bluuebunny/crossref_metadata_2025 huggingface dataset:
N-(Aminothio)imide Cure Modifiers
Authors: Lawrence J. P.
Published: February 2011

N-(Aminothio)imides have been found to influence the cure characteristics of diene rubbers accelerated by conventional vulcanization accelerators. In this respect, they generally act both as scorch inhibitors and activators to increase the cure rate and crosslink density. The ability of these compounds to act as scorch inhibitors is believed to be attributable to trapping of MBT with resultant formation of the corresponding free imide and 2-(aminodithio)benzothiazole. The latter is an active vulcanization agent and may lead directly to the formation of pendent accelerator groups and free amine, likely the source of the cure activation. As precursors to crosslink formation, the pendent accelerator groups carry an atom of sulfur derived from the cure modifier and thus lead to higher crosslink density. The relative scorch inhibiting characteristics are influenced by the basicity of the parent amine and thermal stability of the cure modifier. The compounds derived from amines of weaker basicity are better retarders and less subject to thermal degradation which would lead to nonretarding products. The relative cure activating effects are apparently influenced by both steric and electronic effects of the parent amine. Cure activation increases as the steric bulk decreases and basicity increases. As expected, the nature of the imide substituent played a relative insignificant role in influencing the cure characteristics, aside from a possible stabilization against thermal degradation.
The Volatile Products Evolved from Fluoroelastomer Compounds during Curing
Authors: Pelosi L. F. , Moran A. L. , Burroughs A. E. , Pugh T. L.
Published: February 2011

The data show that hydrogen fluoride is not a major component of the gases evolved during any stage of the cure. During the press cure the major components are CO2 and H2O. Temperature and mold openings can have a significant effect on the weight loss during press cure. During the postcure the major components are H2O and CO2, while the rest of the components result primarily from the curing agents. No fluorocarbon breakdown products were detected. A variety of factors can affect the nature of the products evolved from fluoroelastomer compounds during curing. Since the physiological effects of many of these compounds are not known, it is recommended that adequate ventilation always be used when curing fluoroelastomers.
Spectroscopy in the Rubber Industry
Authors: Westfahl J. C.
Published: February 2011

The kinds of spectroscopy to be discussed in this review are those which yield organic structural information and involve the nondestructive interaction of electromagnetic radiation with polymers of interest to the rubber industry. For those forms of spectroscopy which meet this rather restrictive definition, their use with nonpolymeric compounds of importance to the rubber industry will be included. In accord with these criteria, proton magnetic resonance (PMR), carbon-13 magnetic resonance (CMR), electron spin resonance (ESR) and ultraviolet (uv) spectroscopy will be discussed in this review. Infrared spectroscopy, which is of great importance to the rubber industry, has been the subject of a recent Rubber Review by R. W. Hampton and will therefore not be reviewed here. Using this definition, mass spectrometry will not be discussed, since it cannot be applied to polymers without first fragmenting them by pyrolysis. X-ray fluorescence spectroscopy is extremely useful for detecting and measuring metallic impurities in polymers (elements of atomic weight greater than A1). Because the polymers of this review are composed largely of elements lighter than Al (C, H, N, O), x-ray fluorescence is not useful for the study of the polymer itself. This is largely true also for x-ray diffraction (XRD) where noncrystalline polymers yield XRD patterns characteristic of liquids, which can yield information from which the average distance between molecules can be calculated. For partly crystalline polymers, XRD yields information from which the extent of crystallization, the size of polymer crystallites and their arrangement in the bulk polymer can be calculated. This morphological information goes beyond the basic organic structure of interest to organic chemists, and x-ray spectroscopy will not be discussed in this survey.
Elastomers in the Automotive Industry
Authors: Walter G.
Published: February 2011

This paper sets out to demonstrate the present status of elastomer usage in passenger and commercial vehicles and at the same time to enumerate the requirements of the various components. As clearly shown, elastomers play a major role in car design, so important in fact, that considerable research and development has been devoted to the improvement of individual elastomer components. This is illustrated by the considerable fundamental work in material science, the associated establishment of test specifications, and the comparison of material requirements as known from practical experience and the performance patterns of the various elastomers. With reference to the application of individual elastomers for specific purposes, it has been indicated how the development of certain materials has slowed down, while further progress is still feasible with others. To do so, will require considerable effort on the part of the automotive and rubber industries.
Heat Generation in Pneumatic Tires
Authors: Kainradl P. , Kaufmann G.
Published: February 2011

