rubber industry. Since the raw materials for the manufacture of Vistanex Polybutene are petroleum products, the availability of raw materials is a source of no difficulty in this country. Likewise, the manufacturing equipment is not excessively expensive, and, with expanded production, lowered prices may confidently be expected.

Vulcanization of GR-S by the Peachey Process

1947 ◽  
Vol 20 (1) ◽  
pp. 182-183
Author(s):  
Archibald T. McPherson
Keyword(s):  
Hydrogen Sulfide ◽  
Sulfur Dioxide ◽  
Natural Rubber ◽  
Glass Tube ◽  
The Other ◽  
Curing Process ◽  
Sulfide Sulfur ◽  
Simple Apparatus ◽  
Synthetic Rubber

Abstract It has been found possible to vulcanize GR-S synthetic rubber by subjecting it alternately to hydrogen sulfide and sulfur dioxide gases. This method for curing, known as the Peachey process, was used for natural rubber as long ago as 1921. A simple apparatus was constructed, in which strips of thinly milled rubber were placed on a screen inside a glass tube. One end of this tube was attached to valves connecting it to tanks of hydrogen sulfide, sulfur dioxide, and air, respectively. The other end of the tube led to a series of traps containing solutions which absorbed or destroyed the gases. For each test performed, natural rubber samples were placed inside the tube along with the GR-S samples for comparison. Each strip was weighed before it was inserted in the apparatus. Hydrogen sulfide was first slowly passed over the samples for a period of five minutes. Then air was blown through for a few seconds—just long enough to free the surroundings from the sulfide gas, but not long enough for the gas to be lost from solution in the rubber. Sulfur dioxide gas was next admitted and allowed to pass over the samples for five minutes. A subsequent short sweep of air through the tube completed one cycle of the curing process.

The Elasticity of Rubber-Bitumen Binders for Use in Roads

1964 ◽  
Vol 37 (2) ◽  
pp. 457-476
Author(s):  
Jacqueline de Merlier ◽  
J. Leveque ◽  
J. Curchod
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Elastic Properties ◽  
Elastic Recovery ◽  
Test Methods ◽  
The State ◽  
The Other ◽  
Polymer Analysis ◽  
Rubber Blends ◽  
The One

Abstract The authors have first described test methods used, on the one part, to determine, in a simple way, the elastic recovery of binders after deformation, and on the other, to characterize accurately the state of degradation of the rubber within the bitumen by assessing the molecular weight of the dispersed polymer. Analysis and interpretation of results have stressed: (a) the effect of the molecular weight of crude natural rubber on the elastic recovery of bitumen-rubber blends; (b) the effect of the way in which bitumen-crude natural rubber blends are prepared on their elastic properties and (c) the effect of the nature of synthetic elastomers on the elasticity of bitumen blends.

Density Measurements on Synthetic Rubbers

1943 ◽  
Vol 16 (1) ◽  
pp. 244-248 ◽  
Author(s):  
Lawrence A. Wood ◽  
Norman Bekkedahl ◽  
Frank L. Roth
Keyword(s):  
United States ◽  
Natural Rubber ◽  
The United States ◽  
Subsequent Treatment ◽  
The Other ◽  
Actual Measurement ◽  
Density Measurements ◽  
Commercial Importance ◽  
Synthetic Rubber ◽  
Other Hand

Abstract For many purposes the density of a material need be known with an accuracy of only a few per cent. For many materials the density of one sample may differ from that of another by this amount, and no useful purpose may be served by making more precise measurements on individual samples. In natural rubber, the densities of different samples have been shown, in a compilation of twenty-one values, to lie with two exceptions between 0.905 and 0.919 gram per cc. at 25° C. The variations probably represent real differences in the samples and not accidental errors of observation. Since one can seldom know exactly the origin and subsequent treatment of a sample of natural rubber, there is little value in increasing the precision of measurement. Synthetic rubbers, on the other hand, can be regarded as usually produced under conditions which are much better controlled and known. It is logical, then, to measure the density with greater precision and to hope to be able to ascribe significance to its variations from one sample to another. The present work is concerned with the development of a method for preparing specimens of synthetic rubber in a form suitable for precise measurements of the density, the actual measurement by the method of hydrostatic weighings, and a presentation of the results for most of the varieties of synthetic rubber now of commercial importance in the United States.

