bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ozone Attack and Antiozonant Protection of Vulcanized Natural Rubber. A Surface Study by Attenuated Total Reflectance Spectroscopy
Authors: Andries J. C. , Ross D. B. , Diem H. E. 
Published: February 2011

Abstract
This work reports a direct surface analysis of ozonization of vulcanized NR compounds by ATR. On ozonization of a vulcanized NR compound without clay filler or AO a degraded rubber layer, which contains ozonides and carbonyl compounds, is formed on the surface. This reaction is considerably slower than that of raw NR. When clay filler is added, the first effect is a decrease of rubber on the surface and a corresponding increase in the surface concentration of clay. With further ozone exposure, ozonides and carbonyl compounds appear. When a compound containing N,N′-dioctyl-p-phenylenediamine AO is ozonized, a film is seen, which has an ATR spectrum essentially identical to that of the ozonized liquid AO. There is no evidence of ozonized NR products, or of complex reaction products between AO and ozonized NR. These results are consistent with a scavenger or protection-layer mechanism for antiozonant protection.
Scrap Tire Disposal Process
Authors: Crane Grant , Kay Edward L. 
Published: February 2011

Abstract
Experimental results are presented which indicate that scrap rubber vulcanizates, typical of today's tires, can be depolymerized to a product which is essentially a carbon black dispersion in oil. The depolymerization is free radical in nature and requires an efficient chain transfer agent to prevent hardening of the vulcanizate and to increase the rate of depolymerization. The product, termed “Depolymerized Scrap Rubber” (DSR), should be useful, particularly as a rubber compounding ingredient and as a fuel oil extender.
A Master Curve for Amorphous Elastomers Derived from Small and Large Deformations Using Various Instruments
Authors: Nakajima N. , Collins E. A. 
Published: February 2011

Abstract
Dynamic mechanical measurements, stress—strain measurements, and steady-shear measurements made over a range of temperatures and frequencies or deformation rates are used to characterize the viscoelastic properties of raw elastomers. The measurements involve both small and large deformations. It is shown that the results on either butadiene—acrylonitrile (NBR) or butadiene—styrene (SBR) can be reduced to a single master curve. The instruments and ranges covered included Instron stress—strain (0.2–20 in./min; 25–75°C), Instron capillary (100−104sec −1; 100°C), Rheovibron (110 Hz; 23–156°C), Rheometrics (4×10−2−2.6×102 sec−1; 100°C), MTS high speed tester (267-26 700%/sec; 25–97°C), steady-state Mooney (0.05–20 rpm; 25–150°C) and transient Mooney (0.05 rpm; 25–150°C).
Strain-Dependent Dynamic Properties of Carbon-Black Reinforced Vulcanizates. II. Elastomer Blends
Authors: Sircar A. K. , Lamond T. G. 
Published: February 2011

Abstract
The three-dimensional aggregated structure of carbon black in elastomer blends behaves in a similar fashion to that of the individual elastomers. The elastomer seems to act merely as a dispersing medium. The properties of the rubber reflect the structural effects of the filler superimposed upon the elastomer itself. The elastomer molecules no doubt retain their individual characteristics of rotation of bonds which govern the stiffness of the molecule. However, the superimposed carbon-black network exerts the predominant effect, as far as the low-strain dynamic characteristics are concerned. The polymeric medium seems to influence this interaction by determining the magnitude of agglomeration and distribution of black in the phases, but does not have visible influence on the overall characteristics of the carbon-black networks. In this respect blends of two elastomers behave as a single elastomer. The importance of the present work is that the strain-dependent dynamic properties of blends of elastomers are very similar to those of single elastomers. In tires and antivibration applications, the strain imposed is usually less than 10%. More and more blends of elastomers are being used for these applications. The filler structure and its breakdown at these strains have an important contribution to hardness, modulus, and hysteresis of these compounds.
Monomer Sequence Distribution in Ethylene—Propylene Rubber Measured by 13C NMR. 3. Use of Reaction Probability Model
Authors: Carman C. J. , Harrington R. A. , Wilkes C. E. 
Published: February 2011

