bluuebunny/crossref_metadata_2025 huggingface dataset:
Vulcanization of Elastomers. 36. Vulcanization of Natural Rubber and Synthetic Rubbers with Sulfur in Absence of Accelerators. II
Authors: Scheele W. , Müller H. , Schulze W.
Published: February 2011

In continuation of earlier work with natural rubber, the kinetics of sulfur decrease were studied in certain synthetic rubbers for different temperatures and sulfur concentrations. At the same time the formation of polysulfide bound sulfur was studied, using as example the reaction of sulfur with natural rubber and synthetic rubbers. It was found that: 1) When the decrease in sulfur concentration is portrayed by curves which are convex to the time axis (Perbunan), the 0.6th order time-law is fulfilled, (as in the case of natural rubber independent of temperature and concentration. 2) In contrast, the concentration dependence of the rate at which sulfur decreases, both in Perbunan and cis 1,4-polybutadiene, denotes a first-order reaction in agreement with experience with natural rubber. 3) The activation energy of sulfur decrease has the same magnitude for all the elastomers investigated (34 to 36 kcal/mole). 4) The disagreement between the time law and the concentration dependence of the rate of sulfur disappearance encountered in all the experiments with 1,5-polyenes, is interpreted as indicating autocatalysis, which likewise explains the shape of the curves for sulfur disappearance. 5) Sulfur reacts considerably faster in natural rubber and Perbunan than in cis 1,4-polybutadiene; consequently a homolytic dissociation of the S8-ring cannot be rate-determining. 6) Polysulfide sulfur shows, in each case, a maximum with reaction time, and in completely reacted vulcanizates it tends toward a limiting value. An equation was found, which provides a good description of change with time of polysulfide concentration (natural rubber and cis 1,4-polybutadiene). 7) An explanation is given for the appearance of the polysulfide maximum; and how the reaction of sulfur with 1,5-polyenes can be represented, making use of all available results, is discussed.
Characterization of Polymer Decomposition in an Inert Atmosphere by Thermogravimetry
Authors: Smith D. A.
Published: February 2011

The paper reports weight loss vs temperature data for the pyrolytic decomposition of polyethylene, Polyvinylchloride; natural, styrene-butadiene and isopreneisobutene rubbers. A nonisothermal kinetic treatment is developed, based on proposals by Doyle and by Newkirk, resulting in characterization of the pyrolysis by two principal parameters, the “integral procedural decomposition temperature” (Tp) and the “procedural activation energy” (Ep). The effects of environmental variables are discussed and it is concluded that Ep is insensitive to detailed procedural variation but appears to reflect differences in stability between polymers. For a number of polymers, the values obtained agree well with values from isothermal measurements reported in the literature. An indication is given of how the method may be used to assess rapidly the effects of compounding on the pyrolytic stability of polymers.
Transmissibility through and Wave Effects in Rubber
Authors: Payne A. R.
Published: February 2011

Instruments and precision machine tools are now being used in increasing quantities, and often in places which are subjected to severe vibration environments. Precise and costly electronic equipment in aircraft and missiles are currently subjected to severe vibration hazards. Increasing use is now being made of intentionally produced vibrations for such purposes as a drive for a mixing sieve, for conveying, for mold shaking and for vibration and shock testing. All these environmental situations demand the development of suitable and effective vibration isolation devices. Unhappily, adequate vibration isolation is not merely a matter of interposing any kind of rubber or metal springing, because the incorrect use of such elastic materials may actually make matters worse. Our understanding of the requirements for the best type of rubber, or rubber compounding is limited and only of recent origin, but it is the purpose of this review to discuss the problems of vibration isolation and insulation, not from the point of view of mechanical vibration theory alone, but to discuss how these theories can help to decide what properties are required of the rubbers to obtain maximum protection. It is not intended to discuss the actual design of antivibration shock mountings and couplings as these have been surveyed in recent publications.
Carbon Black-Rubber Interactions and Bound Rubber
Authors: Stickney P. B. , Falb R. D.
Published: February 2011