A review of the entire literature on heat generation in tires shows that, while a considerable number of articles have reported the effect of running conditions, only the few cited here have provided clarification of the causes of heat generation. The overview presented here also has limitations in some respects, especially in that all the reported regression equations (except those for radial passenger car tires) have a large residual term. This is due to the scattering of the test results and the fact that only the viscoelastic properties of the tread and carcass stocks were varied, but not the tire cord and the other vulcanizates used. Tire cord properties have fixed properties, as far as the tire specialist is concerned and cannot be changed. A further regret is that almost all the investigations were carried out on laboratory test wheels, so that no experimental findings obtained from tires run on the road are included. This is so because road experiment conditions are difficult to make reproducible. On the whole, one can expect that the reported results would be qualitatively valid for tires run on the road, but the differences among different tire designs would probably not be as great, while surface friction effects would be more significant. Moreover, though the tire test parameters were different in the different laboratories, they remained constant in each test. No attempt was made to establish dependence on the load (except by Wesche), the internal pressure, the speed, the radius of the test wheel, etc., because each individual tire specialist is confronted, within his own development team, by certain standardized test conditions. The tires have to reach a sufficiently long running time under these conditions. Hence, they may not exceed certain limiting temperatures. Modifications of such requirements were not included in the scope of the present series of experiments. Almost all the authors took test samples for the measurement of viscoelastic properties from the tires, since correlations with laboratory-prepared test pieces were usually poorer. Nevertheless, in the course of compound development the tire chemist is forced to rely on laboratory test specimens and must establish relations to their properties. Consequently, the causes for the differences have to be elucidated for each individual case. In spite of these limitations, the state of the art, as presented here, permits reliable estimates to be made of the changes in tire running temperature that are caused by given changes in the recipes of the tire component stocks.
Fourier Transform Infrared Studies of the Mechanism of Oxidation of Cis-1,4-Polybutadiene
Authors: Pecsok R. L. , Painter P. C. , Shelton J. R. , Koenig J. L.
Published: February 2011

The thermal autoxidation of cis-1,4-polybutadiene was studied by FTIR at various temperatures. The spectral information obtained gives more details of the autoxidation than was previously available by dispersive infrared spectroscopy. The primary mechanism involves both cyclic alkoxyperoxides that had been previously suggested by Bevilacqua and Bolland, respectively. We have demonstrated that the loss of cis and the formation of trans structures at 25° and 60°C is an oxidative process.
The Reaction of N,4-Dinitroso-N-Methylaniline and Polymers
Authors: Morita E.
Published: February 2011

Both nitroso groups participate in the reaction of N,4-dinitroso-N-methyl-aniline (DNMA) with various polymers, and the pathways of the reaction are influenced by the reaction conditions. In dilute solution the rate of the reaction is proportional to the amount of unsaturation present and is pseudo-first order with respect to DNMA at elevated temperature with or without polymers present. The iV-nitroso group undergoes thermal fission liberating nitroxyl and N-methyl-p-nitrosoaniline free radicals. The presence of hydrocarbons with labile hydrogen accelerates the hydrogen abstraction by the amine free radical to form N-methyl-p-nitrosoaniline and a hydrocarbon free radical, which may combine with another amine free radical to form a hydrocarbon with pendent N-substituted-N-methyl-p-nitrosoanilme group. The 4-nitroso group of DNMA adds to the double bond, leading to the formation of an adduct with N-methyl-N-nitroso-p-phenylenediamine pendent group. Depending on the reaction conditions, the 4-nitroso groups may form azoxy compounds or may be oxidized to nitro groups. The bifunctionality of DNMA leads to the formation of crosslinked polymers or to chemical promotion of carbon black reinforcement with N, N′-disubstituted-N-methyl-p-phenylenediamine type crosslinks.
Effects of Rubber-Curing Chemicals on Tensile Strength of Polyester Yarns
Authors: Weigmann H-D. , Lamb G. E. R.
Published: February 2011

The degradative effects of accelerators of the sulfenamide and thiuram types on polyester tire yarns depends on the stability of the accelerator and the reactivity of the amines generated. Thermal decomposition of the accelerator alone is not sufficient to explain the degradative effects reported by other workers. The complexes formed by the accelerators in the presence of activators, such as zinc oxide and stearic acid, have lower thermal stability than the accelerators alone and release amines at lower temperatures. The formation of the complexes can be shown by differential scanning calorimetry. The findings of this investigation may have important implications with regard to the release of amines during the life of a tire and to the efficient compounding of rubber stock. If, as it appears, the decomposition of TMTM and TBBS occurs more efficiently if they are previously allowed to form a complex, there may be advantages in forming such complexes before addition of the ingredients to the rubber stock. If the ingredients are added separately, the formation of the complex would be controlled by diffusion of the ingredients in the rubber, and incomplete complex formation may result, leaving residues of unreacted components. These would, over a period of time, release more amine, causing degradation of the polyester cord. Advantages of prior complex formation, beside reduction of the above effect, might be lower concentration requirements for the accelerator and possibly better long-term physical properties of the elastomer. As pointed out in the introduction, effects of moisture, which were discussed by Iyengar, were not taken into consideration in this investigation. The conclusions drawn here are therefore strictly applicable only to the thermal decomposition of the accelerators and accelerator-activator complexes. This mode of decomposition is, however, felt to be of major significance for the degradation of polyester tire cords in truck tires during actual use.
The Third Dimension of Carbon Black Structure
Authors: Mercer H. N. , Boyer A. H. , Bhusky P. L. , Deviney M. L.
Published: February 2011

