bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extraction of Low Molecular Weight Materials from Gel Spherules, Using the System: Benzoic Acid/Cyclohexane/Crosslinked Polyisoprene
Authors: Hummel K. , Fuge Ch 
Published: February 2011

Abstract
Solid spherules of polyisoprene with different crosslink densities, radius 3 mm, were produced in closed, two-part steel molds, at 150° C, from purified natural rubber containing cumyl peroxide, (0.3 to 40 mmol/100 g of polymer). The spherules were swelled in a solution of benzoic acid (1.3 weight per cent) in cyclohexane at 25° C is equilibrium which was reached after about two days. Equlibrium swelling Q is defined as the weight ratio, swelling agent/polymer, for the polymer swelled to equilibrium; 1/Q increases with crosslinking and serves therefore as a measure of crosslinking. The swelled spherules were extracted with cyclohexane or water, at 25° C, in a flow-through, agitating vessel (with vigorous stirring of the liquid) in such a way that the concentration of benzoic acid in the extract was always negligibly low compared to the average concentration in the gel-phase. Quantity of benzoic acid in the gel spherule, M0, was determined before extraction, and also the residual quantity, Mt, as a function of extraction time.
The Migration of Extender Oil in Natural and Synthetic Rubber, III. Relative Contributions of Principal Structures in Aromatic Fractions to Diffusion
Authors: Lewis James E. , Deviney Marvin L. , Corman Blaine G. 
Published: February 2011

Abstract
Migration in rubber is a general phenomena of practical importance. A basic program using radiotracers was undertaken to help understand this migration and establish a rating system to allow the compounder to predict the behavior of a given oil from its molecular structure and that of the elastomer. The aromatic portion of a 14C labelled aromatic oil was separated into fractions of relatively narrow molecular-type distribution by silica gel solid—liquid chromatography. Static migration studies were made in natural rubber, SBR, cis-polybutadiene and emulsion polybutadiene rubber over the temperature range 50–125° C. Computer-derived diffusion coefficients were calculated, normalized by a least squares technique and used to calculate migration activation energies and to correlate the diffusivity of the oil fractions with degree of aromatic condensation. The data obtained indicate that moderate variations in the molecular composition of the aromatic components of an extender oil would have only a minor effect on the migration characteristics of the total oil.
Hydrogen Evolution from Natural Rubber During Tensile Tests
Authors: Andrews E. H. , Reed P. E. 
Published: February 2011

Abstract
Tensile tests performed on oriented natural rubber (NR) at temperatures below −120° C have produced an interesting phenomenon of foaming caused by the evolution of hydrogen. The unfilled natural rubber was oriented by extending it by 100% at room temperature and then cooling it to the test temperature of −120° C. At this temperature the amorphous material is in the glassy state and no crystalline material is present. It was expected that under these test conditions the rubber would fail in a brittle manner but at a slow extension rate of 0.2 cm/min a yield point was reached and the specimens then underwent extensions of up to 200% in excess of the initial 100%. After removal from the test chamber the specimens had a whitish appearance and as they warmed up considerable swelling took place (Figure 1) and large bubbles formed on the surface. Figure 2 shows a freshly cut surface through a foamed region. These surface bubbles often burst noisily. After several hours all signs of foaming had disappeared except for the craters left from burst bubbles and the material was again rubbery. The gas emitted from the foamed material was collected over water and, on analysis by GLC and mass spectrography, was found to be pure hydrogen. The evolution of hydrogen from NR has been previously reported during irradiation where according to one explanation it could be due to main chain breakage followed by the free radical joining another chain with the subsequent evolution of hydrogen. It therefore appears that at low temperatures and low strain rates, main chain rupture occurs during yield, the broken chain ends then attaching themselves to other chains. Such a process should increase the number of crosslinks in the material and hence reduce the intercrosslink molecular weight (Mc). Swelling tests on the material before and after foaming show that Mc is reduced from 6650 to 4900, basing the calculation on the Flory—Rehner equilibrium swelling equation.
Mechanical History Effects in the Crystallization of cis-1,4-Polybutadiene
Authors: Mitchell J. C. 
Published: February 2011