Abstract
One can measure r1r2 for an ethylene—propylene rubber by determining composition and χ, the ratio of contiguous to isolated propylene units. Our previous determination of χ depended on measuring methine carbon resonances in a 13C NMR spectrum. The χ method based solely on methine peak area measurements is inaccurate. This is not because the χ method is theoretically unsound, but because it is impossible to accurately extract the methine areas, necessary to calculate χ from the complex 13C NMR spectra of ethylene—propylene rubbers. The presence of inverted propylene produces ambiguity in a portion of the methine region. This means the methine areas can be used only to calculate a maximum and minimum boundary for r1r2. Another difficulty in using only methine areas to determine χ arises at propylene levels less than 35 wt%, because the methine areas for contiguous propylene triads become very small and are overlapped by strong resonances from long methylene sequences. We have developed a reaction probability method which accurately accounts for all the resonance areas in a 13C NMR spectrum of an ethylene—propylene rubber instead of restricting the analysis to the tertiary carbon areas. The reaction probability method produces a complete calculated 13C NMR spectrum as a best fit to the observed spectrum. The deduced probabilities provide the following derived quantities: (1) “r1r2”, a measure of monomer sequence randomness, (2) the distribution of methylene sequence lengths, (3) composition, (4) amount of propylene inversion. The probabilities can be used to directly calculate “r1r2”. Or alternatively, the probabilities can be used to calculate the methine carbon areas including the separation of the ambiguous methine area into contiguous and isolated contributions. These areas calculated from the probabilities can then be used to determine χ and the resultant r1r2. The two values for r1r2 are in good agreement, lending credence to the probability analysis. The composition derived from probabilities agrees with other analytical methods such as proton NMR and infrared. The limitation of the method is that we cannot accurately determine the percent propylene inversion. We can only conclude that in the majority of the copolymers of 20 to 60 wt% propylene that we have studied, the concentration of inverted propylene is significant and is between 10 and 40% of the total propylene present. Propylene enriched in carbon-13 could be used to prepare copolymers and perhaps resolve this uncertainty.
Sequence Distribution of 1,4-Polybutadienes
Authors: Tanaka Yasuyuki , Sato Hisaya , Hatada Koichi , Teeawaki Yoshio , Okuda Hiroshi 
Published: February 2011

Abstract
The spin-decoupled 1H NMR and 13C NMR methods were employed for the determination of the cis-trans sequence distribution in polybutadiene. Poly(butadiene-2,3-d2) and cis-trans isomerized polybutadienes were used for the peak assignment and the resonance of methylene protons in cis-trans linkage could be described as an A1B2 system. The dyad and triad sequence distributions of cis-1,4 and trans-1,4 units were determined for isomerized, equibinary, and lithium catalyzed polybutadienes, and polycyclooctadienes. The accuracy of the measurements was also studied comparing the results with those by infrared method.
Use of Power Integrator and Dynamic Stress Relaxometer to Shorten Mixing Cycles and Establish Scale-Up Criteria for Internal Mixers
Authors: Myers F. S. , Newell S. W. 
Published: February 2011

Abstract
The need for increased production from existing internal mixers has required the reduction of cycle times. The shortening of the cycle also enables mixing with less energy. However, the shortened mixing cycle requires closer control. Our ability to successfully shorten mixing cycles and to combine two-step mixes into one-step has been the direct result of the consistent mixing and uniform stock made possible through energy controlled mixing. Energy controlled mixing has worked, because we have had the necessary tools, the Power Integrator and Dynamic Stress Relaxometer. The transition of a new recipe from research and development to production can be slow and difficult. We believe that energy controlled mixing can reduce the shakedown time required to introduce a new recipe into production. It can also allow production problems to be successfully scaled-down for solution in laboratory mixers.
Vulcanization of Butyl Rubber by p-Quinone Dioxime
Authors: Gan L. M. , Soh G. B. , Ong K. L. 
Published: February 2011

