bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Liquid Rocket Fuels and Oxidizers on Elastomeric O-Ring Seals
Authors: Bellanca C. L. , Salyer I. O. 
Published: February 2011

Abstract
O-ring seals of selected elastomeric and compliant materials were evaluated for resistance to liquid rocket fuels and oxidizers in a simulated end-use test. Oxidizers were nitrogen tetroxide, chlorine trifluoride, and 90 per cent hydrogen peroxide; fuels were mixed hydrazines, pentaborane, and Hybaline A-5. Tests were made at 73° F with all fluids; further, the effect of elevated temperature (160° F) on seals was evaluated in nitrogen tetroxide, hydrogen peroxide, and mixed hydrazines. At 73° F only polytetrafluoroethylene was resistant to all of the fluids; however, elastomeric materials were found which were satisfactory for specific fuel or oxidizer systems. Butyl and ethylene propylene rubber appear satisfactory for long term storage in the presence of mixed hydrazines and Hybaline A-5. The fluorocarbons appeared best of the elastomeric materials for use with pentaborane and hydrogen peroxide.
Elastomers for Use in Heart Valves
Authors: Raible D. A. , Keller D. P. , Pierie W. R. , Koorajian S. , Partridge E. G. 
Published: February 2011

Abstract
Approximately 0.1 per cent of silicone rubber balls from the estimated 18,000 implanted Starr-Edwards heart valve prostheses have been found to be variant. This material variation has initiated investigations of present material and accelerated the search for new and improved elastomers. Descriptions of various types of artificial heart valve prostheses, environmental conditions, design requirements and test apparatus are presented. Variant balls exhibit external physical damage by surface grooves and splits. Internal changes and discolorations from absorbed lipid materials have also been observed. Variant silicone rubber balls have poor physical properties compared with nonvariant or non-implanted balls. This reduction lowers the resistance to damage. The engineering laboratory evaluation program of elastomeric materials includes the compilation of test data on balls molded from silicone, butyl, ethylene propylene, polybutadiene and chlorohydrin rubbers. Butyl and polybutadiene rubbers were selected to demonstrate the extremes of the resilience spectrum with respect to the hydraulic performance of the ball type prosthesis. Compounds with low resilience for less ball rebound appear to be advantageous in this application To date, butyl rubber has exhibited excellent wear resistance in laboratory durability testers.
Elastomers in the Human Body
Authors: Falb R. D. , Grode G. A. , Leininger R. I. 
Published: February 2011

Abstract
Several problems arise when polymeric materials are placed in the body: (1) damage to the body such as blood coagulation, hemolysis, and protein denaturation, and (2) degradation of the polymers caused by exposure to the body's enzyme system. Several methods are presented in this paper to produce elastomeric materials that do not cause clotting of blood. This is accomplished by chemically binding a mucopolysaccharide (heparin) to their surfaces. The materials that have been treated in the work are silicone rubber, polyester polyurethan rubber, natural rubber, and butadiene pyridine rubber.
Resistance of Silicone Rubbers to Body Fluids
Authors: Boone J. L. , Braley S. A. 
Published: February 2011

Abstract
Certain medical grades of silicone rubber have been found to be very useful for implantation in the extremely demanding environments encountered inside man's body. These materials are used in plastic surgery as replacement for soft tissue and cartilage. They are also useful as prostheses, tubes or devices that are used in contact with various body fluids, such as bile, stomach acids, urine and blood. Fairly recently there have been a few instances of failures of artificial heart valves prostheses, which have been caused by an absorption of fatty materials into silicone rubber components of these prostheses. These failures are a matter of great concern, and efforts are being made to study this problem with the hope of finding some solution.
Hydrolytic Stability of Urethan Elastomers
Authors: Ossefort Z. T. , Testroet P. B. 
Published: February 2011