Abstract
Dilatometric studies have revealed alterations in the crystallization kinetics of cis-l,4-polybutadiene subjected to the shearing action of a laboratory mill. Reduction in the Avrami exponent by more than one unit suggests that, in addition to a change from pseudo-homogeneous to instantaneous nucleation, a change in the growth mechanism of the new phase is involved. These changes are presumed to be brought about either by sub-optical microscopic ordering of the amorphous polymer (e.g., the ‘quasi-indestructible’ clusters proposed by Rabesiaka and Kovacs) or by shear effects on. impurity constituents, with either effect leading to row orientation.
Recrystallization and Melting of Partially Melted Stark Rubber
Authors: Roberts Donald E. 
Published: February 2011

Abstract
Two specimens from a piece of stark rubber which had a melting temperature originally at 41° C were partially melted at 38° C and allowed to stand for 11 years, one at about 25° C, the other at 38° C. The first showed a continuous slow decrease in specific volume, while the second increased slowly in volume for 5 months and remained constant for about 5 months more before showing the continuous slow decrease. The melting temperature of the first increased to 45° C and the melting range was broadened. The melting temperature of the second became 52° C and the range was narrowed. Perfecting or enlarging of crystals and the effect of higher recrystallization temperatures have influenced the melting temperatures. The effect of heating rate is discussed in connection with slow increases in volume, attributed to relaxation of oriented regions, during melting.
Poisson's Ratio for Stretched Vulcanized Natural Rubber
Authors: Sekiguchi H. , Kakiuchi M. , Morimoto T. , Fujimoto K. , Yoshimura N. 
Published: February 2011

Abstract
Changes in the Poisson's ratio of natural vulcanized rubber due to elongation were investigated experimentally. The following results were obtained: If infinitesimal deformation at any instant during elongation is considered, it appears to be correct to take the Poisson's ratio at such instants as 0.5. If the apparent Poisson ratio when a certain standard mark is taken and a large deformation imparted is considered, and the elongation ratio is made α, the Poisson's ratio decreases from 0.5 in accordance with the equation log10 (1/m)=0.0204α2−0.261α−0.0628. This equation is valid for subsequent elongations, no matter what elongation situation is taken for the standard marks. These two results do not vary with the carbon black content or on repeated stretching.
Behavior of Unfilled and Filled Rubbers in Shear in the Glass Transition Region
Authors: Schwarzl F. R. , Bree H. W. , Nederveen C. J. , Schwippert G. A. , Struik L. C. E. , Van der Wal C. W. 
Published: February 2011

Abstract
Rubbers filled with high amounts of a hard inorganic filler still show typical mechanical properties of a high polymer, viz., a glass transition region, a glassy state and a rubbery state. Effects of filler characteristics on the glass transition are discussed, chiefly on the basis of the course of shear modulus at constant frequency as a function of temperature. Effect of volume content of filler on the glass transition of composite materials consists chiefly in a change of the levels of shear modulus in the glassy and in the rubbery state. This change may be described by a simple macroscopic model due to van der Poel. Predictions by this theory could be confirmed for rubbers filled with single filler fractions in the filler size range 30 to 500 µm, and in the range of filler content 0 to 50 vol%. At smaller particle sizes, an effect of filler size was observed, which points to increase in the transition temperature and to increase in the level of modulus in the rubbery state with decreasing filler size. Preparation of composite materials with high filler contents (&gt;55 vol%) is only possible by using a filler with a bimodal size distribution. In this case, moduli depend on filler content and mixing ratio of coarse to fine filler fraction; the van der Poel theory then gives predictions which are too high in comparison with experimental results.
Influence of Carbon Black Structure on Vulcanizate Properties
Authors: Price C. R. , Aboytes Peter 
Published: February 2011

