bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyisocyanates as Curing Adjuvants for Ethylene—Propylene Terpolymers
Authors: Wolfee J. R. , Albin J. R. 
Published: February 2011

Abstract
Ethylene—propylene—nonconjugated diene terpolymers yield vulcanizates of high modulus and tensile strength in the presence of strongly reinforcing fillers. In many applications where low cost, light color, or nonconductivity are required, it is necessary to use poorly reinforcing mineral fillers. The combination of poorly reinforcing mineral filler and amorphous EP terpolymer yields vulcanizates which do not have the excellent stress-strain properties characteristic of many black loaded stocks. The purpose of this paper is to present a new method of obtaining superior properties in mineral filled EP terpolymer vulcanizates.
The Analysis of Antioxidants and Accelerators in Rubber Compounds and Vulcanizates
Authors: Auler H. 
Published: February 2011

Abstract
In the rubber industry the number of accelerators and antioxidants has increased greatly in the last few years. Van Alphen even in 1956 described 154 accelerators and 87 antioxidants of different chemical structure. The detection of such a large number of materials, depending on their combination in stocks, is more or less difficult, although the detection of the presence of one or another compound often makes possible a prejudgment as to which other substances can be counted on and which cannot. Besides the chemically homogeneous accelerators and antioxidants, use is also made of mixtures as combination products. The individual components are qualitatively detectable in mixtures. Information on the type of these products is given by quantitative determination methods such as described by Zijp, Kortum, Szalai and Szöke, among others. The original substances are often chemically altered during vulcanization or later in the preparation of samples for testing; e.g., symmetrically constituted disubstitution products may split into monomers, substituents split off from the basic molecule, or reactions of various types take place which render the investigation difficult. The identification of antioxidants and accelerators received a great impetus from the application of chromatography which is of importance today as a method of separating the individual materials for subsequent physical determination methods. After Tswett has recognized decades ago the separating effect of absorption columns in the analysis of compounds of chemically similar structure, this method was used only much later for the Chromatographic investigation of rubber compounds. The earlier analytical methods in this field depend on the use of conventional methods, e.g., selective extractions and precipitation of the substances to be isolated, which are then identified in pure form by melting point determination.
Effects of Self-Diffusion and Inter-Diffusion in Polymer Systems
Authors: Voyutskii S. S. , Vakula V. L. 
Published: February 2011

Abstract
Diffusion of low-molecular substances in high polymers has been the object of study by many Soviet and other investigators during the past two decades. Included is the work of Reitlinger, Zhurkova, Ryskin, Malinskii, and Vasenin in the Soviet Union, and Barrer, Crank, Long, Auerbach, van Amerongen, McCall, Shtamm, and many other authors elsewhere. By way of contrast, the effects of self-diffusion in polymers and diffusion of polymer in polymer (inter-diffusion) have been given little study because of the great experimental difficulties and the complexity of theoretical explanations. Meanwhile, these effects have considerable scientific and practical significance. As will be seen hereafter, very many properties of polymers are associated in some manner with diffusivity of macromolecules or their segments. No less important is the tendency toward self- and inter-diffusion of polymers in processing and use. The aim of this review is to correlate data concerning self- and inter-diffusion of polymers containing elastic molecules (elastomers), available in several studies, and to suggest further paths for investigation of this problem.
Tack in Rubber
Authors: Bussemaker O. K. F. 
Published: February 2011