The interaction of elastomers with fine particles has been a subject of great interest and much controversy for many years. This is easy to understand when it is remembered that reinforcement is one of the three great developments that underlie the extensive use of elastomers in our modern world. The other two are, of course the discovery of the principle of vulcanization, and the development of synthetic elastomers, including many having special properties superior to those of natural rubber. A large part of the controversy currently includes specifically the question of the special position—or lack of it—of carbon black as a particulate filler for elastomers. The resolution of this question is beyond the scope of our present knowledge, although strong opinions are held on both sides of the question. However, for two reasons, the present review will be restricted almost entirely to a consideration of the nature of the interaction of carbon black with hydrocarbon elastomers. The first reason for this is the undeniable technological importance of these systems. The second is the relatively small amount of work that has been reported on other types of fillers. In addition, the inclusion of other fillers would certainly add to the complexity of any attempt to analyze polymer-filler interactions at this time. However, it must be admitted that the possibility exists of explaining all polymer-filler interactions ultimately in similar and relatively nonspecific terms. In the past few years, an enormous amount of work has been reported that has a bearing on this problem. From the results of these investigations, a coherent explanation appears to be emerging. This paper attempts to review some of the more important work in this field in order to present an over-all picture of our present knowledge. The problem can be summarized in three questions:
A Review of Cord-Rubber Elastic Characteristics
Authors: Clark Samuel K.
Published: February 2011

The increased use of cord- and filament-reinforced materials in structural applications during the last few years has resulted in a greater interest in their elastic properties. In part the reason for this may be found by considering the basic nature of redundant structures, in which the loads carried by individual cords are determined to some extent by the elastic characteristics of the entire system. In such situations, a knowledge of elastic characteristics becomes important to structural design practice. As a second reason for increased attention to the elastic properties of such materials, one might cite the body of work which is now developing in the general area of filamentary reinforcement of materials. A knowledge of elastic characteristics is important in obtaining optimum reinforcement properties, and such studies inevitably lead to a clearer understanding of the internal stress-states of all reinforced materials. One result of all this activity is that much of the work done in the areas of fiberglass and whisker reinforcement increases the general understanding, in a broad way, of the action of cord-reinforced rubber since in many respects the problems are similar, although major differences do exist in the structure of the reinforcement itself. The elastic properties of cord-rubber materials are understood today much better than they were even ten or fifteen years ago. A great deal of this development has paralleled, and is well represented by, internal stress analysis techniques developed for what is perhaps the primary utilization of cord-reinforced rubber, namely, the pneumatic tire. In the case of the pneumatic tire, these stress analysis techniques have essentially followed three distinct phases. In the first, the anisotropic nature of such materials was completely ignored and loads and stresses were determined on the basis of assuming the materials to be isotropic or unreinforced. In the case of shell structures, this is the equivalent of calculating the statically determinate membrane stresses. In some cases such information was valuable and in a few instances it comprised a major portion of the effects being studied so that some reliance could be placed on such an analysis. However, in general, due to the complex nature of such reinforced materials, little faith can be given to analyses based on isotropic conditions.
Observations on the Crosslinking of Natural Rubber with Nitrosophenols and Diisocyanates
Authors: Lautenschlaeger F. K. , Myhre M.
Published: February 2011

1. The vulcanization system based on nitrosophenols (quinone monoximes) is not primarily based on the formation of a urethane group. Evidence is presented that the crosslink consists of carbon—carbon, carbon—sulfur, and urea groups. Urea groups can be identified in reaction products which also contain the free phenol group of the nitrosophenol (oxime); urethane groups are identified in products which also contain quinone groups. 2. The presence of zinc dithiocarbamate is conducive to the formation of the amino group which is the functional group on which the crosslinking reaction with diisocyanate is based. The dithiocarbamate also acts as a sulfur donor. The dialkyl amino group of the dithiocarbamate is bound into the network. 3. Nitroso compounds which have no tautomeric oxime structures show no vulcanization in combination with free diisocyanate. 4. The level of vulcanization of various substituted phenols, when used in combination with a diisocyanate precursor, is dependent on their thermal decomposition termperatures, but such a dependence is not apparent when these compounds are used in combination with free diisocyanate. 5. A reaction mechanism is suggested for the vulcanization with oximes and diisocyanates which does not require the splitting of their adducts into their components but instead into ionic fragments. This mechanism explains why monoximes lead to vulcanization whereas nitroso compounds do not. 6. Attempts to effect premature vulcanization should be directed towards delaying the formation of the diisocyanate/oxime adduct since it provides the vulcanization-active intermediates. Towards this goal it has been shown that a diisocyanate precursor can be applied but then a thermally stable nitroso compound (oxime) is required. 7. Tautomerism between O-derivatives of oximes, nitrones, and oxaziridines can be assumed to provide a working hypothesis for the discovery of new N-O-containing crosslinking agents for unsaturated polymers.
Variations in Tire Hysteretic Losses Due to Tire Design
Authors: Willett P. R.
Published: February 2011

