The Migration of Extender Oil in Natural and Synthetic Rubber. V. Dependence of Diffusion Rates on Oil Concentration and Elastomer Blend Ratios. The Locus of Oil in a Simulated Tire during Service

1971 ◽  
Vol 44 (1) ◽  
pp. 87-105 ◽  
Author(s):  
M. L. Deviney ◽  
L. E. Whittington ◽  
B. G. Corman
Keyword(s):  
Weighted Average ◽  
Fold Increase ◽  
Polymer Composition ◽  
Carbon 14 ◽  
Synthetic Rubber ◽  
Oil Concentration ◽  
Diffusion Rates ◽  
Blend Ratios ◽  
Rubber Product ◽  
Diene Rubber

Abstract Using carbon-14 labelled aromatic extender oil as a penetrant species, diffusion rates were measured in practical elastomeric compounds of high oil concentration, and in elastomer compounds based on blended polymers. These results, combined with earlier data, allow the calculation of the locus of oil during the service life of the rubber product. Increasing the concentration of oil increases the rate of diffusion of oil. Butyl rubber was the most sensitive to this effect, albeit the slowest in rate of migration, with a 2-fold increase in migration rate over the range of oil concentration of 2–27%, followed by polybutadiene, 1.53; natural rubber, 1.27; and ethylene-propylene-diene rubber, 1.26, and SBR, 1.00. Polymer blends display no synergism in their effect on diffusion; the diffusivity of oil in the blends was predicted exactly by the weighted average of polymer composition. Further studies of the effect of dynamic flexing indicated that, at constant temperature, static and dynamic conditions gave equal diffusivities. Calculations were made of the locus of the oil in a simulated tire section at 3000, 6000, 9000, and 24,000 miles. These agree very closely with experi mental results on a vulcanized, aged simulated tire segment.

Migration of Extender Oil in Natural and Synthetic Rubber

1967 ◽  
Vol 40 (5) ◽  
pp. 1570-1584 ◽  
Author(s):  
James E. Lewis ◽  
Marvin L. Deviney
Keyword(s):  
Radioactive Isotopes ◽  
Sufficient Information ◽  
Oil Migration ◽  
Migration Rates ◽  
Carbon 14 ◽  
Modern Computer ◽  
Synthetic Rubber ◽  
Wide Range ◽  
Basic Differential Equation ◽  
Diffusion Rates

Abstract The migration of oil, and in particular, the migration of extender oils in rubber is being studied through the use of radioactive isotopes. Techniques have been developed for uniform carbon-14 labelling of the aromatic-polar fractions of extender oils by Friedel-Crafts reaction and for the uniform labelling of the paraffinic fraction by methylene diradicals generated during photolysis of diazomethane-C14. These techniques formed the basis for a comparative study of the diffusion rates of aromatic and polar, and paraffinic, fractions of a highly aromatic and a paraffinic extender oil in several rubbers which represent a wide range in type of polymeric structure. Faster diffusion rates of both aromatic and polar, and paraffinic fractions, were observed in polybutadiene and natural rubber than in SBR, EPT, and polychloroprene. In most rubbers, paraffinic materials migrated appreciably faster than aromatic and polar fractions. Experiments using Firestone flex blocks indicated that oil migration rates are higher under simulated working conditions than when the sample is subjected to heat treatment alone. Diffusion coefficients for the migrating fractions were calculated from an appropriate solution of the basic differential equation of diffusion using modern computer techniques. The methods which have been developed are suitable for fundamental studies to gain more insight into the mechanisms of diffusion. These experimental methods are also suitable for use in practical studies of oil migration under actual or simulated working and environmental conditions. Ultimately sufficient information should be obtained to permit an accurate prediction of the performance of an extender oil in selected rubbers on the basis of the physical properties of the oil and a quantitative knowledge of the major molecular types present in the oil.

Pyrolysis-GC/MS and TGA as Tools for Characterizing Blends of SBR and NBR

2001 ◽  
Vol 74 (5) ◽  
pp. 803-813 ◽  
Author(s):  
Stephanie R. Shield ◽  
Ghebrehiwet N. Ghebremeskel ◽  
Cebron Hendrix
Keyword(s):  
Degradation Products ◽  
Specific Weight ◽  
Test Methods ◽  
Polymer Composition ◽  
Blend Composition ◽  
Peak Areas ◽  
The Individual ◽  
Blend Ratios ◽  
Analytical Tools ◽  
Technological Interest

Abstract There is increased technological interest to use blends of various dissimilar elastomers in applications for which service, material availability, or cost of a single elastomer do not provide the necessary processing, vulcanizate, or economic properties. Properties of polyblends are sensitive to variations in the amounts of the individual polymers used. Therefore, there is a need for developing a variety of analytical tools that will enable the compounder to monitor the consistency of blend compositions. In this study, the feasibility of using pyrolysis-GC/MS and thermogravimetric analysis (TGA) to estimate the blend composition of SBR/NBR blends was investigated. Pyrolysis-GC/MS degradation products that are characteristic of each polymer were identified. The GC/MS peak areas were used to determine the blend composition. The blend compositions were estimated by TGA from the linear correlation between the polymer composition and the temperature required to pyrolyze a sample to a specific “% weight loss.” The results obtained by pyrolysis-GC/MS and TGA were compared to calculated blend ratios of SBR/NBR in order to estimate the accuracy of the test methods presented in this study.