Abstract
Data have been presented bearing on the hydrolytic stability of a wide variety of urethan elastomers (Table III). It has boon shown that polyester based elastomers are considerably more susceptible to hydrolytic attack than polyether elastomers up to 158° F. The nature of the attack and results obtained are profoundly influenced by the temperature. At temperatures of 120° F and above the attack appears to be a “simple” hydrolysis consisting of scission of main chain ester groups resulting in reversion of the rubber. In this case aging over water and in water are similar. At temperatures below 120° F the attack cannot be rationally treated without considering the part played by fungi. In this case exposure over water yields drastically different results from immersion— the former being more severe by several orders of magnitude. Typically the attack over water involves a short term (two to three weeks) cracking of stressed or unstressed specimens and a gradual softening which takes place over a period of many months. The cracking seems to be connected with fungus attack. Resistance of polyesters to hydrolytic attack can be improved by the use of additives such as diisocyanates, fungicides, and carbodiimides. The latter are most useful and apparently scavenge the carboxylic acid resulting from hydrolytic breakdown of the polyesters thereby preventing autocatalysis. Their ability to react with carboxylic acids under these mild conditions has been reported. Differences among polyesters not only in inherent resistance to hydrolysis but also in response to inhibition are found. As has been seen the early cracking can be eliminated by use of sulfur cures, or inclusion of a fungicide but only at the expense of reduced resistance at 158° F. Accelerated tests have been shown to correlate reasonably well with outdoor exposures. Results on unstressed specimens correlate with the 158° F test while the stressed specimens yield results similar to exposure at 95 per cent R.H. and 100° F. Not all linear polyesters are susceptible to hydrolysis such as is poly (ethylene propylene adipate). The terephthalate polyesters, poly (ethylene terephthalate) and poly(1,4 cyclohexane diearbinyl terephthalate), have been exposed in the form of thin films over water at 158° F for 14 months and over water at 95 per cent R.H. and 100° F for 23 months without visible signs of deterioration. They are apparently stabilized by the presence of the aromatic rings or steric factors or a combination of these. In conclusion it must be said that although some progress has been made in protecting polyester urethan elastomers from hydrolytic failure under tropical and high humidity conditions, the problem has only partially been solved.
Abrasion Resistance and High Speed Tensile Strength of Elastomers
Authors: Ecker Ruprecht 
Published: February 2011

Abstract
In earlier communications, we defined abrasion, especially of tires, as a thermal-oxidative process caused at high velocity of mechanical rupture. Other authors (e.g., Schallamach, Boggs, Zapp etc.), with theoretical and experimental tests, prove the importance of viscoelastic behavior as a characteristic property for abrasion. The results of experiments on six elastomers (NR, IR, BR, SBR, IIR, and EPT) compared in tire tread compounds are communicated and discussed in the present work. Tensile strength was determined over a temperature range of 20° to 140° C at deformation speeds of 10 to 20,000 % elongation per second. Forced, non-resonant vibrations were used to determine viscoelastic properties, e.g., resilience, storage modulus, and loss modulus. As abrasion is a consequence of frictional processes, coefficients of friction, dependent on temperature, were measured on dry, wet, and frosty asphalt/fine concrete track. The apparatus is briefly described. From these test results, an empirical relation established between abrasion, friction, viscoelastic properties, tensile strength at high speed and temperature allows one to predetermine the abrasion behavior of a vulcanizate in the laboratory.
Dynamic Mechanical Properties of Cross-Linked Rubbers. I. Effects of Crosslink Spacing in Natural Rubber
Authors: Ferry John D. , Mancke Ralph G. , Maekawa Etsuji , Oyanagi Yasuji , Dickie Ray A. 
Published: February 2011