Structure is probably the most difficult characteristic of carbon black to define. Electron microscopy has shown that the individual particles of a black are fused together into a variety of shapes, collectively defined as the structure. Here, particle is used to refer to that entity which is somewhat spherical in shape and is the smallest “building block” of structure. These particles have also been called “domains” of rotational graphitic layers and “nodules”. The larger unit resulting from the fusion of these particles forms an “aggregate” or a “primary structure” unit. A collection of aggregates, held together by some other force (e.g , van der Waals force), is called an “agglomerate” or “secondary structure”. With dry black, it is difficult to completely eliminate all secondry structure. However, main emphasis in this study was on primary structure, because it has the greater influence on rubber properties and because secondary structure is greatly reduced in good rubber mixing. Many recent characterization studies have been concerned with making direct measurements on primary structure units (aggregates) by automated image analysis techniques, a pencil following device, and a comparative chart method. In the work described here, a different approach has been taken to viewing carbon black primary structure units, an approach using the scanning electron microscope combined with stereoscopic methods. This initial report will be mainly concerned with a description of the techniques and results on several individual primary structure units. It is suggested that the efforts described here provide a realistic view of carbon black primary structure and that a third dimension term is essential for primary structure characterization.
Radial Tire Cord-Rubber Composites
Authors: Patel H. P. , Turner J. L. , Walter J. D.
Published: February 2011

Experimental and theoretical results are presented in terms of the elements of the compliance matrix for the material properties which are needed to characterize a calendered ply of various cord-rubber composites commonly used in the body and belt of radial tires. It is shown that a single ply can be represented as a linear, elastic, homogeneous, orthotropic material to a level of accuracy sufficient for modeling inflated, but otherwise unloaded, radial tires. Cord load distributions in the body, belt, and turnup ply endings are predicted and plotted from the bead to the crown of inflated radial tires using principles of structural mechanics to represent the laminated material properties of the tire and finite element techniques to calculate the stresses in the cords. Predictions are also made for rubber strains and tire growth at the crown due to inflation pressure loading. The effects of changing various tire construction and/or material property parameters on such responses are assessed; these predictions are shown to be in reasonable agreement with experimental measurements.
Elongation of Painted High-Modulus Elastomers at Low Temperatures
Authors: Djiauw L. K. , Fesko D. G.
Published: February 2011

The paint film thickness and its elongation strongly affect the ultimate elongation of a painted elastomer. Thus, it is of utmost importance, in testing these materials, whether for component design or for material development, that the thickness of the paint be known and controlled. It is also important to note whether multiple cracks are present. Further, although low-temperature elastomers may display relatively high elongations even in the presence of paint cracks, elastomeric paints with greater low-temperature elongations are needed for available substrates to sustain higher deformations.
Studies of Heat Generation in Polyester Cord Tires
Authors: Lamb G. E. R. , Weigmann H-D. , Goswami B. C.
Published: February 2011

Measurements of loss factor in polyester cord and cured rubber stock were made. From the results, the equilibrium cord temperatures in a rotating tire were estimated. These calculated values agree with measured values reported in the literature. It is shown that, for truck tires, cord temperatures can easily rise to levels where cord degradation in the presence of sulfenamide accelerators is known to occur. Measurements on cords which had been degraded by aminolysis indicate that loss factors increase as a result of the degradation and cause significant increases in local steady-state temperatures. This effect will tend to accelerate the rate of degradation at those locations. The increases in loss factor agree with observations on loss factors at increasing levels of crystallinity in polyester fibers in the literature.
Mechanical Properties of Short-Fiber-Elastomer Composites
Authors: Moghe S. R.
Published: February 2011

The reinforcement of rubber compounds with short fibers has, at times, become necessary in many product applications. Particularly compounds with relatively low fiber content have proven successful in improving hose and belt performance. This is mostly due to an increase in composite stiffness without a great sacrifice of basic processability characteristics of the compound. Too large a fiber content becomes a primary source of difficulties during manufacture and/or product performance. Therefore, an understanding of how various composite properties depend upon fiber and matrix properties, as well as on fabrication methods, will help design better products. The mechanical properties, such as modulus, strength, and ultimate elongation depend upon fiber orientation, aspect ratio, and adhesion between fiber and matrix compound. Unfortunately, the degree and type of adhesion cannot be estimated quantitatively at present even though its importance in the improvement of composite properties is well recognized. Aspect ratio is another parameter which can be used in improving composite properties. As a rule, a higher aspect ratio gives higher composite stiffness. During processing, fibers are buckled and crimped under large deformations, which results in a distribution of fiber lengths, rather than a constant length as before mixing, as shown, for example, in Figure 1. One can, therefore, expect to achieve the same composite properties regardless of the initial fiber length (up to, say, 15 mm) or fiber length distribution. Of the three parameters, fiber orientation affects composite properties the most. During processing (milling, extrusion, etc.) of rubber composites, the fibers tend to orient along the flow direction, causing mechanical properties to vary in different directions. Therefore, by changing or suitably controlling the flow direction, optimum properties can be generated for a given product. A good example is the balanced fiber orientation in a hose which gives optimum design strength. Milling or calendering is perhaps the most commonly used processing method in which fibers tend to orient along the mill direction. Since each mill or calender differs from any other in size, roll speed, and other characteristics, it is essential to determine the influence of these parameters on composite properties. Results of a systematic study to identify significant mill parameters which influence the composite properties are presented here.
A Broad-Line NMR Investigation of Isoprene Rubber Filled with Carbon Black
Authors: Svensson L. G. , Svanson S. E.
Published: February 2011

