bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Casting Solvent on the Mechanical Properties of a Styrene-Butadiene-Styrene Block Copolymer
Authors: Fielding-Russell G. S. 
Published: February 2011

Abstract
The tensile mechanical properties of a number of well characterized solution-cast styrene—butadiene-styrene block copolymer systems are reported within the strain range of 0&lt;ε≤5.0. It was found from the results of repeated stretching experiments (up to 100%) at room temperature that polymers cast from solvents for polystyrene or from solvents for both polystyrene and polybutadiene showed lower stresses on each cycle whereas the stress levels for the polybutadiene solvent-cast sample remained essentially constant. The polystyrene solvent-cast and polystyrene/polybutadiene solvent-cast samples exhibited a yield at ε≈0.3. No “yield” was apparent with the polybutadiene solvent-cast sample. The explanation for these behaviors lies in the material of the continuous phase. When the continuous phase is polystyrene there will be long-time recovery after the yield and consequently the system will be left under residual stress so that lower strains are observed on subsequent straining. When polybutadiene is the continuous phase (a phase inversion) no such yielding is apparent, the form of the stress-strain curve is that of an elastomeric material, and hence the repeated stress-strain curves are practically superposable. It was concluded that the low strain region is governed by the material of the continuous phase. From the viscoelastic measurements it was found that at 1.0≤ε≤6.0 the values of the modulus-temperature dependencies were comparable to that given by polystyrene and that the linearity and the slopes of plots of the logaT as a function of temperature were indicative of a glassy and, moreover, a polystyrene response. It was concluded that the strain region 2.0≤ε≤5.0 is governed by the polystyrene content, whether it be in the continuous phase or not. These results, together with certain proposed model structure, are discussed with the available literature.
An HF-Nickel-R3Al Catalyst System for Producing High Cis-1,4-Polybutadiene
Authors: Throckmorton M. C. , Farson F. S. 
Published: February 2011

Abstract
A relatively new, high cis-1,4-polybutadiene and a novel trialkylaluminumnickel-HF catalyst system have been described. This polybutadiene is unique in that it possesses high tack and has exceptionally good processing qualities; the carbon black-loaded and cured rubber possesses good static and dynamic properties. The catalyst system is very effective for producing high molecular weight rubber, suitable for oil extension, and the molecular weight can be controlled by adjusting 1) HF to R3Al ratio, 2) total catalyst concentration and/or 3) polymerization temperature.
An Improved Wire Adhesion Test Method
Authors: Hicks A. E. , Chirico V. E. , Ulmer J. D. 
Published: February 2011

Abstract
A new type of wire adhesion test method has been developed and has been compared to the conventional ASTM (D-2229) method on the basis of both accuracy and precision. The extent to which the ASTM slot type method can bias adhesion measurements by concentrating stresses at the leading edge of the wire-rubber interface has been demonstrated and is in agreement with the findings of other investigators. No such limitation was found with the CSRC method. In terms of precision, the ASTM and CSRC methods were found to be comparable, but the CSRC method was found to be more sensitive to differences in adhesion. The new method was used to show that carbon blacks with higher levels of EM surface area, unit form factor, porosity, and volatile content increased wire adhesion in a NR-sulfur compound, unaged and tested at room temperature. The effects of EM surface area and unit form factor became more important when the compounds were aged severely and tested at 212° F. Increased porosity and volatile content improved adhesion unaged at room temperature, but when adhesion was tested hot and aged, the quality of the rubber deteriorated and adhesion was lowered as the levels of these variables increased. Carbon black loading and type are important in a natural rubber recipe in developing good levels of wire adhesion at various test conditions: first, by altering the rate of vulcanization in a direction that favorably affects the competing reactions of the rubber and brass for sulfur and second, by increasing the reinforcement of the rubber, particularly at high temperatures.
A Rapid Quantitative Method for Measuring Ozone Cracking and Its Use in Outdoor Dynamic Testing
Authors: Veith A. G. 
Published: February 2011