The technique of analyzing energy losses of tires that have reached a state of thermal equilibrium has been applied to cross-ply and radial-ply passenger car tires and cross-ply truck tires. The derived formulations relating the tire energy losses to the viscoelastic properties of the tire components show the dependence of these losses on tire size and construction. The analysis was carried out by systematically varying tire tread compounds and operating parameters. This investigation of the energy losses experienced by tires operating in a state of thermal equilibrium, has enabled the losses due to the various stress-strain deformations to be characterized. In particular, the losses due to the strain deformation have been correlated with two mechanisms, which are outlined. The results described enable a better understanding of the mechanisms responsible for tire energy losses and allow the tire losses to be predicted at the design stage.
Mobility of Extender Oil in Tires under Service Conditions. I
Authors: Deviney M. L. , Whittington L. E. , Good C. W. , Sperley R. J.
Published: February 2011

This study has been conducted to correlate the extent of oil diffusion in tires during service with the resulting effects of oil migration on the compound properties as they relate to tire performance.
The Effects of Oil on Adhesion of Rubber
Authors: Beatty J. R.
Published: February 2011

It has been shown for poly(isoprene) rubber, both natural and synthetic, that the usual processing oils have essentially no effect on adhesion. The materials to which this statement apply are brass-plated wire, brass metal, steel, and R.F.L. dipped rayon, nylon, and polyester. The modulus of the rubber compound must be maintained constant by addition of carbon black to obtain these results. This work opens a new approach to the compounding of rubber compounds where good adhesion is necessary. It provides improved processing and reduced cost with no detrimental effect on adhesion properties.
Viscoelastic Properties of Polyurethane Block Polymers
Authors: Seymour R. W. , Cooper S. L.
Published: February 2011

Orientation measurements using differential infrared dichroism experiments have been applied to the study of the viscoelastic properties of polyurethane block polymers. The time dependence of the orientation function reflects the influence of both the viscoelastic nature of the blocks and of the two-phase microstructure. A study of the effect of hard block length on the orientation response suggests the presence of an interlocked hard phase structure for most compositions. Such a structure severely restricts relaxation of orientation under strain. At very short hard segment lengths, this morphology is not present and extensive relaxation does occur.
Dependence of Laboratory Tire Cord Adhesion on Rubber Properties
Authors: Erickson D. E.
Published: February 2011

H- and strip adhesion results on nylon and glass tire cords were found to depend on various physical properties of the adhering rubber compounds. The strip adhesion test was most affected by changes in tensile strength and elongation, with higher values of adhesion being measured with high elongation-high strength compounds. Tensile strength was especially influential in the case of hot strip adhesion. H-adhcsion results were more affected by the characteristics of the rubber during curing than by the tensile properties of the cured rubbers. Compounds having higher Mooney viscosities developed higher pressures in the curing mold. Because of this tendency, the rubber was postulated to penetrate more thoroughly into the tire cord, giving better mechanical and physical bonding because of the better contact. Rubbers which were slower curing, as indicated by long optimum cure times, tended to increase H-adhesion, presumably because they allowed better interfacial bonding by their capability for increased curative or polymer diffusion before complete self-curing of the rubber. High Mooney viscosities and long optimum cure time were particularly effective in increasing H-adhesion of glass cord because of the normally low level of mechanical bonding of the rubber to glass cord (because of its low twist). Nylon cord, normally higher in mechanical bonding which results in overall higher levels of H-adhesion, was high in room temperature H-adhesion to high Mooney compounds. However, the tensile strength was controlling in the case of hot H-measurements of nylon cord because of the greater level of mechanical bonding already present. Room temperature and hot “tear ratings” representing the rubber coverages on delaminated strip adhesion samples varied with the optimum cure times of the rubber compounds rather than with tear strength. As in the H-adhesion samples, the lower-cure-rate rubbers are thought to increase the bonding between dip and rubber by increasing the diffusion of curatives or polymer segments at the rubber-to-dip interface. Hot “tear ratings” also showed an inverse correlation with tensile strengths, indicating that the hot strength of the rubber layer is low enough in some cases to make that intermediate layer the weakest point in the laminate, and strong enough in other cases to force the delamination to occur between the cord and rubber, giving low tear ratings. The delamination force measured in hot strip adhesion tests varied as the square of the tensile strength of the ply rubber, in agreement with Kaelble's theoretical expression. However, the peel force did not vary inversely with the 100 per cent rubber modulus, as predicted if that parameter is related to Young's modulus.
The Effect of Carbon Black Parameters on the Fatigue Life of Filled Rubber Compounds
Authors: Dizon E. S. , Hicks A. E. , Chirico V. E.
Published: February 2011