Abstract
Complex shear compliances of five samples of natural rubber crosslinked by cumyl peroxide and three samples crosslinked by sulfur, covering a broad range of average crosslink spacing, have been measured over a frequency range of 0.1 to 1000 cps and a temperature range from −18 to 55° C. The data were all reduced to 25° C by shift factors calculated from an equation of the WLF type. In the transition zone of frequencies, the viscoelastic functions were closely similar; the loss tangents of the cumyl peroxide vulcanizates were identical within experimental error, and those of the sulfur vulcanizates were shifted somewhat to the left on the logarithmic frequency scale with increasing degree of vulcanization. In the rubbery zone, the losses persisted to much lower frequencies than could be expected from configurational rearrangements within individual strands on the basis of current molecular theories, reflecting slow relaxation mechanisms whose presence has also been deduced from other measurements. The magnitude of the loss tangent at a given frequency in this zone (e.g., 1.6 cps) increases substantially with the average spacing between crosslinks in both cumyl peroxide and sulfur vulcanizates. The possible role of trapped coupling entanglements as a source of the slow relaxation mechanisms is discussed.
Note on Conductivity and Modulus of Carbon-Black-Loaded Rubbers
Authors: Payne A. R. 
Published: February 2011

Abstract
Electrical conductivity and dynamic shear modulus measurements were made simultaneously on carbon black-filled natural rubbers. G′, the in-phase shear modulus, and the electrical conductivity, G, were shown to vary in an approximately similar way as the amplitude of dynamic oscillation was increased. Both G′ and C altered sigmoidally from a high value at low amplitudes of oscillation to very much reduced values at high amplitudes of oscillation. Recovery curves for conductivity were shown to be parallel with respect to the logarithm of the time, even though the initial deforming amplitudes varied widely.
Structure of Ethylene Propylene Dicyclopentadiene Terpolymers
Authors: Cooper W. , Eaves D. E. , Tunnicloffe M. E. , Vaughan G. 
Published: February 2011

Abstract
Terpolymers of ethylene, propylenc and C14-dicyclopentadiene have been compared with model compounds to determine the structure of combined termonomer units. Reactions with iodine monochloride, bromine and the infrared spectra of the terpolymers indicate that dicyclopentadiene polymerizes at the 9,10 double bond without ring-opening or disproportionation.
Accelerated Oxidations of Polyisoprene. II. Effects of Hydrazines, Sulfur Compounds, and Phenyl-β-Napthylamine in Solution
Authors: Mayo Frank R. , Heller J. , Walrath R. L. , Irwin Katherine C. 
Published: February 2011

Abstract
At concentrations of 0.1 to 1 mM, phenylhydrazine causes marked decrease in viscosity of polyisoprene solutions in a few minutes at 50° C (see section II). This effect requires the presence of oxygen but no preoxidation of the rubber. Two molecules of oxygen are absorbed and about one fifth to one tenth of a chain is cleaved per molecule of phenylhydrazine added. The reaction is essentially complete within 20 min. This fast reaction is not much affected by the presence of antioxidants but results in the formation of some material (possibly phenolic) which reduces the effectiveness of other prooxidants. 1,1 -Dimethylhydrazine and 1,2-diphenylhydrazine, unlike phenylhydrazine, have slow but sustained effects. Hydrazine monohydrate is intermediate in its action. Investigation of the effects of several sulfur compounds on polyisoprene solutions brought out some striking effects and a need for further work. p-Thiocresol is a strong prooxidant for our polyisoprene solutions at concentrations below 0.2 mM. At higher concentrations, induction periods occurred with some, but not all, samples and could be shortened by the addition of t-butyl hydroperoxide. Di-p-tolyl disulfide was somewhat less active, but its effect increased regularly with its concentration. Other aryl thiols and disulfides had similar activity but benzyl derivatives did not. At low concentrations, benzene sulfinic acid and p-toluene sulfinic acid are as strong prooxidants as the aryl thiols; at high concentrations they are more active but short lived. A few other sulfur compounds or combinations had no interesting prooxidant properties. In contrast to results on polyisoprene, aryl thiols and sulfinic acids had little effect in preliminary tests in promoting the oxidation of cyclopentene and methyl-cyclohexene. The effects of a common rubber antioxidant, phenyl-β-naphthylamine, alone and in combination with various prooxidants, were followed by oxygen absorption and viscosity changes. The effects are complex; there are indications of both catalytic and anticatalytic effects, and of both scission and crosslinking. The results are most useful in showing the potential of the method for future work on understanding and comparing effects of antioxidants.
Accelerated Oxidations of Polyisoprene. IV. Effects of Sulfinic Acids on Bulk Natural Rubber
Authors: Mayo Frank R. , Parkinson D. B. 
Published: February 2011