Abstract
A fairly rapid quantitative technique for measuring the cracking damage done to rubber by ozone has been described. The method consists of microscopic measurement of the length and width of selected ozone cracks. The product of the “average” length and width is termed the “severity of ozone cracking” and is abbreviated, SOC. The SOC value for a specimen is approximately 2 times the void area in arbitrary units. The use of the SOC technique in conjunction with an outdoor dynamic ozone test showed how various antiozonants perform in NR, SBR, and OE-SBR both with and without wax. Some effects of the amount and type of extending oil and of wax melting point are illustrated. Weather plays an important role in regard to ozone attack especially for wax containing compounds. During the warmer months higher melting waxes perform better in natural and OE-SBR while higher melting waxes perform slightly poorer in non-oil extended SBR. Good correlation was found between the outdoor flexing tests and service type outdoor tire tests carried out on an outdoor wheel. Some of the ramifications of this type of testing are pointed out.
The Tensile Strength of Glass Yarn in Rubber. II. The Effects of Normal Humidities
Authors: Gregg R. A. 
Published: February 2011

Abstract
The resinous impregnant in glass yarn influences the stability of the yarn. Some glass yarns suffer tensile degradation on storage and/or vulcanization at high humidities. One type of glass yarn was exposed in atmospheres over the range 0–88% relative humidity at 73° F for times up to 400 days. Tensile losses of 30% or more can occur on storage of the glass yarn at the humidities in the upper end of the range. This loss is permanent as even vigorous drying at high temperatures will not restore the tensile. Under dry conditions the yarn has excellent storage stability. Furthermore, after vulcanization even into thin composites, the glass yarn shows only a small permanent loss of tensile under moisture conditions that would seriously degrade the yarn in a package. An increased degree of vulcanization of the rubber slightly increases the tensile strength of the composite. In addition to its permanent degradative action in long-term exposure, water has a phenomenological effect of reducing glass composite tensile by its presence. A tensile sensitivity to moisture index is suggested and used to characterize the glass yarn. This tensile loss is recoverable by drying but some of the water is bound very tightly. Thin composites do not give up all of the water in 150 days over Drierite® as shown by the fact that more vigorous high temperature drying leads to a further increase in tensile strength. Tensile strength at 300° F is about 25% lower than at 73° F at any moisture content. Higher moisture contents lead to lower absolute tensiles. Tensile values are detailed for conditions that might exist during cure or in a product running at a high temperature. The high temperature incurred tensile reductions from a standard tensile are significant and should be considered in designing products. The detailed observations apply only to this particular glass yarn but the principles and methods are applicable in the evaluation or development of any glass yarn.
Rubber—Black Interaction Influence on Cure Level of Vulcanizates
Authors: Brennan J. J. , Lambert D. H. 
Published: February 2011

Abstract
The crosslink density of vulcanizates has been quantitatively investigated using swelling measurements (Vr) of compounds of cis-1,4-polybutadiene reinforced with N242, N326, or N990 (Vulcan 6H, Regal 300, Sterling MT). Crosslink density in both filled and unfilled stocks is shown to be related to the molar concentration of the curatives in the unbound rubber phase of the vulcanizates and not merely to total concentration. The effects of different carbon black loadings and of cure time are demonstrated to be fully describable by the extent of carbon black—rubber interaction, measured by bound rubber; that occurs during mixing and during the induction period of the cure step. Greater rubber-black interaction, whether achieved by higher black level or from higher reinforcing blacks, always yielded vulcanizates of increased crosslink density compared to an identically vulcanized gum control. Calculating curative concentration on the basis of unbound rubber—rather than total rubber—illustrated the expected dependence of crosslink density upon curative concentration and graphically explains the presence of so-called “excess” crosslinks. Implied, also, is one cause for the “scorchy” character of highly reinforcing blacks and the higher modulus obtained with these blacks.
Review of Basic Oxidation Processes in Elastomers
Authors: Shelton J. Reid 
Published: February 2011