Fatigue is defined as decay caused by cyclic deformations at an amplitude less than necessary for fracture in one cycle. Such failures are initiated by flaws which act as stress concentrators. These flaws occur in the material either through mechanical or chemical action during service or through agglomeration of certain ingredients during mixing and fabrication. This paper deals with the latter process, where the nature and size of the flaws as well as the properties of the matrix are contingent on carbon black variables. Using the tearing energy concept of fatigue developed by Lake and Lindley, it was shown that the size of the flaw is primarily determined by carbon black particle size. On the other hand, the cut growth constant depends on carbon black structure. When translated to actual fatigue life using the Monsanto Fatigue-to-Failure Tester, these relationships mean that under constant strain conditions, compounds containing coarse carbons will have a significantly higher fatigue life than those with fine carbons. Under conditions of constant strain, higher structure carbons will impart a slight positive effect. However, under conditions of constant stress, the beneficial effects of structure become magnified. Other factors known to affect fatigue life were also considered. These are : set, stress relaxation, hysteretic energy dissipation, and flaw size distribution.
Effect of Heterogeneous Carbon Black Distribution on the Properties of Polymer Blends
Authors: Sircar A. K. , Lamond T. G. , Pinter P. E.
Published: February 2011

The results of this work support earlier findings regarding the transfer of carbon black in blends of BR with SBR, NR, and CIIR. Compared to conventionally-mixed compounds, in most cases vulcanizates with a heterogeneous carbon black distribution have superior hysteresis properties, presumably due to the presence of the unloaded layer mitigating the generally observed deleterious effects of carbon black upon these properties. The effect of unloaded SBR or BR layers on stress-strain values is quite small in SBR/BR blends where the zone size of the elastomer phases is small, but significant in SBR/NR and BR/NR where the zone size of the elastomer phases is larger. Superior cut growth resistance is seen for NR/BR and SBR/BR blends containing unloaded BR. The properties of SBR/BR and NR/BR blends in which most of the black is in the BR phase suggest that they may find utility in applications where superior hysteresis properties are required; e.g., in radial-tire sidewalls. Compounds with a heterogeneous carbon black distribution may also find utility in wire and cable applications, due to their superior insulating properties.
Elastomeric Polyblends—Structure-Property Relationships
Authors: Falender J. R. , Monroe C. M.
Published: February 2011

Specific preparative techniques have been used to synthesize polyblend structures showing interesting properties. Many structural variables remain to be investigated. Of particular interest for the near term future is the effect of altering interphase adhesion.
Preliminary Investigation of the Feasibility of Radiation Vulcanization of Silicone Rubber
Authors: Przybyla R. L.
Published: February 2011

Radiation vulcanization of silicone rubber is commercially feasible from the standpoint of obtaining useful physical properties at relatively low dosage rates. These physical properties are approximately equivalent to those obtained by peroxide vulcanization. We found that, for the limited number of samples tested; the electrical properties, the confined heat resistance, the compression set resistance, and the heat aging were all equivalent to their peroxide counterparts.
The Synthesis and Spectral Characteristics of Some Nitrosoanilines and Their Possible Mode of Action as Curing Agents for Various Types of Rubbers
Authors: Potts K. T. , Kane J. , McKeough D. , D'Amico J. J.
Published: February 2011