The results of NMR measurements on IR filled with various carbon blacks lead to the following conclusions. The rubber matrix is a heterogeneous system characterized by two rubber phases of different chain mobilities. One phase is almost similar to unfilled IR at the temperature of measurement, while the properties of the other are nearly identical to those of pure IR at a lower temperature. The following observations apply to the phase with restricted mobility : 1. The quantities of rubber and carbon black in this phase are proportional below a critical loading, which supports the assumption that immobilization is limited to the immediate surroundings of the filler aggregates. The critical loading varies with structure and defines the packing density above which the formation of a coherent gel becomes important. 2. The rubber content decreases with rising temperature, showing that the activation energy for the onset of segmental motion varies within the phase. The mobility of the rubber chains directly bound to the surface is restricted even far above the glass transition temperature. 3. The degree of immobilization varies with temperature but is mostly independent of carbon black type and loading. 4. The actual distribution of immobilized rubber within an aggregate is not completely known, but some evidence exists for the immobilization of a thin surface layer as well as parts of the occluded rubber. A considerable immobilized rubber fraction is independent of surface area and structure.
A New Derivation of Postgel Properties of Network Polymers
Authors: Miller D. R. , Macosko C. W.
Published: February 2011

The probability of a finite or dangling chain on an ideal polymer network has been derived by a simple recursive scheme. In contrast to the method of Dobson and Gordon, probability generating function formalism is not required. The general result, Equations (21), and its specific solutions, Equations (23), (24), and (30), give the finite chain probability as a function of reactant type and extent of polymerization. They cover most of the important types of network forming polymerizations. From the finite chain probability, useful property relations such as sol fraction, crosslink density, and the number of elastically effective network chains are developed. Because of their simplicity, we expect these relations to be further developed and applied to network polymer property measurements.
The Effect of Network Structure in the Equation of Rubber Elasticity
Authors: Valles E. M. , Macosko C. W.
Published: February 2011

Though the stress, strain, and temperature dependence for an ideal rubber is fairly well established, the relation between network structural features like crosslinks, dangling ends, and entanglements and mechanical response is uncertain. The modulus-structure relations recently derived by Miller and Macosko for several types of networks are tested here with a model system: the hydrosilation crosslinking of vinyl-terminated polydimethylsiloxane chains with a tetra-functional silane. Results of shear modulus as a function of extent of reaction and of stoichiometric imbalance are in good agreement with the theory.
Randomly Branched Polymers. I. Hydrodynamic Properties
Authors: Kurata M. , Abe M. , Iwama M. , Matsushima M.
Published: February 2011

A sample of copolymer of styrene and 1,4-divinyl-2,3,5,6-tetrachloro-benzene was prepared and fractionated. Using the fractionated copolymers, effects of chain branching on the intrinsic viscosity and sedimentation coefficient were studied experimentally. It was found that in both theta and good solvents, the intrinsic viscosity of the branched polymers obeyed a new semi-empirical relationship, [η]b=g0.6[η]l. Here [η]l is the intrinsic viscosity of a linear polymer having the same molecular weight as the branched one, and g is the contraction factor which is defined as the ratio of the mean-square radii of gyration between the branched and linear polymers, i.e., g=〈S2〉b/〈S2〉l. It was also found that the sedimentation coefficient in theta solvent agreed with the theoretical value obtained by Kurata and Fukatsu. The degree of branching estimated from the intrinsic viscosity or sedimentation coefficient was in close agreement with the value estimated from consideration of the copolymerization kinetics.
The Structure and Relaxation of Thin Polymer Layers on Solid Surfaces
Authors: Lipatov Y. S.
Published: February 2011