Abstract
The early studies of chain scission in the oxidation of rubber by Dr. E. M. Bevilacqua, and his subsequent work on the identification of the various acids, methyl ketones, and other volatile products of the oxidation reaction, have contributed much to our present knowledge of the nature of the processes involved in the oxidation of elastomers. His numerous research publications and review papers represent a significant segment of the world's literature on oxidation and aging of rubber. This introductory paper of the E. M. Bevilacqua Memorial Symposium is a brief review of our present understanding of some of the basic oxidation processes in elastomers. More extensive reviews of various aspects of the subject are available. This review is primarily concerned with the nature of the chemical reactions involved in the oxidation, degradation, and stabilization of elastomers. The mechanism of uninhibited autoxidation (based on model compound studies) will be compared with the more complicated sequence of reactions observed in the retarded autoxidation of elastomers which occurs in the presence of antioxidants. The oxidative degradation of physical properties will be considered in terms of the resultant effect of the two competing processes of chain scission and crosslinking. The role of antioxidants as stabilizers against oxidative degradation will be discussed from the standpoint of the mechanisms by which different types of stabilizers protect elastomers during aging and use.
The Application of Model Reactions to the Oxidation of Polyolefins
Authors: Allara D. L. , Edelson D. 
Published: February 2011

Abstract
Initial attempts have been made using computational techniques to apply model compound reactions quantitatively to the oxidation of ethylenepropylene copolymers by molecular oxygen at 100° C. The oxidations of n-butane, isobutane, and isopentane (the simplest model of a polypropylene repeat unit) were chosen as models and applied to the prediction of rates and products in the low conversion oxidations of squalane and a series of ethylenepropylene copolymers of differing composition at 100°. For simplicity, these initial calculations were done for a low viscosity fluid phase. For externally initiated reactions, where calculated and experimental rates (mostly amorphous, solid phase) could be compared, agreement was usually within a factor of 3–5, with the calculated rates generally too fast. Our results on both self- and externally initiated systems suggest that the effect of phase change, from liquid to amorphous solid, on the overall oxidation rate is not large, except in a few cases where effects such as chemically induced crystallization may be significant in the solid phase. Calculations for externally initiated oxidations predict that the rate of chain scission is proportional to the rate of radical production in excellent agreement with experimental results. Our initial results indicate that small alkane molecule reactions can be applied usefully, at present with limited accuracy, to the oxidation of hydrocarbon polymers.
Oxidation of Photoexcited Elastomers
Authors: Morand Mme J. L. 
Published: February 2011

Abstract
The sensitivity spectrum of elastomers to sunlight (λ≽300 nm), determined by the variation at 30° C of the initial rate of oxidation or chain scissions as a function of the wavelength of incident light, shows several maxima in the near UV. These maxima are approximately equidistant and the space between them differs only slightly (10 to 11.5 nm) according to the polydienes (polyisoprene, polybutadiene, copolymer butadiene-styrene) in the crude or the vulcanized state, whatever may be the curing system. The identified maxima, existing also under vacuum (10−4 Torr), can be due to the presence of some chromophores in the chains. The latter, in absorbing the light during the primary photophysical process, would initiate the degradation. Among different possibilities, an S0→T1 transition of the isolated double bonds, producing free radicals, seems to be the one likely to explain the results. After the initiation, the photoxidation at 30° C and 5 mW/cm2 proceeds like the thermoxidation near 150° C. For a peroxide vulcanized rubber, the kinetics are similar and the rates of oxidation are somewhat faster under the most harmful sunrays than those observed by Bevilacqua at 120° C. Moreover, the chain scissions are a linear function of the oxygen consumed and their ratio is close to the limiting value of about 6 moles of O2 per broken bond, obtained by this author at 140–150° C.
Molecular Theories of Rubberlike Elasticity and Polymer Viscoelasticity
Authors: Shen Mitchel , Hall William F. , Dewames Roger E. 
Published: February 2011

