bluuebunny/crossref_metadata_2025_split huggingface dataset:
Important Mechanical and Chemical Factors in the Failure Behavior of Polybutadiene Rubber Undergoing Oxidative Aging at Ambient Temperature
Authors: Kim C. S. 
Published: February 2011

Abstract
Zhurkov's molecular kinetic concept of failure for hard solid materials was extended for application to rubber systems which undergo oxidative degradation during long-term atmospheric exposure. In an effort to analyze the chemical and mechanical effects separately, the dependency of the life-time of the uniaxially stressed rubber was expressed in terms of (1) chemical effects involving the primary chemical bonds in the effective chains, and (2) mechanical effects involving the network structure of the rubber.
The Contribution of Deformation Losses to Rubber Friction
Authors: Hegmon R. R. 
Published: February 2011

Abstract
Bulk friction of rubber is defined as the friction due to deformation losses. Analytical and experimental investigation of bulk friction showed excellent agreement. The coefficient of bulk friction depends on the geometry of the rough surface and increases linearly with the mean pressure. Friction depends on two dynamic rubber properties, it decreases with increasing dynamic modulus and increases with increasing damping factor.
Sulfur Crosslinks in Polybutadiene Vulcanizates
Authors: Gregg Earl C. 
Published: February 2011

Abstract
For the first time the crosslink terminus structure of monosulfide crosslinks and the amount of that structure in an elastomer vulcanizate has been determined directly from a sample of the vulcanizate. By measuring the rate of swelling of vulcanizates, immersed in either methyl iodide or methyl bromide, the rate of crosslink cleavage was measured. Comparison of this cleavage rate with the cleavage rate of model monosulfide compounds permits a measure of the terminus structure of the monosulfide crosslinks. The fraction of each monosulfide structure was determined from the cleavage rate equation for the vulcanizate. The monosulfide crosslink terminus structure in a particular polybutadiene vulcanizate was found to be saturated, having secondary carbon atoms on both sides of the sulfur atom, i.e., it was a saturated, tetrafunctional crosslink equal to 38% of the total crosslinks.
Nuclear Magnetic Resonance Study of the Interaction of SBR with Carbon Black
Authors: Waldrop M. A. , Kraus G. 
Published: February 2011

Abstract
The nuclear magnetic resonance relaxation characteristics of an amorphous styrene—butadiene copolymer (SBR-1500) containing HAF and ISAF carbon black and an HAF carbon black containing SBR-1500 adsorbed on it from solution have been investigated at 30 Mc/sec over a temperature range of −100° to 100° C. The spin-lattice relaxation time (T1) passes through a single, broad minimum at about 30° C. The precise location of this minimum which is ascribed to the onset of segmental motion in the copolymer is not strongly dependent on the presence of carbon black. The nuclear magnetic resonance results reported suggest that the spectrum of correlation times of the elastomer strongly associated with the carbon black particles, i.e., the “bound rubber” is not significantly different from that of the bulk elastomer containing no carbon black—at least for the frequencies sampled by the NMR technique used. The results thus fail to confirm recent proposals in the literature suggesting that filler particles in elastomers are covered with a layer of polymer in which segmental motion is severely restricted and which constitutes a significant, if not the major portion of the rubber.
Heterogeneity and Crosslinking of Elastomer Blends. Investigations of Chlorobutyl with Highly Unsaturated Elastomers
Authors: Rehner John , Wei Peter E. 
Published: February 2011

Abstract
Literature on the fundamental physios and chemistry of elastomers blends is limited, even though blends are employed commercially. Past research on individual elastomers is inadequate for a good understanding of blends. Properties of elastomers blends, unlike those of plastic blends, depend on vulcanization chemistry. The general problem is therefore one of understanding the nature and properties of elastomer blends in which complex chemical reactions have been superimposed on a complex physical state. The present paper is a preliminary examination of both of these aspects.
Elastically Effective Strand Density in Polymer Networks
Authors: Langley N. R. 
Published: February 2011