In conclusion, we can say that the properties of thin polymer films and their relaxation behavior are strongly dependent on their thickness. This is related to the restriction of molecular mobility at the phase boundary (independent of its nature) as a result of the reduced number of possible chain conformations. The less the polymer thickness, the more pronounced is the contribution of surface layers with diminished molecular mobility to the mechanical properties. This statement may be illustrated by Figure 12, which shows the dependence of the elastic modulus and surface-to-volume ratio on film thickness. Diminishing film thickness leads to increase in film rigidity, beginning at the point where the surface-to-volume ratio increases sharply. This suggests that the effect is associated with change in mechanical properties of thin surface layers, which contributes significantly to total mechanical properties. We have other data which show also that the relaxation spectrum of a film is changed when its thickness changes. The findings discussed above indicate that the solid surface has a noticeable and complex effect on the properties and relaxation behavior and relaxation time spectra of polymer coatings on solid surface, both inorganic and organic. The principal reasons for these changes are the adsorption interaction with the solid surface, decrease of molecular mobility, and strong intermolecular interaction transferring the influence of the solid surface to more remote layers of polymer.
Solvent Crack Growth in NBR Rubber
Authors: Nakashima K. , Manabe K.
Published: February 2011

The solvent crack growth of rubber compounded with various carbon blacks or calcium carbonate was investigated. It was found that the rate of crack growth of filler-loaded rubber was linearly related to extension ratio in a manner similar to gum vulcanizates. The rate of crack growth passes through a minimum as the filler loading is increased. It is dependent on the particle size of the filler; smaller particles show much greater effect than coarser ones. When the rates of crack growth of highly loaded samples were plotted against the extension ratio, plots consisting of two straight lines with a bending point were obtained. It was found that the extension ratio at the bending point depended upon the loading and particle size of filler. It was a linear function of the square root of the distance between filler particles. The slope of the line above the bending point varies with type of filler: with carbon black the slope is steeper; with calcium carbonate it is less steep.
Recent Developments in Urethane Elastomers and Reaction Injection Molded (RIM) Elastomers
Authors: Frisch K. C.
Published: February 2011

The chemistry and technology of urethane elastomers has advanced rapidly since their inception in Europe in the late 1930'a and early 1940's. The earliest elastomers were Vulkollan, developed by I. G. Farbenindustrie (IGF) and Vulcaprene, developed by Imperial Chemical Industries (ICI). IGF developed a casting process for Vulkollan, while the processing of Vulcaprene was carried out on conventional rubber equipment. While these elastomers were crosslinked, new types of urethane elastomers were developed which were thermoplastic in nature and allowed processing by means of conventional thermoplastic processing equipment. Urethane elastomers were also developed in various other forms such as latices, solutions in organic solvents, poromeric sheets, spandex fibers, sealants and caulks (consisting generally of low modulus elastomers), and expanded or micro-cellular elastomers. Omitting spandex fibers and poromerics, urethane elastomers can be classified according to the method of processing by which they are produced:
Measurement of Rubber Cutting Resistance in the Absence of Friction
Authors: Lake G. J. , Yeoh O. H.
Published: February 2011

A method for assessing the resistance of rubbers to cutting by sharp objects is described. It involves the application of the cutting implement—a razor blade—to the tip of a crack in a stretched tear test piece. The method enables effects of friction on the cutting process to be substantially eliminated. Under these conditions two distinct forms of cutting are observed : one is a slow time-dependent process, while the other involves rapid, “catastrophic” failure. Effects of test piece shape and deformation on the cutting behavior can be taken into account by use of fracture mechanics. The relative cutting resistance of different rubbers is found to vary according to the test conditions. At low deformations the onset of catastrophic cutting can be defined by a simple relationship applicable to all rubbers examined.
Model Compound Vulcanization—Part V. The Effect of Chemical Additives and Fillers
Authors: Lautenschlaeger F. K. , Edwards K.
Published: February 2011

The effect of chemical additives and fillers on the yield and distribution of sulfidic products in model compound vulcanization (MCV) reactions was studied. Several controversial issues were resolved, and a better understanding of the effect of chemical additives on the physical properties of natural rubber vulcanizates has resulted. Additives considered as radical scavengers can increase or decrease the yield of products which correspond to crosslinks. The effect of peroxide depends on the type of accelerator; it is significant with thiuram disulfide acceleration, but negligible with sulfenamide acceleration. The product distribution from an organic dialkyl tetra-sulfide as a sulfur donor is shown. An inorganic disulfide, such as molybdenum disulfide, does not take part in the sulfur vulcanization. An analysis of the effect of fillers on the yield and distribution of those sulfidic products which correspond to crosslinks, and on the sulfidic byproducts was carried out. A similar detailed analysis cannot be achieved in vulcanizates. It was shown that the yield and distribution are significantly affected by inorganic and mineral fillers. MCV was applied to the analysis of the effect of silane coupling agents. Their beneficial effect on the yield and distribution of sulfidic products was shown. The yield of sulfidic byproducts is highest with fumed silica. An equivalent state of cure in filler-containing model vulcanizates should be established by accelerator activator and sulfur variations prior to the evaluation of fillers in the vulcanizates. This would enable a more direct evaluation of fillers, since their chemical and physical effects on the vulcanizate properties would be separable.
Interaction of Silica with Functionalized SBR
Authors: Edwards D. C. , Sato Kyosaku
Published: February 2011