Abstract
The expressions tack, tackiness, and stickiness have been in use since the beginning of the rubber industry. During the years their meaning has changed considerably. The first occasion where tackiness was mentioned was in the case of crude natural rubber. The surface of the rubber became tacky or sticky during storage. This phenomenon has been thoroughly discussed in the literature. As a general conclusion it was accepted that both oxidation and depolymerisation occurred. Three factors were reported to be the cause of these processes: light, traces of copper, and manganese. From our point of view we would call this effect stickiness, as we are only interested in the building tack of rubber. In the period when the only rubber was natural rubber and high loadings of highly active fillers were not generally used in compounds, building tack was no problem. Building tack was first mentioned in a publication by Griffith and Jones in 1928. They started their experiments by measuring tack in their search for methods to prevent cotton liners from sticking to unvulcanized rubber. One would have expected much work on the measurement and improvement of tack in Germany and Russia during the development of synthetic rubbers. However, this only proved to be the case in Russia. The first publication available was the translation of an article by Voyutskii and Margolina in 1957. From Voyutskii's work we were able to trace the first article in 1935 by Zhukov and Talmud, who studied the adhesive power of synthetic rubber. In the USA the first theoretical approach to the subject was by Josefowitz and Mark in 1942, who at that time did not realize the difference between stickiness and tack. This difference became clear when lack of tack became the big problem in the use of synthetic rubber. In many cases it was found that addition of resins and softeners gave a very sticky compound which had no building tack at all. The tack problem was first discussed at the ASTM symposium on the application of synthetic rubbers in 1944 by Juve who gave a definition of building tack. From that time, the problem has been studied regularly, especially from the practical side, to find ways and means to improve the building tack of synthetic rubbers.
Characterization of Viscoelastic Behavior of Stereoregular Poly(Isoprenes) by Relaxation Experiments
Authors: Szilagyi L. , Riccò T. , Danusso F. 
Published: February 2011

Abstract
The mechanical relaxation of twelve samples of unvulcanized cis poly-(isoprene)s, including both natural and synthetic polymers, was studied over a range of temperatures. Master curves of relaxation modulus obtained from these data were used to derive relaxation spectra according to linear viscoelastic theory. A recent theory was used to calculate mean values of quantities related to the supermolecular structure which occurs spontaneously in these materials and is responsible for their viscoelastic properties. This structure is schematized in a model consisting of a system of macromolecules which interact with each other by elastic forces and frictions corresponding to points of entanglement between chains. The analysis leads to the determination, for each sample, of the number of entanglements per molecule, the physical network density, the value of relaxation parameters, and the relationship of each of these quantities to molecular weight.
New Methods for Electron Microscopy of Polymer Blends
Authors: Smith R. W. , Andries J. C. 
Published: February 2011

Abstract
Two new methods of sample preparation have been developed for electron microscopical examination of polymer blends. The first is an ebonite method where the blend is hardened in a sulfur-sulfenamide-zinc stearate mixture and then microtomed. The second is a cryogenic method where the blend is microtomed in the frozen state and then stained with osmium tetroxide. These methods have been used to examine styrene—butadiene rubber/cispoly (butadiene), natural rubber/ethylene propylene diene monomer rubber, NR/trans Polypentenamer blends, and a NR/starch mixture. Sharp, clear phase differentiation is obtained with all blends studied. SBR/PB blends were obtained when the viscosities of the blended polymers were similar. Similarity of molecular structure, increased milling time, and increased milling temperature also decreased the zone size of the dispersed phase. A three-phase system was observed when a high-styrene SBR was blended with PB ; the third phase consists of block poly (styrene) embedded in the SBR phase. Under all conditions SBR/PB blends were found to be heterogeneous, with no evidence of a single homogeneous phase.
New Types of Premature Vulcanization Inhibitors
Authors: Hopper R. J. 
Published: February 2011

Abstract
The activity of the thiosulfonamides and dithiotrichloromethanes as retarders is apparently a result of their ability to function as BTSH trapping agents. The effect of substituents on retarder efficiencies seems consistent with a mechanism involving a three-way competition between crosslinking, retardation, and decomposition of retarder to non-functional products. The key reaction responsible for trapping BTSH probably involves a nucleophilic displacement. Substituents which favor this type of displacement increase efficiency when they are on the portion of the retarder molecule which combines with BTSH; when they are on the portion which becomes the leaving group, they evidently promote decomposition, causing a net decrease in retarder efficiency.
Studies on MBT-Accelerated Sulfur Vulcanization of Natural Rubber Reinforced with Carbon Black
Authors: Bhoumick S. , Banerjee S. 
Published: February 2011