Abstract
A new expression is derived which relates the density of elastically effective strands in a polymer network to the densities of random cross-links, main-chain scissions, and entanglements and to the molecular weight distribution of the initial linear polymer. Methods are recommended for characterizing the cross-link and scission densities from measurable sol fractions and for determining the entanglement density empirically. The strand density can be evaluated quite easily for the random and uniform initial molecular weight distributions. The new expression differs appreciably from that of Mullins and Bueche, owing principally to a new criterion for effectively trapping network entanglements. The statistical approach used to derive the strand density is also used in a new derivation of an existing implicit expression for the gel fraction.
Kinetics of Accelerated Vulcanization—III N-Cyclohexyl-Benzothiazole-2-Sulfenamide Accelerated Sulfur Vulcanization of Rubbers
Authors: Bhatnagar S. K. , Banerjee S. 
Published: February 2011

Abstract
Sulfenamide type of accelerators are well known for their outstanding processing safety combined with ultra-strong accelerating activity resulting in superior quality vulcanizates. Sulfenamides derived from different amines afford varying degrees of scorch delay and accelerating activity. Since there is no unanimity on the chemistry involved in this type of accelerated vulcanization, a preliminary study has been carried out to gain some insight into the mechanistic scheme. The present paper contains reports on the effects of varying concentrations of N-cyclohexyl-benzothiazole-2-sulfenamide (CBS) on the rate of free sulfur decrease and cross-link formation as well as zinc sulfide formation—whenever it occurs—both in the absence and presence of zinc oxide and of zinc oxide and stearic acid. The influence of temperature has also been investigated.
Thermodynamics of Mixing of n-Alkanes with Polyisobutylene
Authors: Flory P. J. , Ellenson J. L. , Eichinger B. E. 
Published: February 2011

Abstract
The volume changes on mixing polyisobutylene (PIB) with n-pentane, n-hexane, n-heptane, n-octane, n-decane, and n-hexadecane have been determined by direct measurements at 45°, and for n-heptane at 0 and 50° as well. They are negative in every case; the magnitude of the excess volume decreases with chain length, and increases with temperature. These results on volume changes, which are beyond the scope of conventional theories of polymer solutions, are rationally taken into account by the recent statistical mechanical theory of solutions which relates properties of the mixture to characteristics of the pure liquids manifested in their equation-of-state parameters. The negative enthalpies of mixing found by Delmas, Patterson, and Somcynsky for all of these systems with the exception of PIB-n-hexadecane are similarly shown to arise from negative equation-of-state contributions to the enthalpy which reflect differences between the liquid characteristics of n-alkane and PIB. The energy contributed by interchange of neighbor species in contact is shown to be small but positive, as should be expected for the nonpolar molecules involved. It diminishes with chain length of the alkane, becoming little greater than zero in the limit of an infinite alkane chain (polymethylene). Osmotic pressures of concentrated solutions (∼ 15–50%) of PIB in n-octane at 25° yield values of the residual chemical potential, expressed in terms of the conventional parameter χ, which are well reproduced by the theory without arbitrary parameters. The partial molar enthalpy and entropy of dilution are dominated by equation-of-state contributions rendering both of them negative, despite the large positive combinatory entropy. The appearance of critical miscibility at higher temperatures is thus predicted by the theory without resort to special explanations.
Determination of the Equation of State of Polyisobutylene
Authors: Eichinger B. E. , Flory P. J. 
Published: February 2011

Abstract
The density, thermal expansion coefficient, and thermal pressure coefficient for polyisobutylene of mol wt 40,000 have been accurately determined from 0 to 150°. Results are compared with the reduced equation of state employed in the theory of solutions. The characteristic parameters v*, T*, and p* required for the treatment of polyisobutylene solutions are obtained from the experimental results.
Cuts and Cut Growth in Tires
Authors: Brenner F. C. , Barton F. W. 
Published: February 2011

Abstract
Forty tires were subjected to severe road use on a course (approximately 3500 miles) that included Belgian block, over highways at turnpike speeds while overloaded. The course was repeated until the tires were worn smooth. At the end of each course, the number of new cuts and the length of all cuts in grooves was determined. Ten miles of Caliche (sharp stones) road was included between the first and second measuring period. The tires experienced a total of 169 cuts. Forty seven of these grew, 34 of which grew less than 0.11 inch. No cut grew continuously throughout the test. The cuts grew but not enough to cause tire failure except in one case where the cut exposed the fabric.
Intercalated Montmorillonites as Fillers for Acrylonitrile-Butadiene Rubber
Authors: Zaborski Marian , Kunert Anna , Pietrasik Joanna , Szynkowska Malgorzata Iwona , Lesniewska Ewa 
Published: February 2011