Migration of Antioxidants and Accelerators in Natural and Synthetic Rubber II. Sulfenamide System Studies and Comparison of Age Resister Migration under Inert and Practical Conditions

1969 ◽  
Vol 42 (3) ◽  
pp. 892-902 ◽  
Author(s):  
James E. Lewis ◽  
Marvin L. Deviney ◽  
Lawrence E. Whittington
Keyword(s):  
Diffusion Coefficient ◽  
Carbon Black ◽  
Natural Rubber ◽  
Count Data ◽  
Diffusion Coefficients ◽  
Oil Migration ◽  
Carbon 14 ◽  
Synthetic Rubber ◽  
End Use ◽  
In Cis

Abstract Radiochemical techniques developed for studying extender oil migration in various elastomers have been adapted for use in investigating the migration of age resisters and curatives. This paper contains basic diffusion coefficient data for nine compounds including both staining and nonstaining antioxidants and members of the sulfenamide, thiazole and thiuram accelerator series. Techniques for synthesizing these age resisters and curatives in the carbon-14 and sulfur-35 labelled form are described. Migration was studied in natural rubber, SBR, cis-polybutadiene and EPT vulcanizates. Computer techniques were used to calculate diffusion coefficients from radiochemical count data. Results from preliminary migration studies under practical curing and end-use conditions are also presented. In the case of phenyl-2-naphthylamine migration in cis-polybutadiene, a pronounced decrease in diffusivity with increasing surface area of the carbon black filler was observed.

Metabolism of Carbon14-Labeled Pyruvate by the Newborn Rat

1955 ◽  
Vol 184 (1) ◽  
pp. 63-68 ◽  
Author(s):  
Ruth Kimmelstiel ◽  
Claude A. Villee
Keyword(s):  
Glycogen Content ◽  
Fold Increase ◽  
Liver Glycogen ◽  
Total Lipids ◽  
Newborn Rats ◽  
Anaerobic Conditions ◽  
Newborn Rat ◽  
Carbon 14 ◽  
Liver Glycogen Content ◽  
Old Rats

Pyruvate labeled with carbon-14 was administered intraperitoneally to newborn rats which were subsequently subjected to periods of aerobiosis or anaerobiosis. Expired air was analyzed for carbon dioxide, and blood, liver and carcass were analyzed for pyruvate, lactate, glycogen and total lipids. Small quantities of CO2 were produced anaerobically but this was not derived from the direct decarboxylation of pyruvate. Anaerobiosis resulted in a five-fold increase in blood lactate. The liver glycogen content of 10–24-hr-old rats treated anaerobically was only 10% of that of those kept in oxygen. The premature and newborn rats were apparently unable to mobilize glycogen in response to anoxia. The amounts of liver or carcass lipids were not significantly different after aerobic or anaerobic conditions. Lipogenesis occurred anaerobically at a rate not greatly different from that observed in aerobic conditions. In contrast, the data suggest that the utilization of lipids is reduced by anaerobiosis. No gross changes were found that could entirely explain the ability of neonates to survive prolonged oxygen deprivation but part, at least, of the energy for survival was provided by accelerated glycolysis.

Identification of Natural and Synthetic Polyisoprene Vulcanizates by the Carbon-14 Dating Technique

1977 ◽  
Vol 50 (4) ◽  
pp. 819-827 ◽  
Author(s):  
H. Y. Chen
Keyword(s):  
Natural Rubber ◽  
Radiocarbon Dating ◽  
Radioactivity Measurement ◽  
Limited Data ◽  
Carbon 14 ◽  
Synthetic Rubber ◽  
Natural And Synthetic

Abstract The idea of using the radiocarbon dating technique for the differentiation of natural rubber from synthetic rubber is novel and has never been tested before experimentally. The experiments were designed to demonstrate the feasibility of the approach rather than to perfect the technique. With the limited data gathered here, it was shown that the radiocarbon dating technique furnishes results with accuracy quite satisfactory for the analysis of gum rubbers. For the cured samples, the accuracy is reduced mainly by the errors introduced from steps other than that of the radioactivity measurement. A further reduction of the accuracy results if the age of the natural rubber in the stock is not known. We conclude that the technique is feasible and yields results of an accuracy which is probably the best ever achieved by any known technique.

scholarly journals Dependence of Adhesion Properties on Blend Ratio of Ethylene-Propylene-Diene Rubber/Standard Malaysian Rubber Blend Adhesive