HES 200/0.5 Is not HES 200/0.5

1995 ◽  
Vol 74 (06) ◽  
pp. 1452-1456 ◽  
Author(s):  
Johannes Treib ◽  
Anton Haass ◽  
Gerhard Pindur ◽  
Ulrich T Seyfert ◽  
Wolfgang Treib ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Hydroxyethyl Starch ◽  
Clinical Relevance ◽  
Dilution Effect ◽  
Repeated Administration ◽  
Plasma Viscosity ◽  
Degree Of Substitution ◽  
Pronounced Increase ◽  
Large Molecules ◽  
Mean Molecular Weight

SummaryThe plasma clearance of hydroxyethyl starch (HES) depends on the initial molecular weight and the degree of substitution. So far, little attention has been paid to the clinical relevance of the C2/C6 substitution ratio of hydroxyethyl starch.10 patients with cerebrovascular circulatory disturbance received hemodilution therapy for 10 days, consisting of 10% HES 200/0.5 (mean molecular weight 200 kD, degree of substitution 0.5) with a C2/C6 ratio of 13.4. A second group of 10 patients received a starch solution with identical initial molecular weight and degree of substitution but with a C2/C6 ratio of 5.7.After the administration of a single dose, no significant differences between the two groups were observed. After repeated administration, significant differences could be detected in hemorheology, coagulation and elimination (p<0.01). The larger C2/C6 ratio led to a higher intravascular mean molecular weight (95 vs. 84 kD), which in turn led to a higher increase in serum concentration during the therapy (14.7 vs.8.6 mg/ml). Hematocrit was lowered more (-30,5 vs. -23,5%) and plasma viscosity was increased more. There was also a more pronounced increase in partial thromboplastin time (+30% vs. +13%) and a factor of 2 larger decrease of factor VIII/von Willebrand factor-complex (p <0.01), which exceeded the dilution effect.The higher C2/C6 ratio of HES 200/0.5/13.4 slows down enzymatic degradation. After repeated administration of this starch, large molecules accumulate which are inefficiently degraded. The same effect has been observed after therapy with highly-substituted HES. This accumulation of large molecules leads to a beneficial longer lasting volume effect. The disadvantages include an increase in plasma viscosity and coagulation disturbances, which cannot be explained with the respective dilution effect alone. For these reasons, the C2/C6 ratio is of clinical relevance and should be included in the product labeling in the future.

The Kidney and Fibrinolysis

1970 ◽  
Vol 24 (01/02) ◽  
pp. 026-032 ◽  
Author(s):  
N. A Marsh
Keyword(s):  
Molecular Weight ◽  
Plasminogen Activator ◽  
Enzyme System ◽  
Normal Animal ◽  
Fibrinolytic Enzyme ◽  
The Other ◽  
Exclusion Chromatography ◽  
Normal Urine ◽  
Renal Origin ◽  
Molecular Exclusion Chromatography

SummaryMolecular exclusion chromatography was performed on samples of urine from normal and aminonucleoside nephrotic rats. Normal urine contained 2 peaks of urokinase activity, one having a molecular weight of 22,000 and the other around 200,000. Nephrotic urine contained three peaks of activity with MW’s 126,000, 60,000 and 30,000. Plasma activator determined from euglobulin precipitate had a MW. in excess of 200,000. The results indicate that in the normal animal, plasma plasminogen activator does not escape into the urine in substantial quantities but under the conditions of extreme proteinuria there may be some loss through the kidney. The alteration in urokinase output in nephrotic animals indicates a greatly disordered renal fibrinolytic enzyme system.The findings of this study largely support the hypothesis that plasma plasminogen activator of renal origin and urinary plasminogen activator (urokinase) are different molecular species.

Rapid Isolation of High Molecular Weight Urokinase from Native Human Urine

1982 ◽  
Vol 47 (03) ◽  
pp. 197-202 ◽  
Author(s):  
Kurt Huber ◽  
Johannes Kirchheimer ◽  
Bernd R Binder
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Human Urine ◽  
Gel Filtration ◽  
Chain Structure ◽  
The Other ◽  
Single Chain ◽  
Apparent Homogeneity ◽  
Sequential Adsorption

SummaryUrokinase (UK) could be purified to apparent homogeneity starting from crude urine by sequential adsorption and elution of the enzyme to gelatine-Sepharose and agmatine-Sepharose followed by gel filtration on Sephadex G-150. The purified product exhibited characteristics of the high molecular weight urokinase (HMW-UK) but did contain two distinct entities, one of which exhibited a two chain structure as reported for the HMW-UK while the other one exhibited an apparent single chain structure. The purification described is rapid and simple and results in an enzyme with probably no major alterations. Yields are high enough to obtain purified enzymes for characterization of UK from individual donors.

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