Abstract
Studies have been made on the mechanism of MBT accelerated sulfur vulcanization of natural rubber containing semi-reinforcing carbon black as a filler. DCP has been used as an aid to distinguish between free radical and polar mechanism. Results indicate that sulfuration by MBT and sulfur proceed by a free radical mechanism but it becomes polar when ZnO and stearic acid are also present. Carbon black does not interfere in the sulfuration but it gives rise to additional crosslinks.
Studies on Dicumyl Peroxide Vulcanization of Styrene—Butadiene Rubber in Presence of Sulfur and 2-Mercaptobenzothiazole
Authors: Das C. K. , Banerjee S. 
Published: February 2011

Abstract
The effect of sulfur, MBT, zinc oxide, and stearic acid on the DCP vulcanization of SBR has been studied. DCP decomposition obeys first order kinetics in all cases, but its rate constant is higher in presence of MBT. Sulfur and MBT reduce the crosslink density due to DCP. In the mixes containing sulfur, MBT, zinc oxide, and stearic acid in presence of DCP the crosslink density is initially additive. Here oxidation of some pendent vinyl groups are effected by DCP, and these groups also take part in thiol addition reaction with MBT. The thiazole accelerated sulfuration of SBR proceeds fundamentally by the same mechanism as reported for NR, but the details show slight difference chiefly due to the presence of pendent vinyl groups and styrene units in the chain and due to the absence of pendent methyl groups in SBR.
Radiation Chemical Conversions in Fluorine Containing Elastomers under Different γ-Irradiation Conditions
Authors: Kryukova A. B. , Kuz'minskii A. S. , Gilinskaya N. S. , Galil-Ogly F. A. , Sankina G. A. 
Published: February 2011

Abstract
Rates of radiation chemical crosslinking and scission of fluorine containing elastomers based on copolymers of vinylidene fluoride with trifluorochloroethylene (Copolymer 1), with hexafluoropropylene (Copolymer 2), and with a perfluoroalkyl vinyl ether (Copolymer 3) and also the behavior of their radiation vulcanizates in the stressed state at high temperatures are determined both by the type of polymer and by the irradiation conditions. Crosslinking rates of Copolymers 2 and 3 are higher than those of Copolymer 1; oxygen of the air inhibits crosslinking by γ-radiation; by irradiation in the presence of oxygen of the air, the sol fraction is 8–10 times higher than in its absence, Copolymer 3 vulcanizates obtained by irradiation in the absence of air appear to be optimal.
Dependence of the Polymer-Solvent Interaction Parameter of Vulcanizates Based on Cis-1,4-Poly(Butadiene) on the Type and Concentration of Vulcanizing Agent
Authors: Gavrilov V. M. , Shvarts A. G. 
Published: February 2011

Abstract
Values of the polymer-solvent interaction parameter were obtained for cis-1,4-poly(butadiene) vulcanized with alkylphenol—formaldehyde oligomer, sulfur, and peroxide systems swollen with heptane, benzene, and m-xylene. The dependence of the interaction parameter on the degree of crosslinking was demonstrated. The method of vulcanization does not affect the dependence of χ on υr for good solvents, but influences this dependence for n-heptane, a weak solvent. It was shown that the better the solvent, the stronger the dependence of the interaction parameter on the degree of crosslinking.
Force—Deflection Relations for a Model Air Spring
Authors: Gent A. N. , Thomas A. G. 
Published: February 2011

Abstract
Force—deflection relations are derived for a model air spring consisting of two long rigid plates connected at their edges by flexible membranes and containing air under pressure. Compressive, tilting, and shear deflections are considered. Compressive forces are evaluated for three representative conditions: an isolated spring; one connected to an auxiliary reservoir of equal volume; and one with the internal pressure maintained constant. Corresponding membrane tensions and elongations are calculated. Tilting and shear load-deformation relations are specialized to the case of small deflections in order to deduce the corresponding stiffnesses. Compression of a relatively thin circular air spring is also treated. Attention is drawn to a number of potential instabilities.
Filler Aggregates and Their Effect on Reinforcement
Authors: Medalia A. I. 
Published: February 2011