Abstract
Samples of carbon black representing regular and high structure levels of HAF and ISAF were subjected to ball milling under an inert atmosphere for varying periods of time. The structure level varied inversely with duration of ball milling. Tests of the various blacks in SBR revealed that the persistent or reinforcing structure was changed by ball milling and not just the transient structure. It was also shown that laboratory abrasion resistance was greatly reduced by reducing the structure below a level of DBP absorption of 100–110 cm3/100 gms. Above this level, structure did not seem to contribute significantly to abrasion resistance.
The Measurement of Cord Tensions in Tires
Authors: Patterson Ralph G. 
Published: February 2011

Abstract
Tensions were measured in the reinforcing cords of tires during curing, post-inflation, and in service, using a miniature transducer employing resistance strain gauges. Cord tension varied throughout the cure cycle and was influenced by temperature, ply fabric width, cord modulus, and shrinkage. The cord tension reached a maximum (i.e., 2.2 lb) immediately after mold closing when the tire was forced out to mold dimensions. The tension was proportional to the fiber modulus and inversely proportional to the width of ply fabric. About two minutes after mold closing, the tension decreased sharply because the rubber became soft. The cord position shifted in the rubber and the tension was removed. Thereafter, thermal shrinkage of the fiber determined the cord tension as the tire temperature increased and the rubber cured around the cord. During post-inflation, tension was proportional to inflation pressure and reached 5.0 lb at 35 psi. Under these conditions, the cord stretched and tire size was related to cord extensibility. Tension in the cured tire increased in proportion to inflation pressure and was at a maximum at the tread center (3.0 lb at 24 psi), decreasing toward the bead to 2.3 psi. These findings were in agreement with calculations based on membrane theory. In straight running, cord tension in ply one opposite the center of the tread followed an essentially sawtooth pattern, decreasing below the inflation tension (from 3.0 lb to 1.4 lb) and returning to the inflation tension as the point of measurement moved into and out of the deflected region at the road surface. Increasing or decreasing inflation pressure shifted the sawtooth profile up or down without changing its basic shape. At constant pressure (i.e., 22 psi), increasing load from 700 to 1200 pounds increased the tension decrement from 1.1 to 1.5 lb. The principal effect of speed was to increase the overall tension because of higher operating pressure without significantly changing the sawtooth pattern. A condition of severe overloading, underinflation, or a combination of the two caused the cord in the sidewall to go into compression. This is believed to contribute to fatigue damage, based on previous work.
Evidence for Chemical Interaction in Carbon and Polymer Associations. Extension of Original Work on Effect of Carbon Black Structure
Authors: Gessler A. M. 
Published: February 2011

Abstract
Selected proposals regarding the mechanism of carbon and polymer interaction were reviewed from the literature. With this material as background, the bound rubber capacity of low and high structure HAF blacks was studied over a broad concentration range in four previously unstudied polymers: ethylene-propylene copolymer, chlorinated butyl, cis-1,4-polybutadiene, and natural rubber. Experimental evidence from the resulting work was combined with that from a similar previous study involving five polymers: polyisobutylene, butyl, two ethylene-propylene terpolymers differing in free radical activity, and SBR. With low structure black, the extent of bound rubber formation varies with the activity of the polymer functionality, in accordance with expectation. Previously proposed mechanisms for the bonding of rubber and black are used to resolve the differences which are shown. With high structure black, the primary carbon-to-polymer bonding effects referred to above are overshadowed by the formation, in situ, of a facile, new free radical source which is proposed to result from the mechanical breakage of aggregated carbon black structure during the milling of rubber and black. This imposed free radical activity is shown to have a profound effect on the subsequent behavior of the polymer. The inclusion of sulfur (2.0 php) in bound rubber systems leads to some extremely interesting results. Except for natural rubber, polymer is not crosslinked by the action of sulfur alone, even when the systems are heated as in vulcanization. The high bound rubber levels which are formed when sulfur and black are both present, especially with butyl, are proposed to result first from a reaction of sulfur with the black, and second, from reaction of this sulfur-modified black with the polymer. The close relationship between vulcanization and reinforcement is thus attested.
Electrical Properties of Stretched Carbon Black Loaded Vulcanizates
Authors: Voet Andries , Sircar Anil K. , Mullens Troy J. 
Published: February 2011