2013 ◽  
Vol 2013 ◽  
pp. 1-6
Author(s):  
B. T. Poh ◽  
J. Lamaming ◽  
G. S. Tay
Keyword(s):  
Dilution Effect ◽  
Peel Strength ◽  
Adhesion Properties ◽  
Blend Ratio ◽  
Ethylene Propylene ◽  
Ethylene Propylene Diene Rubber ◽  
Poly Ethylene ◽  
Pet Film ◽  
Blend Ratios ◽  
Diene Rubber

Viscosity, tack and, peel and shear strengths of ethylene-propylene-diene rubber (EPDM)/standard Malaysian rubber (SMR L) blend adhesive were studied using various blend ratios of the two rubbers, ranging from 0 to 100% EPDM. Coumarone-indene resin, toluene, and poly(ethylene terephthalate) (PET) were used as the tackifier, solvent, and coating substrate, respectively. The tackifier content was fixed at 40 parts per hundred parts of rubber (phr). A SHEEN hand coater was used to coat the adhesive on PET film at four coating thicknesses, that is, 30, 60, 90, and 120 µm. The viscosity and adhesion properties were determined by a Brookfield viscometer and a Lloyd Adhesion Tester, respectively. Results show that the viscosity, loop tacks and peel strength of blend adhesives decrease gradually with increasing % EPDM. This observation is attributed to dilution effect and lowering in wettability and compatibility. Shear strength, however, passes through a maximum at 20–40% EPDM blend ratio, an observation which is ascribed to culmination of cohesive strength at the optimum EPDM blend ratio. Increasing coating thickness increases the adhesion properties in all blend ratios in this study.

SPECIES DIFFERENCES IN STEROIDOGENESIS FOLLOWING THE IN VITRO INCUBATION OF DECAPSULATED TESTES

1977 ◽  
Vol 86 (4) ◽  
pp. 851-864 ◽  
Author(s):  
B. de la Torre ◽  
M. Hedman ◽  
E. Diczfalusy
Keyword(s):  
Guinea Pig ◽  
Guinea Pigs ◽  
Species Differences ◽  
Fold Increase ◽  
Human Testis ◽  
Experimental Conditions ◽  
Marked Rise ◽  
Carbon 14 ◽  
Major Increase

ABSTRACT Decapsulated testes of rats, guinea pigs and rabbits were incubated with or without labelled precursors and the steroids formed under various experimental conditions were analysed. Also a decapsulated human testis was incubated with labelled acetate. Cholesterol, testosterone and androstenedione were isolated in a radiochemically homogeneous form following the incubation of carbon-14-labelled sodium acetate with decapsulated testes of all 3 animal species. No other labelled steroid was detected following the incubation of rat testes. Guinea pig testes also converted labelled acetate to pregnenolone. Rabbit and human testes converted labelled acetate to cholesterol, pregnenolone, dehydroepiandrosterone, androstenediol, testosterone and androstenedione. When decapsulated testes of rats, guinea pigs and rabbits were incubated with carbon-14 labelled pregnenolone as a precursor, radiochemically homogeneous progesterone, 17-hydroxypregnenolone, dehydroepiandroster-one, androstenediol, androstenedione and testosterone were isolated in each experiment. Using radioimmunoassay techniques, preformed steroids together with steroids formed from endogenous precursors were analysed following the incubation of rat, guinea pig and rabbit testes in the absence and in the presence of human chorionic gonadotrophin (HCG). Marked (seasonal?) variations were observed between the results of experiments conducted at different times. Incubation of guinea pig testes in the absence as well as in the presence of HCG resulted in a major increase in pregnenolone levels. No such finding was encountered when rat and rabbit testes were incubated. The addition of HCG resulted in at least a 10-fold increase in testosterone formation by the testes of all three species. The addition of HCG to the incubation medium induced a marked rise in dihydrotestosterone levels in the rabbit testes but had no effect whatsoever on the levels of this steroid in guinea pig testes. It is concluded that considerable species differences exist in the steroid metabolism of decapsulated testes incubated in vitro.

Pyrrole Copolymers with Enhanced Ion Diffusion Rates for Lithium Batteries

1997 ◽  
Vol 496 ◽  
Author(s):  
Paul Calvert ◽  
Zack Gardlund ◽  
Trey Huntoon ◽  
H. K. Hall ◽  
Anne Padias
Keyword(s):  
Diffusion Coefficient ◽  
Lithium Batteries ◽  
Fold Increase ◽  
Anion Transport ◽  
Ion Diffusion ◽  
Discharge Characteristics ◽  
Anion Diffusion ◽  
Relaxation Measurements ◽  
Current Densities ◽  
Diffusion Rates

ABSTRACTCopolymers of pyrrole with a polyether-substituted pyrrole were tested as cathodes for lithium batteries. The charge and discharge characteristics showed that anion transport was much faster in the copolymer than in polypyrrole. As a result these electrodes store and release much more charge at higher current densities but are similar to polypyrrole at low currents. Pulse and relaxation measurements of the ion diffusion showed that this difference was due to a ten-fold increase in the anion diffusion coefficient.

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