Abstract
Modified montmorillonite was used as filler for NBR. The effect of the montmorillonite structure and its concentration was studied. The composites were prepared with the use of a laboratory two-roll mill. Unmodified montmorillonite (MM_Na) agglomerated in NBR rubber resulting only in small enhancement of mechanical properties. The most effective exfoliation of the montmorillonite was observed for the modifier with two long chains (dihydrotallowdimethylammonium chloride (2M2HT)) and at its higher concentration (C1). The modified filler did not agglomerate in NBR. The montmorillonite (MM_2M2HT(C1)) formed a secondary filler network. This very well dispersed network demonstrated the strong reinforcement. Increasing the content of MM_2M2HT(C1) to 20 parts by wt. improved significantly the tensile strength of NBR vulcanizates (tensile strength &gt; 25 MPa). Montmorillonite intercalated with hydrotallowdimethylbenzylammonium chloride (MM_2MBHT) did not improve the properties of the studied materials.
Oil Distribution in iPP/EPDM Thermoplastic Vulcanizates
Authors: Abraham Tonson , Barber Norman G. , Mallamaci Michael P. 
Published: February 2011

Abstract
Scanning Probe Microscopy (SPM) was used to determine the volume fraction of oil-swollen particulate rubber and oil-swollen plastic in thermoplastic vulcanizates (TPVs) produced from iPP and EPDM rubber. Sample preparation and SPM imaging conditions allowed the ratio of the rubber and plastic area imaged for a TPV sample to be equated to the phase volume ratio. The hydrosilylation cured TPVs contained no filler or inorganic components (other than about 1 ppm of platinum catalyst, based on dry rubber) that would decrease the accuracy of the SPM analysis. The accuracy of the SPM method used for TPV phase volume determination was established by analysis of an oil-free TPV of known composition. The densities of the individual TPV components (rubber, oil, crystalline and amorphous plastic phase), which were assumed to be additive in the composite, were used to calculate the oil distribution between the TPV rubber and plastic phase, since the volumes of the individual components (the extent of plastic crystallinity was measured by differential scanning calorimetry) were known. Thus, the amount of oil in the oil-swollen TPV rubber and plastic phase could be quantified. This information, coupled with the Tg of the oil-swollen amorphous plastic phase, indicated that a substantial amount of oil was present as a separate oil phase that is surrounded by the oil-swollen amorphous plastic phase. To date, it has been assumed that the oil in a TPV partitions between the rubber and amorphous plastic phase, with the plastic crystallites being oil free. This work is the first demonstration of the presence of a separate oil phase in TPVs, and the first accurate determination of the oil content in the oil-swollen rubber, miscible oil in the oil-swollen amorphous plastic, and the free oil in TPVs.
Mechanical and Swelling Behavior of Double Networked Natural Rubber Cured Using a New Binary Accelerator System
Authors: Marykutty C. V. , Mathew G. , Thomas Sabu 
Published: February 2011

Abstract
The concept of double networks, which impart chain orientation to elastomers, is a rather new idea. Double networks were induced in natural rubber vulcanizates cured with different accelerator systems. Double networked natural rubber with different extensions cured with N-cyclohexyl benzothiazyl sulphenamide (CBS) and 1-phenyl 5-ortho -tolyl 2,4 dithiobiuret was studied and the effect of extension on the mechanical properties and swelling was analyzed. The extent of chain orientation was analyzed through anisotropic swelling studies. The modulus, tensile strength and tear strength showed an increase with increased residual extension ratio. The effect was more predominant in the longitudinal direction than in the transverse direction. The ultimate tensile elongation showed a slight deterioration. It was revealed that the formation of double networks with higher residual extension ratios restricted the entry of the solvent. Based on the studies it was concluded that residual extension has a profound effect in determining the final properties of vulcanizates.
T-Peel Tearing of a Model Black-Filled Natural Rubber Tread Ply Vulcanizate
Authors: Adamu B. , Hamed G. R. 
Published: February 2011