Abstract
This paper shows that benzene and toluene sulfinic acids cause rapid disintegration of a cured tread stock in the presence of air at 30° C, a slower reaction in the absence of oxygen. The sulfinic acids also cause rapid solution of smoked sheet in o-dichlorobenzene at 30° C in the absence of oxygen to give mobile solutions.
Vulcanization of an Ethylene Propylene Diene Rubber
Authors: Frensdorff H. K. 
Published: February 2011

Abstract
This study concerns the sulfur vulcanization of EPT with dithiocarbamate accelerators. The reactions undergone by the accelerators are equivalent to those found during natural rubber or SBR vulcanization; TMTM and TMTD are almost completely converted to ZDMC. During vulcanization about 50% of the double bonds are saturated, and approximately one crosslink is formed for each two double bonds initially present. Equilibrium swelling measurements before and after mercaptan cleavage were used to determine the concentration of all crosslinks and that of monosulfide ones as functions of vulcanization conditions. Vulcanization kinetic were followed by Monsanto rheometer measurements. The process takes place in two stages: an initial fast reaction representing vulcanization by the primary accelerator, followed by a slower first order reaction due to acceleration by ZDMC. Accelerator, sulfur, and zinc oxide concentrations have little effect on the rate constants which, however, are nearly proportional to polymer unsaturation. The rate constants approximately double with each temperature rise of 10° C.
Radiotracer Studies of Carbon Black Surface Interactions with Organic Systems. I. Experimental Approach and Initial Results from Chemisorption and Vinyl Polymerization Studies
Authors: Deviney Marvin L. , Whittington Lawrence E. 
Published: February 2011

Abstract
Radiotracer techniques have been applied to the study of interactions of carbon black surface functional groups with two chosen organic systems. The basic reaction mechanisms demonstrated in this study may have implications in elastomer reinforcement. Direct radiochemical evidence supports the conclusions of Hallum and Drushel (based on less direct polarographic data) that surface quinonic groups exhibit hydrogen abstraction activity toward tertiary hydrogens in paraffinic hydrocarbons. Studies on the system carbon black and styrene using tritium radiotracer have provided direct evidence that phenolic hydrogens participate in the polymerization acceleration and graft polymer formation reaction and are transferred to the growing polystyrene chains as postulated by Donnet. Several methods have been developed for specifically labelling certain oxygenated functional groups on the carbon surface with tritium and for tritium labelling carbon black in aromatic hydrogen positions. The techniques developed in this work and the basic reaction mechanisms derived will permit this investigation to be extended into a radiochemical study of carbon black surface interactions with elastomer related systems of interest to the rubber industry.
Radiochemical Determination of Low Unsaturations in Polyisobutene
Authors: McGuchan R. , McNeill I. C. 
Published: February 2011

Abstract
A radiochemical technique involving the use of 36C1 has been described previously for the measurement of butyl rubber unsaturations. This method has now been applied to the estimation of the much lower concentration of double bonds present in polyisobutene prepared by the cationic polymerization of isobutene at a low temperature. The nature of the reaction of polyisobutene with radiochlorine in the absence of air is examined, and the experimental results are discussed in relation to present theories of the mechanisms of chain termination in cationic polymerization.
Pyrolysis Gas Chromatography of Natural Rubber and Synthetic Polyisoprene
Authors: Jernejčič M. , Premru L. 
Published: February 2011

Abstract
Pyrolysis gas Chromatographic isothermal and temperature programed separation of volatile components of unvulcanized natural rubber and synthetic polyisoprene was made on P-E columns Q and U. Besides identifications, relative quantitative differences between pyrolysis degradations of natural rubber and synthetic polyisoprene in pyrolysis temperature range 550°–750° C were established. It was found that the method was not suitable for an analogous study of vulcanized samples.
Determination of 1,4 and 3,4 Addition in Polyisoprenes by Rapid Pyrolysis and Vapor Phase Chromatography
Authors: Vacherot Monique , Marchal Jean 
Published: February 2011