In the absence of chemical interaction between precipitated silica and styrene-butadiene rubber, reticulation of silica particles occurs in the unvulcanized mixture and produces a stiffening effect. This process occurs gradually at room temperature and very rapidly at curing temperatures. The effect can be quantified conveniently by measuring the Young's modulus of raw compounds. SBR functionalized with a small concentration of hydroxyl groups, introduced by terpolymerization, can interact with precipitated silica particles by esterification. This reaction can be accelerated by catalysts. When carried out under conditions of combined heat and shear, this interaction prevents silica reticulation and produces vulcanizates with greatly altered and improved elastic properties. The present paper describes and illustrates these effects with reference to simplified compound recipes.
Low Temperature Dynamic Properties of Bitumin-Rubber Mixtures
Authors: Shim-Ton J. , Kennedy K. A. , Piggott M. R. , Woodhams R. T.
Published: February 2011

The influence of four different elastomeric materials on the low temperature dynamic properties of bitumen was determined using a Rheovibron Viscoelastometer. The four elastomeric materials included two waste products and two liquid rubbers : powdered vulcanized tire reclaim rubber, precipitated waste SBR latex from an effluent recovery system, liquid carboxy-terminated butadiene-co-acrylonitrile polymer (Goodrich CTBN), and liquid polybutadiene with terminal allylic bromine substituents (Polysar Liquid RTV Polymer). The results of the evaluation indicate that liquid polybutadiene is the most efficient low temperature flexibilizer, as might be expected from its low second order transition temperature (−85°C). A comparison of the penetration of the rubber-bitumen mixtures with the Brookfield viscosity reveals that the addition of rubber markedly reduces the temperature susceptibility. Attempts were also made to follow the thickening behavior of bitumen/ CTBN rubber mixtures after the addition of calcium hydroxide. The large increase in viscosity immediately following the addition of calcium hydroxide was followed by a gradual return to a slightly lower viscosity than the original bitumen-rubber mixture. The implications of the low temperature dynamic transitions, viscosity behavior, penetration values and thickening behavior of bitumen/rubber mixtures with respect to road performance are discussed.
Bromine Terminated Liquid Polybutadiene as a Solventless, Room-Temperature Adhesive System
Authors: Koshute M. A. , Stephens H. L.
Published: February 2011

This study involved the determination of the work of adhesion (Wa) to separate neoprene rubber from structural steel, using different formulations of room temperature cured dibromobutadiene (DBBD) as the adhesive system. The Wa of both the metal-to-adhesive (M-A) and rubber-to-adhesive (R-A) interface was determined by 180° peel tests at constant rate and temperature. The results of this investigation have shown that the level of adhesion can be controlled through the formulation of DBBD with different ratios of the curing agent MPEHA. The work of adhesion was found to increase with increasing crosslink density, but eventually reached a maximum value at an optimum crosslink density or molecular weight between crosslinks. Formulations containing an optimum level of the accelerator lead dimethyl-dithiocarbamate (Ledate) and organosilane coupling agent Z-6032 had a synergistic effect on the system. This optimum formulation was cured in 3 days and yielded values of Wa for the R-A interface equivalent to the 7-day cured optimum system of DBBD/MPEHA containing no additives, and increased the value of Wa for the M-A interface. The work of adhesion for the optimum system was found to increase with adhesive layer thickness, but obtained a maximum value at an optimum thickness. Cyclization was determined to be the best treatment of the neoprene surface to increase the Wa at the R-A interface. Testing of the optimum adhesive system at temperatures significantly lower than room temperature showed an increase in Wa at the R-A interface but no change at the M-A interface. However, testing at temperatures significantly higher than ambient yielded lower Wa values at both interfaces. The work of adhesion of the optimum adhesive system dropped significantly after 22 hours of water immersion. Further work should be carried out to increase the work life of the formulated adhesive and the hydrolytic stability of the total system.
Thermal Expansion Phenomena in Filled and Unfilled Natural Rubber Vulcanizates
Authors: Thiele J. L. , Cohen R. E.
Published: February 2011

As with polybutadiene and SBR compounds, filled and unfilled vulcanizates of natural rubber exhibit long transients in their linear thermal expansion response following sudden changes in temperature. This is particularly noticeable when the materials are prestretched well beyond the point of thermoelastic inversion. Incorporation of 50 phr of carbon black significantly reduces the magnitude of the linear thermal expansion coefficient for natural rubber compounds; this reduction is greater than expected on the basis of comparisons with previous data on filled SBR vulcanizates. Changes in the surface chemistry of the filler have little effect on the thermal expansion behavior. For the unfilled vulcanizate, an equation based on rubber elasticity theory was successful in predicting the strain dependence of the linear thermal expansion coefficient up to moderate levels of strain. At higher strains the large deviations from theory were observed.
Scanning Electron Microscopy Studies of Nitrile Rubber Fractured Surfaces
Authors: Bhowmick A. K. , Basu S. , De S. K.
Published: February 2011