Abstract
The most highly reinforcing fillers, namely carbon blacks and silicas, consist of aggregates of quasi-spherical particles fused together. In the absence of direct experimental studies with single-particle carbon blacks or silicas of high surface area, we cannot be sure if aggregated structure is essential for good reinforcement, or whether aggregation and fusion just happen to accompany the formation of fine particles at practical concentrations. In any case, there is no doubt that the aggregate nature of the filler plays a major role in determining the properties of the rubber compound. Here I would like to review what we know about filler aggregates, especially of carbon black, and suggest some mechanisms for their effects on rubber; and also indicate where our knowledge seems inadequate at the present time.
Tire Cord Dip Pick Up by Atomic Absorption Spectroscopy
Authors: Firkins J. L. 
Published: February 2011

Abstract
Graphite furnace atomic absorption spectroscopy has been used to develop a quick and accurate test for tire cord dip pick up. Strontium nitrate solution is added to either predips or resorcinol-formaldehyde latex dips at predetermined levels of a few parts per million. Sufficient replicate analyses of one to three milligram samples of treated cord can be run to provide reliable data on both the absolute level of dip pick up and the short term uniformity of the dip. The technique offers substantial advantages in both turn-around time and total analysis time relative to wet gravimetric techniques in current use.
Particle Size Determination of Tire-Tread Rubber in Atmospheric Dusts
Authors: Cardina J. A. 
Published: February 2011

Abstract
Ambient dust was sampled with an Andersen high volume sizing impactor within twenty feet of heavy traffic on the Akron expressway and analyzed for tread rubber by pyrolysis gas chromatography. Methods were developed for removing dust particles from the collection surface and preparing them for pyrolysis. Those particles which lie in the respirable range 1.1 to 7.0 microns constitute 25 to 40 per cent of the total by weight. The remainder is divided about equally between the size range above 7.0 microns (not respirable) and those below 1.1 microns, i.e., about one-third of the dust lies in each size category. The amount of tread rubber in these respirable dusts as determined by styrene, dipentene, and vinylcyclohexene in their pyrolyzates varied from 1.5 to 9.2 per cent with an overall average of 4.3 per cent. In the size range above 7.0 microns a high value of 13.1 per cent rubber was found with an average of 6.3 per cent. In terms of micrograms per cubic meter of suspended particulates in the respirable range 1.1 to 7.0 microns, the values for tread rubber ranged from 1.0 to 4.9 with an average of 2.6. The low potential for health hazards from this respirable dust can be appreciated from a comparison with safe levels (TLV's) for certain pollutants known to be highly toxic as follows: Beryllium—2, lead compounds—150, mercury alkyls—10, cristobalite—50.
Dynamic Mechanical and Electrical Properties of Vulcanizates at Elongations up to Sample Rupture
Authors: Voet A. , Morawski J. C. 
Published: February 2011

Abstract
Dynamic properties of vulcanizates have been measured at small and large extensions, up to specimen rupture, by means of a modified Rheovibron. The influence of temperature, frequency, and amplitude on the dynamic moduli has been determined for a number of SBR samples, uncharged or charged with silica or carbon black. A study has been made of the dynamic Mullins effect (stress-softening) and of dynamic stress-relaxation for various charged and uncharged samples. Electrical conductivity has been determined simultaneously with dynamic properties for carbon-black loaded elastomers. The gradual reformation of a previously destroyed secondary filler network could be followed quantitatively in rate and magnitude at very low frequencies. It appears that at small deformations a secondary, reversible filler network plays an important part in the dynamic properties of the vulcanizates. At intermediate deformations, however, this network has been eliminated. Conductance data of carbon-black loaded vulcanizates indicate a phenomenon of orientation of anisometric aggregates. At still higher deformations irreversible changes are observed, pointing to a rupture in filler—elastomer bonds as well as of elastomer chains, two experimentally distinguishable phenomena.
Raman Spectral Studies of 2-Mercaptobenzothiazole Accelerator Systems
Authors: Kapur R. S. , Koenig J. L. , Shelton J. R. 
Published: February 2011