Abstract
The foundation for nearly all the molecular theories of the physical properties of polymers was laid in 1934 when Guth and Mark and Kuhn first recognized the role of configurational entropy of polymer chains. By virtue of ability of their segments to rotate with respect to each other along the chain backbone, macromolecules are capable of assuming a myriad of conformations. It is this long, flexible chain nature of polymer molecules that provides us a link in interpreting the macroscopic physical properties in terms of microscopic molecular dynamics. In this review we shall demonstrate the utilization of conformational statistics in the formulation of molecular theories for two important aspects of the mechanical properties of polymers. The first part deals with the equilibrium elastic response of a crosslinked rubberlike network. A simplified derivation will be given on the basis of the entropic approach. Some of the underlying assumptions will then be examined, and the contribution of internal energy to rubber elasticity scrutinized. The second part describes the transient viscoelastic properties of linear polymers in solution and in bulk. Limitations of the model will be assessed and its applications to experimental data explored. It should be pointed out that a number of reviews are available in the literature both for elasticity and viscoelasticity of polymers. The present work is not an exhaustive review of these fields, but rather concentrates on the more recent developments not previously discussed. The emphasis will be placed upon polymers in the bulk state, although solution properties will be mentioned where appropriate.
Effective Degree of Immobilization of Rubber Occluded within Carbon Black Aggregates
Authors: Medalia A. I. 
Published: February 2011

Abstract
The conclusions of the present work may be summarized as follows. 1. The effective volume of carbon black in rubber, as measured by the low-strain equilibrium modulus, is equal to the true volume of carbon plus about half of the occluded volume of rubber calculated from the DBP absorption of the carbon black. 2. Breakdown of aggregates on incorporation in rubber may diminish the volume of occluded rubber; thus, calculations based on the same modulus data would give a somewhat higher effectiveness factor—perhaps of the order of 0.6, depending on the degree of breakdown assumed. 3. Under non-equilibrium conditions various processes may either raise or lower the measured modulus and (thus) the occluded volume effectiveness factor : (a) At moderate to high strains, strain amplification raises the modulus. (b) At low temperatures, amplification of the rate of strain raises the modulus (relative to that of the gum). (c) In a highly loaded vulcanizate, the secondary network of carbon black raises the modulus measured at low strain and low or moderate temperature. (d) The modulus can be lowered by molecular slippage, especially with thermal blacks, or with graphitized furnace blacks, at elevated temperatures and/or high strains.
Natural Rubber Latex Concentrate Properties and Processibility
Authors: Gorton A. D. T. 
Published: February 2011

Abstract
The concept of latex concentrate processibility and its relation to raw latex properties and proposed chemical stability tests is examined. The KOH number of latex is shown to have only a limited value as a criterion of latex properties. A new test is proposed based on the viscosity behavior on storage of a fully compounded latex. This test is experimentally compared to other proposed tests, raw latex properties, and the influence of various additives. Methods of controlling latex compound viscosity are suggested.
The Impact of Lithium Initiators on the Preparation of Synthetic Rubbers
Authors: Adams H. E. , Bebb R. L. , Forman L. E. , Wakefield L. B. 
Published: February 2011

Abstract
The impact of the lithium initiator system has begun in the rubber synthesis field; it will surely expand into the production of plastics of controlled and desirable structure. Polymers can be designed in both fields with precise structure control for desired processing characteristics and properties. This will become more useful as the concept of domains and heterogeneity is more fully understood and utilized. The system will also lend itself to planned termination by functional groups where the products will have unusual reactivities. Solution polymerization systems should play an increasing role in the production of synthetic rubber. Of course, the emulsion system must be considered in applications where latex itself is desired and in those cases where monomers with functional groups would react with the organometallic initiator. Otherwise, we believe that solution systems will produce rubber with especially desirable properties more cheaply without as much harm to the ecology.
Carbon-13 NMR of Poly(Butadiene)
Authors: Mochel V. D. 
Published: February 2011