Abstract
The vulcanization of butyl rubber by p-quinone dioxime oxidized by red lead and tetrachloroquinone was investigated. The maximum physical effective crosslinking density of the vulcanizates appeared to be when p-quinone dioxime and the oxidizing agent were equimolar. The formation of one physical effective crosslink required one molecule of p-quinone dioxime. Chemical reactions are suggested for the vulcanization steps.
Thermorheological Properties of Carbon Black Filled Elastomers
Authors: Caruthers J. M. , Cohen R. E. 
Published: February 2011

Abstract
A nonisothermal constitutive equation for a thermorheologically simple, linear viscoelastic materials has been developed. The influence of temperature on both the retardation times and the limiting compliance difference has been considered. This general nonisothermal equation can be reduced to previously published results for the creep T-jump experiment. Isothermal creep response was measured for the filled vulcanizates at various levels of strain. At relatively low strains, the true compliance was observed to increase with strain, the initial increase depending upon the carbon black volume fraction and structure. This increase in compliance was attributed to a breakdown of the carbon black network. A reversal of this trend at much larger levels of deformation was associated with orientation of the rubber chains. The creep rate at 300 seconds depends primarily on the level of strain, independent of the carbon black structure or loading. The apparent activation energy was determined by creep T-jump at various levels of stress for two series of filled compounds and an unfilled gum elastomer. For the filled materials, the activation energy decreased as the level of applied stress was increased. For example, the apparent activation energy of a SBR-1500 vulcanizate filled with 80 phr of N347 carbon black decreased from 167 to 71 kJ/mole as the applied stress was increased from 0.041 to 1.88 MPa. The activation energy at low stresses is a function of the carbon black volume fraction and structure. The apparent activation energy of the unfilled gumstock was 54 kJ/mole, independent of the level of deformation. The apparent activation energy of the filled vulcanizates approached that of the gumstock as the stress increased. The T-jump results and the isothermal data suggest the presence of two deformation mechanisms for the filled materials: (1) deformation of the carbon black network with an apparent activation energy dependent upon the loading and carbon black structure and (2) deformation of the rubber matrix surrounding the carbon black aggregates. At small deformations the first process is the rate controlling viscoelastic process and at large deformations the second process dominates. At intermediate levels of applied stress both mechanisms contribute to the deformation of the filled compounds.
Effect of Curing Systems on Selected Physical Properties of Natural Rubber Vulcanizates
Authors: Studebaker Merton L. 
Published: February 2011

Abstract
Selected physical tests were made on natural rubber vulcanizates prepared with six levels of each of six different curing systems. These combinations produced different types of crosslinks which were subjected to analysis using a combination of swelling measurements and lithium aluminum hydride reduction analyses. The effect of crosslink type or length was reflected in stress-strain measurements. One might reasonably look to crystallization measurements on such vulcanizates for a more complete explanation of the effects of crosslink type on stress-strain measurements. The ability of polysulfide crosslinks to exchange to form new links as the sample is strained should also be examined. When subjected to stress, especially when hot, polysulfide crosslinks are more susceptible to rupture than monosulfide or carbon-to-carbon crosslinks. This crosslink rupture may or may not be compensated for by subsequent formation of new polysulfide or monosulfide crosslinks in a deformed state. Under suitable experimental conditions, as in our compression set measurements, no net change in total crosslinks may take place. Under sufficiently severe test conditions, as in our blowout tests, degradation is severe and total crosslinks measured by swelling decrease. Under some circumstances, it is possible to follow changes in both the quantity and type of crosslinks by the analytical methods used in this study.
Polymerization of Chloroprene II. Role of Dimers in Thermal Polymerization
Authors: Leeming P. A. , Lehrle R. S. , Robb J. C. 
Published: February 2011