Abstract
A mechanism for the formation of the rubber-bound intermediate in the vulcanization of elastomers has been proposed. The active sulfurating agent is a polysulfide. Laser Raman spectroscopy has been used to provide significant evidence for this mechanism in the presence of cis-1,4-poly(butadiene).
Radiation Curing of Ethylene—Propylene—Diene Elastomers
Authors: Eldred R. J. 
Published: February 2011

Abstract
A significant reduction of the radiation dose required to cure EPDM elastomers can be obtained by introducing crosslinking monomers into the compounds. Multifunctional acrylates are more efficient than either allylic or pendent-vinyl crosslinking agents. The curing rate is also affected by the nature of the unsaturation in the base polymer. Compounds of EPDM containing 5-ethylidene-2-norbornene are more reactive than those with 1,4-hexadiene. Increasing polymer unsaturation levels above 3 per cent or changes in ethylene—propylene ratios have little effect. Curing rate is dependent, however, on the Mooney viscosity of the elastomer, with higher viscosities yielding faster cures. The addition of extender oils drastically reduces radiation efficiency, which depends on both the nature and the level of the oil. This can be overcome by increasing the monomer content. The physical properties of radiation-cured EPDM compare favorably with those of sulfur-cured EPDM. The radiation-cured EPDM exhibits greatly improved compression set and oil resistance.
The Effect of Structure Breakdown of Carbon Black on Rubber Properties
Authors: Boonstra B. B. , Dannenberg E. M. , Heckman F. A. 
Published: February 2011

Abstract
Mechanical processing of carbon blacks by a novel pressure-milling technique provides a controlled breakdown of primary carbon-black aggregates. In contrast, direct compression has a much smaller effect on aggregate size. In rubber vulcanizates, the pressure-milled carbon blacks give about the same vulcanizate properties as normal carbon blacks with the same void volume or DBP absorption value. Breakdown of aggregates occurs during the process of incorporating and dispersing carbon black in rubber. The retention of average aggregate size after mixing in rubber is in the range of 60–70 per cent for Vulcan M (N339), a new technology tread black. We have shown that the DBP absorption method cannot distinguish between loss in void volume by compaction of aggregates versus the actual breakdown of aggregates. The sedimentation method by centrifuging provides a means for measuring aggregate size independent of the original packing of the dry black. In order to carry out these studies, a number of new experimental techniques were used. These include: a) controlled aggregate size breakdown by pressure-milling. b) Stokes diameter distribution measurements by centrifuging aqueous dispersions in a Joyce Loebl apparatus. c) Quantimet analysis of projected aggregate areas from electron micrographs from specially prepared solvent dispersions of rubber-carbon black samples where the aggregates are clear of interference from adhering rubber. It has been shown for the first time that for both Vulcan M (N339) and Vulcan 6 (N220) the median Stokes diameters, DSt, obtained by the centrifuge method and the equivalent sphere diameter, De, from Quantimet projected image analysis are in the range of 123–153.
Spin-Label Investigation of Polyurethane Networks
Authors: Ward T. C. , Books J. T. 
Published: February 2011

Abstract
Two types of polyurethane networks were examined using the spin-label technique. Nitroxide free radicals which are stable under moderate conditions were covalently attached to the network chains of amorphous polymers based on (1) poly(tetramethylene glycol), p,p′-diphenylmethane diisocyanate (MDI), trimethylolpropane, and (2) ethylene glycol, MDI, glycerine. Polymer (1) had very low “hard block” content, polymer (2) a very high content. Mechanical properties and differential thermal analysis measurements were made on polymer (1). Electron spin resonance spectra of the samples were obtained in the unstrained, strained, and swollen states. Large differences in the spectra were observed, depending on chemical composition, temperature, and state of swelling. Transitions from “frozen” to “rapid motion” type of spectra occurred at 70° for polymer (1), at −10° for polymer (1) swollen to equilibrium, and were unobserved up to 150° for polymer (2). Since the nitroxide label was necessarily adjacent to MDI units, was present in very small concentrations, and experienced no alterations in environment as “soft segments” did, then it is suggested that the spin-label technique is a valuable tool for analyzing microstructure of pseudoamorphous systems.