Abstract
T-peel tearing of a model black-filled natural rubber tread ply vulcanizate has been carried out. Tearing alternates between slow (“stick”) and fast growth stages (“slip”). “Stick” fracture involves sideways cracking into the loading direction. This blunts the peel front, slows forward tearing, and results in rough fracture surfaces. “Slip” fracture is the sudden forward growth of a crack, leaving relatively smooth fracture surfaces. “Stick-slip” fracture is characteristic of highly reinforced rubbers; it is also seen in edge-cut tensile specimens and trouser tear specimens of black-filled NR.
Reinforcement of Polyisobutylene with Anisodiametric Filler Particles of Poly(Ethylene Terephthalate)
Authors: Kargin V. A. , Sogolova T. I. , Metelskaya T. K. 
Published: February 2011

Abstract
The addition of particles of anisodiametric shape to a polymer, in the absence of chemical reaction, has a considerable influence on the mechanical properties of the polymer even with comparatively low concentration of the filler. It may be safely stated that the increase in strength, in 50% modulus, and in the flow temperature of filled systems is connected with the shape and dimensions of the particles which have been added. The conditions under which the experiment was carried out made it possible to observe the influence of the shape of the particles of the filler upon the physical and mechanical properties of the polymer in the pure form. It is suggested that the reduction in the temperature of flow which was observed with the addition of comparatively low concentrations of the filler with lengths not exceeding 100 µ, is due to the action of such fillers upon the secondary structures in the amorphous polymer.
Carbon Black Structure in Rubber
Authors: Payne A. R. , Watson W. F. 
Published: February 2011

Abstract
Some of the properties of carbon blacks in rubber are ascribed to its “structure”. This paper presents results on the sinusoidal dynamic straining of rubber/carbon black vulcanizates over an amplitude range including strains less than 0.1% and suggests that an elucidation of structure effects and the nature of the structure underlying them is forthcoming from these results. The dynamic properties are profoundly modified by special processing. Heat treatment of stocks containing structural carbon blacks and particularly the use of N-methyl-N,4-dinitrosoaniline can greatly reduce structure effects. They are absent with attrited blacks. Similar results have been obtained with silica fillers, for which certain metal soaps virtually eliminate structure effects. Structure effects are shown to be not essentially related to the rubber network, including the type of rubber, but to be due to a physical, three-dimensional structure of the filler itself within the rubber; the rubber acts merely as a dispersing medium and a matrix to allow the filler structure to re-form after breakdown. These changes of the filler structure are often the major cause of hysteresis at low extensions. Mixtures of carbon black and organic liquids demonstrate the existence and properties of the physical carbon black structure in absence of rubber. The properties of the rubber have the structural effects of the filler superimposed upon them.
Mechanism of Antiozonant Action. I. Consumption of p-Phenylenediamines in Rubber Vulcanizates during Ozonization
Authors: Lorenz Otto , Parks Carl R. 
Published: February 2011

Abstract
The consumption of N,N′-bis(1-methylheptyl)- and N-isopropyl-N′-phenyl-p- phenylenediamine in cis-polybutadiene vulcanizates was measured as a function of the ozonization time and the initial diamine concentration. The results are consistent with a rapid reaction of the antiozonants with ozone and the formation of a protective layer on the surface of the rubber. Film formation was confirmed by microscopic studies. Besides direct reaction with ozone and film formation, chemical reactions between the p-phenylenediamines and ozonized rubber took place since a certain amount of the consumed diamine (up to 45 %) became attached to the rubber network.
Tensile Strength of Amorphous Gum Rubbers
Authors: Bueche F. , Dudek T. J. 
Published: February 2011

Abstract
A new molecular theory of tensile strength has been formulated for amorphous gum vulcanizates at temperatures well above the glass temperature and found to be in agreement with recent experimental data. It is shown that the stress on the rubber at break will consist of two parts, the normal kinetic theory stress on the network and the highly rate dependent stress held by the fully extended chains. The fraction of the chains in the fully extended state at the instant of break is greater for a lightly crosslinked rubber than for a highly vulcanized rubber under nonequilibrium test conditions. The theory allows the molecular weight of the freely orienting unit to be calculated. Reasonable values are obtained for EPR and SBR which lend support to the validity of the ideas involved. The kinetic-theory stress contributes the major portion of the stress at break in highly crosslinked amorphous gum rubbers. However, the stress at break for low degrees of crosslinking is largely the result of stresses in the most highly elongated chains.
Mechanism of Antiozonant Action. II. Effect of Antiozonants on the Ozonization of 2,6-Dimethyl-2,6-Octadiene and 2-Butene
Authors: Lorenz Otto , Parks Carl R. 
Published: February 2011