Abstract
These results indicate that, after calibration, this technique can be used to determine the ratio of 1,4 and 3,4 addition in polyisoprenes where the arrangement of monomer units is the same as the polymers used here. This limitation depends on study of other specimens which will show whether sequence distribution has any effect on the results of pyrolysis.
Method for Structural Characterization of High Polymeric Networks by an Osmotic Pressure Technique
Authors: Seeley R. D. , Rand P. B. 
Published: February 2011

Abstract
An apparatus was designed to measure the osmotic pressure of solvent-polymer systems. The method is unique in that semirigid polymers may be incorporated as the solute component without specimen fissures occurring from excessive solvent dilative action. The advantages of this technique are: high polymeric materials both elastomeric and plastic can be structurally characterized by the same technique; the calculated effective molecular weight of the polymer network will reflect a value consistent with the polymer's performance characteristics; and the method is only restricted to lyophilic polymer—solvent systems.
Aspects of Friction and Wear of Tires Arising from Deformation, Slip, and Stresses at Ground Contact
Authors: Savkoor A. R. 
Published: February 2011

Abstract
The role of tread patterns in adhesion on wet roads is emphasized. Tread patterns cause the stress distribution in the area of contact to be wavy and variable both in time and space. Deformation of an inflated tire against a hard flat surface induces a symmetrical and inwardly directed shear stress distribution at the ground contact. Shear stresses have been calculated with certain simplifying assumptions. Apart from the importance of cornering and stability of automobiles, study of a tire set at a slip angle is also important to wear, because high temperatures prevail at the tread surface. Forces developed on wet road surfaces are very low; this leads to use of a high hysteresis tread rubber to give additional friction on such surfaces. Tests carried out elsewhere at high speeds on roads sprayed with water have been of limited value in evaluating the hysteresis component of friction resulting from deformations since change in tread properties resulting from unknown contact temperatures due to surface heating was not considered. Measurements of cornering force on two tires with glass plate apparatus at a speed of only 4.5 cm/sec on dry and lubricated surfaces indicate that the contribution due to hysteresis can be appreciable. Finally, theories explaining the mechanism of wear occurring at the contact between rubber and a hard surface are discussed.
Friction and Viscoelastic Properties of Polymeric Solids
Authors: Ludema K. C. , Tabor D. 
Published: February 2011

Abstract
When a hard slider slides over a rubber surface, there is a close relation between sliding friction at various speeds and temperatures and viscoelastic properties of the rubber. If friction is due to an adhesion mechanism this may be explained in terms of the way in which area of contact A and shear strength s vary with speed and temperature. Area of contact is determined by the elastic modu us of the rubber; during sliding the deformation process is a relatively low frequency one. In contrast, shear strength s involves very high strain rates in a thin surface layer; this corresponds to a very high frequency process. By combining these two effects the observed friction behavior may be explained. Behavior of polymers below their glass transition temperature is very different. Correlation between sliding friction and various viscoelastic peaks is not at all strong. On the other hand, conventional viscoelastic data correlates well with rolling friction. This shows that high local pressures at the contact regions do not substantially change the viscoelastic characteristics. In sliding, however, there are very high shear strains in the surface and appreciable tearing and transfer of polymer; presumably these violent deformations, although in themselves speed and temperature dependent, bear little relation to deformation processes involved in conventional low strain viscoelastic studies. The good correlation with rubber suggests that, even at the high strains involved in sliding, slip of chain segments over one another still remains the basic mechanism of shear. With PTFE, sliding friction shows a dependence on speed and temperature which resembles a viscoelastic peak. However, it is probable that this refers to gliding of crystallites of PTFE over one another where the effective strains are enormous and not to conventional viscoelastic peaks determined under conditions where strains are very small. Apart from its bearing on friction studies the work described in this paper suggests that more information is needed on viscoelastic properties of polymers at high pressure and at large strains.