Abstract
The results in this paper indicate that the bulk thermal polymerization of chloroprene at 35° is in fact a polymerization of chloroprene dimers, and the rate measurements indicate that little or no monomer adds during the propagation process. Since DPPH does not inhibit the dimerization process but inhibits polymerization, it is tempting to conclude that the polymerization is a free-radical addition process, and this idea is to some extent supported by the retarding influence of some other free-radical inhibitors. On the other hand certain features of the polymerization of bulk dimers are difficult to reconcile with a simple free-radical chain mechanism, and it is considered that it would be premature to postulate such a process. It seems likely that monomer participates in the initiation of chains, but there is no unambiguous evidence to suggest how this process might occur. In view of these problems a detailed discussion of possible reactions is hardly relevant at the present stage, and this must await the results of future experimental work.
Theory of Branching Processes and Statistics of Rubber Elasticity
Authors: Dobson G. R. , Gordon M. 
Published: February 2011

Abstract
Recent efforts to reformulate statistical theories of polymeric systems in terms of the theory of branching (“cascade”) processes, are here extended to calculations of statistical parameters for the theory of rubber elasticity, viz., the number and mean length of various forms of active network chains. New simple results are given for random ƒ-functional polycondensation; it is shown that such systems are of interest in rubber elasticity studies in the region just after the gel point, where the concentration of active network chains varies rapidly with conversion, while the mean length of these chains diverges at the gel point. General exact formulas are derived for random crosslinking of arbitrary primary distributions, without assuming that the mean primary chain length is necessarily large; examples are worked out for uniform (homodisperse) chains, random, self-convoluted random, or Poisson primary distributions. Calculations are extended also to the cross-polymerization type of vulcanization reaction attributed to the cure of polybutadiene with peroxides. The results suggest reasons for differences in technical performance observed with such rubbers.
Elastomer Behavior IV. Loop Structure of Elastomer Networks
Authors: Case L. C. , Wargin R. V. 
Published: February 2011

Abstract
A new theoretical treatment strongly indicates that an elastomer network actually consists of a system of fused, closed, interpenetrating loops of polymer chains. This interpenetrating loop structure restricts the movement of the chains and thereby affects the stress-strain behavior of the elastomer. Methods have been developed to enable the calculation of the number of effective crosslinks caused by loop interpenetrations (virtual crosslinks). The uniaxial stress-strain behavior of an elastomer predicted using our methods can be fitted almost perfectly to published experimental data by proper selection of chain parameters. Previous theoretical treatments gave only a qualitative fit to the experimental data for the stress-strain behavior of elastomers and were not capable of predicting the correct shape of the experimental stress-strain curve. The present treatment gives a nearly perfect fit for both stress as a function of strain at constant crosslink density, and stress as a function of crosslink density at constant strain, and thus represents a vast improvement.
Carbon Black Reinforcement in Pre-Swollen Rubbers
Authors: Cotten G. R. 
Published: February 2011

Abstract
The mechanism of carbon black reinforcement was studied by examining stress-strain properties in SBR 1500 vulcanizates cured while swollen, then de-swollen. Carbon black-polymer attachments started contributing to the modulus of rubber at much higher elongations (ca. 300 per cent for a swelling ratio of 4.0) than in normally cured, unswollen specimens. The modulus in pre-swollen rubbers is considerably lower than in normal vulcanizates but it can be increased by heating the same specimens 30 minutes at 155° C in their de-swollen state. The observed increase in modulus of vulcanizates containing graphitized and regular carbon blacks after such a treatment was found to be related to carbon black “activity” and loading. Bound rubber does not seem to function as a distinct phase contributing to reinforcement, but it can be used as a measure of the number of attachments of carbon black and polymer. Additional information on the molecular mechanism of the phenomenon was obtained through radioactive tracer analysis. It was also found that regular vulcanizates can be softened by heating swollen samples at elevated temperatures (150-170° C). This softening was related to carbon black “activity” and was fully reversible: the original modulus could be recovered by additional heating of de-swollen vulcanizates for a further thirty minutes at 155° C. The above observations are discussed in terms of mobile adsorption of polymer chains on carbon black surface and the steric effect of fixing carbon black particles into an already extended polymer network.
Oxidative Stress Relaxation of Natural Rubber Vulcanizates at High Strains
Authors: Bell C. L. M. 
Published: February 2011