The fracture surfaces of a NBR vulcanizate after different test conditions have been studied by scanning electron microscopy. It has been shown that failure surfaces manifest typical characteristics dependent on the nature of the test. Tensile fracture surface shows occurrence of two different tear rates in the case of a filled NBR vulcanizate, while tear fracture is characterized by a few long flow lines. De Mattia flexing leads to layering of polymer fibers. Heat buildup and abrasion tests generate a ribbed structure on the surface.
Improved Service Life of Automotive Suspension Bushings through the Use of Semi-Efficient Vulcanization Systems
Authors: Paris W. W. , Doney C.
Published: February 2011

The relative merits of antiozonants, efficient vulcanization systems, and semi-efficient vulcanization systems for natural rubber in dynamic applications have been previously evaluated in a number of laboratory studies. This report covers an evaluation of the effects of these three factors on the laboratory fatigue testing of automotive suspension bushings. The use of semi-efficient vulcanization systems along with a good soluble antioxidant will provide the optimum resistance to the combined effects of oxidation and mechanical fatigue experienced in this application. Efficient vulcanization systems produce products with very poor service life. The use of substituted p-phenylenediamine (ppd) antiozonants can be an advantage or disadvantage in compression fit bushings, depending upon the type of service. Excessive amounts of ppd at the rubber-to-metal interface can cause slippage and early failure; therefore, the use of ppd's must be approached with caution in this application.
Rubber Mixing
Authors: Funt J. M.
Published: February 2011

Model studies on particle dispersion have led to insights which have increased understanding of the mixing process. Despite the complex flows which arise in practical mixing equipment, model calculations have highlighted the essential flow patterns which occur and have guided understanding of the application and limits of use of practical techniques such as power integrators. Using these tools, process engineers have realized substantial savings in energy usage and mixing time, while maintaining or improving mix quality.
Reactions of Resin Formers in Dry Bonding Rubber Systems
Authors: Morita E.
Published: February 2011

An unusual two step viscosity change was observed during the Mooney scorch test of some dry bonding stocks of a NR/SBR blend. This behavior was found to involve the resin formation and resin crosslinking of rubber. The effects of the resin formers, hexamethylenetetramine as the methylene donor and resorcinol, m-aminophenol or m-phenylenediamine as the acceptor, were analyzed by the application of a prevulcanization inhibitor. The merits of m-phenylenediamine as an adhesion promoter are described.
A Non-Linear Viscoelastic Characterization of a Natural Rubber Gum Vulcanizate
Authors: Sullivan J. L. , Morman K. N. , Pett R. A.
Published: February 2011

The utility of the generalized strain measure viscoelastic equation (the CBT theory) has been demonstrated in part by excellent agreement of experiment with pure shear predictions calculated from simple tension results. Similar successes employing the generalized strain measure have been reported elsewhere. FLV predictions also demonstrated good correlation by matching predictions based on the CBT theory. However, in order to avoid excessive sensitivity to experimental error, regression parameters appearing in the FLV theory, especially for the “third order” form, were evaluated from data first smoothed using the CBT tensile elastic equation. In the future, we expect the “third order ” form to be useful at large deformations where more regression constants are needed to adequately characterize a broad deformational domain. Predictions of the storage modulus in simple tension based on either the FLV or the CBT theory agree with experiment to within approximately 10% error. Although this error is considered good from an engineering point of view, efforts are underway to identify its origin and to reduce its magnitude. Loss modulus predictions of either theory are only in semi-quantitative agreement with experiment. The frequency response of experimental E2 values is matched reasonably well by theory, but the deformational dependence of the data is lost due to relatively large scatter.
Contribution to the Mathematical Description of Stress-Strain Behavior of Elastomers
Authors: Tobisch K.
Published: February 2011

Based on the hypothesis of Valanis and Landel that the strain energy density function W(λx,λy,λz)could be represented as the sum of three identical functions ω(λi) of the principal extension ratios λi(i=x,y,z), an expression for ω(λi) is suggested which is distinguished by its relative simplicity. The stress-strain relations developed from this expression are tested successfully by applying them to experimental results of other authors. The types of strain which were examined were simple extension, biaxial extension and pure shear; the elongations were to about 700%.
Computation of Stresses, Strains, and Deformations of Tires
Authors: Ridha R. A.
Published: February 2011