Abstract
By using the carbon-13 NMR technique, it is shown that there are no cis-1,4-trans-1,4 linkages in an n-BuLi-catalyzed poly (butadiene). The polymer consists of “blocks” of cis-1,4 units and trans-1,4 units separated by isolated vinyl units. Preliminary evidence suggests this might also be true for other types of 1,3-diene polymerization. Some of the implications of this finding on the mechanism of polymerization are discussed. Tacticity triad distributions are readily determined in poly(butadiene)s with high 1,2 addition contents.
The Synergistic Effect of Natural Rubber on the Crystallization of Lithium Poly(Isoprene)S (Coral Rubber)
Authors: Brock M. J. , Hackathorn Marjorie J. 
Published: February 2011

Abstract
The influence of silver nitrate on the crystallization of poly(isoprene)s has been demonstrated as well as the synergistic effect of natural rubber on the crystallization of lithium catalyzed poly(isoprene). This synergism does not appear to be a “seeding” effect in the strictly definitive sense, since no seed crystals are actually added. In this case a better description of this effect might be cocrystallization where nucleation is promoted by the addition of a quantity of a highly regular similar species. Actually there is a good probability that the nucleating crystals themselves contain segments of the synthetic poly(isoprene). This conclusion is supported by the data shown in Figure 6 for a 50/50 mixture of natural rubber and a noncrystallizable Alfin polymer. The dilato meter curve for this mixture indicates that the 50 per cent non-crystallizable polymer has a slight retarding effect on the induction period for the crystallization of the natural rubber but the crystallization rate of the natural rubber in the 50/50 mixture is quite rapid up to the total volume change expected for natural rubber portion of the mixture. However, in the presence of 50 per cent of a crystallizable lithium poly(isoprene) (also shown in Figure 6), the crystallization rate of this mixture is much slower due to co crystallization. The proposed change from head-tail cis-1,4 addition to tail-head cis-4,1 addition whenever a 3,4 unit is introduced into the polymer chain seems to explain the experimental crystallinity data obtained in these studies. In addition, it raises some questions about the polymerization mechanisms involved and resulting from the orientation of a 3,4 unit being added to the growing end of a polydienyl chain.
Diene Termonomer Type and EPDM Properties
Authors: Baranwal K. C. , Lindsay G. A. 
Published: February 2011

Abstract
The objective of this work was to study the effects of the type of diene termonomer on properties, especially thermal stability and aging, of EPDM polymers. Five different EPDM polymers using ethylidene norbornene (ENB), butadiene (BD), dicyclopentadiene (DCPD), methyltetrahydroindene (MTHI), and 1,4-hexadiene (HD) as termonomers were made at equimolar unsaturation. The same sulfur/accelerator system was used for curing these polymers. In both gum and filled vulcanizates ENB-EPDM is the fastest curing. In gum stocks HD-EPDM is the slowest curing, but is faster than DCPD-EPDM in filled stocks. These polymers, except for BD-EPDM, have about the same initial crosslink densities. Crosslink density and crosslink type analyses indicate that butadiene units in BD-EPDM chains are blocked. For HD-EPDM, both in gum and filled vulcanizates, 50 per cent of original crosslinks are monosulfidic. The other four EPDM vulcanizates have a lower proportion of monosulfidic crosslinks. At 350° F aging temperature, both ENB and HD polymers have ∼65 per cent monosulfidic crosslinks and about the same energy-to-break values (Eb). However, the higher original monosulfidic crosslink content of HD-EPDM does not seem to offer any better aging than for other polymers. DCPD-EPDM at 350° F aging temperature has the same monosulfidic content but increases further at 550° F aging temperature. At 550° F aging temperature almost all the crosslinks are monosulfidic for these EPDM polymers but the total crosslink densities and Eb are very low presumably due to oxidative degradation. Thermogravimetric analysis in N2 shows that these vulcanizates decompose in 800-935° F temperature range. In air, this range is 750-935° F.