Abstract
The effect of high strain on the oxidative stress relaxation of several natural rubber vulcanizates has been investigated. In peroxide and CBS accelerated vulcanizates, the rate of stress relaxation increases with increasing strain, and this increase appears to be due to an increase in the rate of oxidation of the network. TMTD and MBT vulcanizates showed marked premature failure at high strains and no oxidative stress relaxation measurement could be made. The tensile strength of a TMTD vulcanizate was at least 20 per cent higher in vacuum than in oxygen, due, it is believed, to stress-induced oxidative degradation at the tip of surface flaws in the rubber.
Reaction of Ozone with p-Phenylene-Diamine and Related Compounds
Authors: Layer Robert W. 
Published: February 2011

Abstract
An improved method for measuring the relative rates of reaction of materials with ozone is given. This method is used to evaluate the reactivities of new antiozonants. The similar reactivities of isomeric N-alkyl-p-phenylenediamines indicate that antiozonants may in large measure be active as a result of the physical nature of the ozone and antiozonant (and possibly rubber) reaction product. Proton magnetic resonance spectroscopy was used to evaluate the types of products formed on the ozonation of p-phenylenediamines. These results are compared with previously reported infrared work. Evidence for a one electron oxidation of p-phenylenediamines with ozone is also presented. This evidence is not conclusive. A correlation of the HOMO energies of N-substituted p-phenylenediamines with the reactivities of p-phenylenediamines towards ozone is attempted. Although a rather broad correlation is noted, an exact correlation is not found. On the basis of these results, it is felt that the reaction between phenylenediamines and ozone may be free radical in nature. But the general type of substitution on the phenylenediamine alters the products that are formed and possibly changes the rate-determining step of the reaction.
Technological Characteristics of Polyisoprenes with Different 1,4-cis Contents
Authors: Bruzzone M. , Corradini G. , Amato F. 
Published: February 2011

Abstract
This work deals with the physical properties of polyisoprenes with different cis content. Small changes in the structural purity of these polymers affect strongly their crystallizability and, consequently, influence cured elastomer properties. In order to evaluate quantitatively the influence of cis content on elastomer properties it is clearly not sufficient to compare properties of the natural and synthetic polymers, obtained with different catalytic systems, relying on the same curing recipe. The difference in vulcanization kinetics, molecular weight distributions, dispersion of the ingredients in the elastomer, and other minor variables can in fact overshadow the influence of cis content on properties of the final product. In order to achieve a clear distinction between the effect of cis content and the influence of other variables, we decided to compare physical properties of vulcanized products over a large range of crosslink densities, obtained with suitable changes of the curing system, allowing for three variables: sulfur, accelerator, and curing time. The accelerator is a sulfenamide, suitable both for natural and synthetic polyisoprenes. When all the results obtained with different curing systems and times are plotted on a single diagram, in terms of physical property against crosslink density (or modulus) substantial differences between different polyisoprenes are noticed. In the low crosslink density range properties are probably influenced by network flaws related to the elastomer molecular weight distribution. Beyond a certain limit of crosslink densities the effect of molecular weight distribution decreases as the network flaws, mainly due to the ends of the primary chains, become less and less important. In this crosslink density range, properties are related mainly to structural purity, which influences the crystallizability of the network chains and perhaps also the nature of the inter or intramolecular bonds formed by curing.
Radiation Induced Block or Graft Co-Polymers of Methyl Methacrylate with Isobutylene and Ethylene Propylene Rubbers
Authors: Pellon Joseph , Valan Kent J. 
Published: February 2011

Abstract
Attempts to prepare block or graft copolymers of isobutylene rubbers by radiation in the presence of methyl methacrylate gave low yields of copolymer with only 20 per cent of the rubber entering into the copolymer. The remainder of the rubber is degraded during the process. A single experiment describes the graft copolymerization of methyl methacrylate with ethylene propylene rubber in which 45 per cent of the rubber is copolymerized.