Abstract
To study the function of the carbon network, electrical conductivities and dielectric constants were measured on carbon black filled vulcanizates through the full range of elongation. Data were obtained for a variety of elastomers and carbon blacks, at different loading levels and covering the commercial particle size and structure ranges. The influence of the temperature and strain rate was investigated. In most of the reinforcing blacks there is a pronounced fall in conductivity and a minor decrease in dielectric constant in the first area of elongation, corresponding to the elimination of the transient structure. This is followed by an area of steady increase, caused by alignment of persistent carbon chains. At still higher elongations a sharp decrease occurs, due to destruction of carbon-elastomer bonds. The first two effects are very pronounced in high structure blacks but negligible in very low structure reinforcing blacks. The third effect leads to hysteresis and irreversible changes in the vulcanizates. Graphitized carbon black, with little or no bonding to the elastomer, does not show the third effect. Particle-elastomer adhesion data, obtained by an electron micrographic replica technique, independently confirmed the results. Anisotropy in electrical conductivity was observed. The major significance of the carbon filler in stress softening is discussed.
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
Authors: Lewis James E. , Deviney Marvin L. , Whittington Lawrence E. 
Published: February 2011

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.
Determination of Carbon-Bound Lithium in Polymer Cements
Authors: Turner R. R. , Gaeta L. J. , Altenau A. G. , Koch R. W. 
Published: February 2011

Abstract
A simple and direct titration procedure for the determination of carbon-bound lithium in lithium catalyzed polymer cements has been developed. It utilizes the specific reaction of allyl bromide with carbon-bound lithium. Since this procedure was used for a solution of polymer in hydrocarbon, reagents were selected to avoid phase separation. This procedure has been used over a catalyst range of 1.5 to 0.5 millimoles per hundred weight polymer. The resulting polymers had molecular weights from fifty thousand to five hundred thousand.
Ozone Crack Initiation: Statistical and Deterministic Interpretations of Action of p-Phenylenediamines and EPDM as Antiozonants
Authors: Ambelang J. C. , Wilson F. H. , Porter L. E. , Turk D. L. 
Published: February 2011

Abstract
The time to first visible crack of ozone sensitive vulcanizates appeared to be short and replicable 3–5 h at 25 pphm ozone, 2 h at 50 pphm. For antiozonant protected OE-SBR below the critical strain, the time to first visible crack was found to be a stochastic value with a normal or log normal distribution.
Carbon Black Morphology: I. Particle Microstructure. II. Automated EM Analysis of Aggregate Size and Shape
Authors: Hess W. M. , Ban L. L. , McDonald G. C. 
Published: February 2011

Abstract
Carbon black particle and aggregate microstructure were studied in detail by means of high resolution electron microscopy. Improved instrumental and environmental conditions have enabled more detailed studies on the size, orientation, and spacing of graphite layers in carbon black particles than heretofore possible. The layers form continuous networks about particle growth centers and between adjoining particles and show a paracrystalline orientation rather than individual crystallites. Based on this type of orientation carbon black primary aggregates are now defined as single graphite paracrystals exhibiting either a fibrous (furnace and channel blacks) or spheroidal (thermal blacks) shape.
All-cis Polypentenamer: A Potential New Elastomer for Low-Temperature Applications
Authors: Dall'Asta G. , Scaglione P. 
Published: February 2011