The pneumatic tire is often taken for granted as a simple and reliable component of the vehicle. A closer look, however, shows that the tire in service is subjected to severe stresses and deformations whose quantities must be determined in order to accurately predict tire performance. Modern tire structures have evolved through a series of modifications of the original pneumatic rubber tire. These modifications were based on field experiences and on mostly experimental studies of tire behavior. The use of analytical techniques to calculate tire stresses and deformations remained limited in scope for a long time because the complexity of the tire structure placed it beyond the domain of available methods of analysis. The recent emphasis on analytical techniques is due, at least partly, to their potential for becoming less time consuming and less expensive than experimental methods, the need for predicting a tire's behavior before its manufacture, and the notable advances in computational and structural analysis methods. In this paper, these methods are described and applied to the calculation of tire stresses and deformations. Structural analysis is the analytical determination of structural responses to a prescribed set of applied loads. The responses may be displacements or distortions if force loads are known, or forces if displacement or distortions are known. Given the geometry of a structure (shape, dimensions), the relevant properties of its component materials, the magnitude and distribution of applied loads, and any constraints from boundary conditions, then structural analysis is used to calculate displacements, strains, or stresses at any chosen location in or on the structure. These calculated values may be compared to those required for functionality of the structure. Although structural analysis is not directly applicable to determining the most efficient configuration of the structural components, the analysis of successive well chosen modifications can often optimize compositions or geometries. The application of structural analysis to a tire requires (a) knowledge of the relevant physical properties of the component materials, and their configuration in the tire, (b) complete characterization of the applied loads, and (c) an analytical technique (i.e. theory) for calculating the required responses. These requirements are explained in the following sections.
Factors Affecting Cord-to-Rubber Adhesion by a Tire Cord Adhesion Test
Authors: Fielding-Russell G. S. , Livingston D. I. , Nicholson D. W.
Published: February 2011

The physical factors affecting the force required to pull a cord from the cord-rubber specimen used in a new tire cord adhesion test (TCAT) were investigated using a variety of rubber compounds, specimen cross-sectional areas, and tire cords. Below a limiting cross-sectional dimension, the cord pull-out force was proportional to the square root of cord perimeter, specimen cross-sectional area, and Young's modulus of the rubber, as anticipated from theoretical considerations. The constant of proportionality involved the square root of the energy of adhesion. The value of the energy of adhesion calculated from the proportionality constant was confirmed by an independent peel test.
An NMR Investigation of the Interaction between Carbon Black and Cis-Polyisoprene
Authors: Svensson L. G. , Svanson S. E.
Published: February 2011

Attempts have been made to change the methods of preparation of samples of IR filled with various carbon blacks. Considering experiments where reliable results have been obtained hitherto we have drawn the following conclusions: 1. For solution-mixed and short-milled samples, a large broadening is observed, which is reduced by extraction, heating the samples above 50°C, and by prolonged milling. It is assumed that this broadening is due to interactions of a physical nature. The remaining broadening effect is assigned to irreversible effects of a chemical nature. 2. For dry-milled samples, where prolonged milling is always needed to achieve reasonable mixing, the main part of the broadening effects is not changed by the above treatments. 3. By heating the products to temperatures above 180°C a pronounced broadening develops. We believe that the largest surface interaction is attained by this treatment.
Kinetics of Crosslinking and Network Changes in Natural Rubber Vulcanizates with a Dithiodimorpholine Based Accelerator System
Authors: Bhowmick A. K. , De S. K.
Published: February 2011

Kinetics of crosslinking and network changes in unfilled and filled natural rubber vulcanizates with a dithiodimorpholine based accelerator system have been studied at 150° and 180°C. Results show that addition of HAF black enhances the polysulfidic crosslinks as well as the total crosslinks. This has been explained with the help of Coran's model wherein HAK black increases the rate constants. It is likely that the filler surface prevents desulfuration and undesirable side reactions involving the crosslink precursors. Increase of curing temperature by 30°C lowers the total crosslink density and increases the sulfur inefficiency.
A New Investigation of Tetrahydrofuran-Based Polyether Glycols in Urethane Elastomers
Authors: Pechhold E. , Pruckmayr G. , Robinson I. M.
Published: February 2011

Random copolyether glycols with 50 mole % EO and low cyclic ether content represent novel soft segments for polyurethanes, and have some advantages over the other soft segments as shown in Table V. THF/EO copolyether glycols are easier to handle and to process because they are liquids at room temperature and exhibit lower viscosities and better diol compatibility. Physical properties of polyurethanes made from THF/EO copolyether glycols are comparable to those made from other soft segments; the hydrolytic stability and low temperature behavior are superior to polyester and polycaprolactone glycols, and solvent/oil resistance is better than PTMEG. THF/EO copolyether glycol is a replacement for PTMEG only with reformulation; it could be considered for applications which require better solvent/oil resistance or easier handling and processability.
Elongational Flow in Mixing Elastomer with Carbon Black
Authors: Nakajima N.
Published: February 2011

The mechanism of mixing elastomers with carbon black involves elongational as well as shear deformation. Therefore, elongational measurements on raw elastomers and compounds are important in understanding the processing behavior. In this paper, the definition of elongational flow is discussed, its application to the mixing equipment is examined, and some results from elongational measurements with raw elastomers and a carbon-black-containing compound are presented.