Abstract
The ozonolysis of 2,6-dimethyl-2,6-octadiene and 2-butene as model compounds for polyisoprene and polybutadiene was investigated using gas chromatography to follow the reaction. Ozonolysis led to mixtures containing mainly the corresponding carbonyl compounds and peroxy compounds, such as ozonides and polymeric peroxides. Ozonization of the model compounds in the presence of antiozonants or addition of antiozonants to the ozonized model compounds indicated that antiozonants react at least in three different ways: (a) All effective antiozonants reacted rapidy with ozone. (b) All antiozonants reacted readily with ozonides and slowly with polymeric peroxides, whereby the corresponding carbonyl compounds were formed. (c) Difunctional secondary amines, such as p-phenylenediamines, reacted readily with the formed aldehydes leading to polymeric compounds. In ozonized polydiene vulcanizates, a relinking of severed chain ends is achieved by this reaction, whereby the diamine becomes attached to the rubber network. Relatively basic amines effect aldol condensation of aldehydes.
Vulcanization of Rubber by Means of Resins
Authors: Thelamon Claude 
Published: February 2011

Abstract
Vulcanization has been the subject of much careful research since its discovery by Goodyear in 1840. Originally “vulcanization” meant a treatment of rubber with sulfur and heat, but now the word has a much broader connotation, since it has been discovered that numerous substances can produce the same effect as sulfur. Vulcanization is the process by which rubber passes from the predominantly plastic state to a predominantly elastic state by means of an irreversible transformation. This phenomenon is due to the formation of intermolecular bridges, leading to a more or less dense steric structure. Materials capable of vulcanizing rubber can be classified in three large categories: 1. Compounds which liberate sulfur during vulcanization, e.g., sulfur chloride and tetramethylthiuram disulfide. It is thought that nascent sulfur is particularly active, giving rise to the formation of crosslinks. 2. Compounds inducing vulcanization by means of radical reactions, such as peroxides. 3. Bifunctional compounds, among which phenol/formaldhyde derivatives seem to be the most interesting. Materials in the third group will be the object of this study.
Addition of Unsaturated Monomers to Rubber and Similar Polymers
Authors: Pinazzi C. , Danjard J-C. , Pautrat R. 
Published: February 2011

Abstract
The addition of different ethylene monomers to polyisoprene was studied in order to throw a light on reaction mechanisms and structures of reagents. It was attempted, during the planned transformations, to maintain as best as possible the shapes and sizes of initial macromolecules, upon which rests the property of high elasticity. For this purpose, it was decided to avoid grafting reactions, as well as any reactions affecting the nature of the polyisoprenic chain, e.g., scission, cross-linking, and cyclization. After the completion of the work carried out by one of the authors on the addition of maleic anhydride, the existence of two mechanisms was brought to light: the one is of a radical type, produced by adding an unsaturated reagent on a methylene close to a double bond of chain; the other is of a thermal nature, triggered by the action not of a catalyst, but of a rather high temperature. It is clear that the latter process does involve isomerization of a part of chain double bonds. The model to which maleic anhydride is connected has been deduced by examining the reaction aptitudes of a series of monomers. The major part of highly polymerizable materials, with the exception of acrylonitrile, were eliminated a priori, in order to avoid both homopolymerization reactions and graftings. The monomers in which double bonds are depleted in π electrons are more apt to give the desired reactions. The more favorable effect is obtained with α carbonyl (maleic anhydride and γ crotonolactone). Other factors were also taken into account. The work reviewed here enabled us to assess the way in which reactions evolve according to the considered mechanisms and produce new macromolecular materials. The resulting compounds have a high rubberlike elasticity and show a high chemical reactivity, due to anhydride or lactone side groups.