Abstract
On the basis of the above results it can be concluded that the low-temperature characteristics of all-cis polypentenamer are better than those of any other hydrocarbon elastomer and that they can even be competitive with those of much more expensive extremely low-temperature elastomers, like silicone rubber.
Dependence of the Crosslinking Efficiency on the Reaction Conditions in the Peroxide Crosslinking of Unsaturated Polyolefins
Authors: Aahikari Nobuyuki , Kawashima Izumi , Kawashima Takehisa 
Published: February 2011

Abstract
The crosslinking reactions of several unsaturated polyolefins with organic peroxides were carried out in an attempt to establish the dependence of the crosslinking efficiency on the reaction conditions, especially the reaction temperature and the peroxide concentration. Usually, the efficiency gradually increased up to a certain temperature and then decreased abruptly. This efficiency decrease can be considered to be due to (1) a decrease in the hydrogen abstraction, which is one reaction producing crosslinks, and (2) an increase in the termination rate in a chain reaction arising from opening up the double bond, which is another reaction producing crosslinks. Except for cases in which an extremely high temperature was employed or when a very high concentration of peroxide was used, the efficiency decrease by scission at higher temperatures seems to be comparatively small.
Viscoelastic and Ultimate Tensile Properties of Styrene-Butadiene-Styrene Block Copolymers
Authors: Smith T. L. , Dickie R. A. 
Published: February 2011

Abstract
A study was made of the stress—strain and ultimate properties in simple tension of an elastomeric styrene—butadiene—styrene block copolymer (Kraton 101) and also of a similar material (Thermolastic 226) that contains about 35% plasticizer as well as inorganic pigments. Stress—strain data were obtained at crosshead speeds from 0.02 to 20 in./min at temperatures from − 40 to 60° C. The relaxation rate, derived from the data at constant extension rates, was about 8% per decade of time for both materials at temperatures from − 40 to about 40° C and at extensions from about 20% up to 400%. Above − 30° C, the shift factor log aT was found to vary linearly with temperature. These findings indicate that the time and temperature dependence of the mechanical properties results primarily from the plastic (or viscoelastic) characteristics of the styrene domains. The tensile strength for Kraton 101 below 40° C is somewhat greater than 4000 psi, sensibly independent of extension rate and temperature. For the highly plasticized Thermolastic 226, the tensile strength at an extension rate of 1.0 min−1 increases from 2200 psi at 0° C to 3600 psi at − 40° C. Above 40° C for Kraton 101 and above 0° C for Thermolastic 226, the tensile strengths are dependent on extension rate and temperature owing to the increased ductility of the styrene domains. The high strength of these materials results from the uniformly dispersed styrene domains of colloidal dimensions. To obtain a crack of sufficient size to satisfy an energetic criterion for self-sustained high-speed propagation, domains must be disrupted. The plastic characteristics of the domains have a controlling effect on crack growth and thus on the ultimate properties of the materials. The strength and extensibility of other elastomers are considered in relation to those of the block copolymers.
The Effects of Mechanical Degradation on Rheological Properties of Elastomers
Authors: Folt V. L. 
Published: February 2011

Abstract
Several anomalies are observed in the flow of the melts of many elastomers which are not commonly observed with melts of plastics. A stress-oscillation at high rates of shear and a tendency to reach a constant level of stress at lower rates of shear are two of the more commonly encountered anomalies. Both anomalies occasionally occur in the flow of a single melt. The role of molecular weight, molecular weight distribution and branching in producing anomalous flow is demonstrated. The presence of supermolecular flow units is invoked to explain certain anomalies and supporting evidence is presented. The data strongly suggest changes in the rheological flow units take place as the conditions of shear are changed. The flow properties of many elastomers are complicated by the severe mechanical degradation taking place under these conditions of shear. Anomalous flow patterns can be either produced or removed by mechanical degradation depending upon the specific elastomer system. The extent of degradation appears to be dependent upon the flow unit governing the flow process and independent of the shearing stress or work input per unit volume of polymer sheared. The complexity and distribution of entanglements play a major role in the flow processes as well as in the mechanical degradation process of certain elastomers.