Spectral characteristics of several known and new N-substituted-p-nitrosoanilines, e.g., Nitrol, of established utility in promoting the bonding between rubber and carbon black are described. A possible mode of action in their enhancement of the bonding process involving a classical free radical process is discussed.
Deformational Behavior of Rubber in a Variable Speed “Mooney” Rheometer
Authors: Nakajima N. , Collins E. A.
Published: February 2011

Because the Mooney Rheometer is widely used and accepted in the laboratory and the plant a closer examination of what it measures is warranted. Although the steady torque value has been converted to steady-state viscosity, the “Mooney torque—time curve” has not been reduced to fundamental parameters. This work, carried out with SBR 1500, treats the initial torque rise as the shear stress-strain behavior analogous to tensile stress-strain. A master curve was constructed from such data obtained at various speeds using a principle of corresponding states. The master curve closely resembles the steady-state viscosity curve and at high shear rates joins the complex viscosity curve measured with the Rheovibron. In addition the use of the transient data enables one to extend the low shear end of the viscosity-rate curve by two decades. The peaks of the torque—time curves strongly suggest that they represent failure points of the material.
Molecular Structure and Macroscopic Properties of Synthetic Cis-Poly(Isoprene)
Authors: Grechanovskii V. A. , Poddubnyi I. Ya , Ivanova L. S.
Published: February 2011

By changing the sol-gel ratio and the structure of the gel fraction it is possible to obtain various grades of synthetic cis-poly(isoprene) which show promise for different applications in the tire and mechanical rubber goods industries. The processability of commercial SKI-3 rubber (at a given average molecular weight of sol) depends mainly on the structure of the gel fraction. Thus, for example, inferior processing properties of rubber compounds is associated primarily with the presence of tight gel. The content and structure of the gel fraction also significantly affect plasto-elastic properties of raw rubbers, e.g. a low plasticity of raw rubbers owes to the increased content of gel fraction. The reduced green strength of compounds based on SKI—3 rubber is accounted for by its chemical structure. Conventional methods used to change the properties of rubbers (including the variation in molecular weight, molecular weight distribution, branching degree, and variation in the content and structure of gel fraction) cannot be considered to be adequate to tackle the problem of the green strength of SKI—3 black stocks. The way to solve the problem appears to be the introduction of functional groups into the polymer chain at the stage of synthesis or processing. These functional groups should be active as to the formation of labile rubber—carbon black—rubber and/or rubber—rubber bonds. High purity of microstructure is necessary but not sufficient for obtaining the required level of green strength of compounded SKI—3. The gel fractions of SKI—3 rubber yield vulcanizates with a more dense network than the corresponding sol vulcanizates. The temperature dependence of the tensile strength is controlled by the network density of vulcanizates from high cis-1,4 poly(isoprene).
Study of Orientational Transformations of Supramolecular Structures on the Surfaces of Uniaxially Stretched Elastomers
Authors: Nel'son K. V. , Tkachenko G. T. , Ionina N. V.
Published: February 2011

Characteristics of surface orientation of cis poly(butadiene) elastomers with covalent crosslinks were studied with data from MPTIR ir spectroscopy and electron microscopy. It was shown that the supramolecular structures observed in electron photomicrographs of uniaxially stretched elastomer surfaces and their spatial reorganization correlate completely with changes in dichroism of a series of absorption bands in the MPTIR ir spectra. It was established that the maximal dichroism values in the MPTIR spectra correspond to orientation of coarse fibrillar forms, and the subsequent dichroism decline, corresponds to their deorientation. It was shown that, according to the extent of deorientation of the coarse fibrils, an increase in the cross section of the thin fibrils occurs with sharper margins separating them from the disordered part of the polymer; it was established by this that in the MPTIR spectra Rxy is partly increased, the intensity of a series of vibrations grows, and new absorption bands appear. The indicated facts are explained as due to intrafibrillar crystallization.
Heat Generation in Tires Due to the Viscoelastic Properties of Elastomeric Components
Authors: Willett P. R.
Published: February 2011

The relationship between the heat generation as experienced in the tire shoulder and the viscoelastic properties of the tire elastomeric components has been formulated. The analysis was facilitated by adopting the technique of multiple regression where the significance of each response equation was statistically evaluated. The physical intepretation and consequences of such response equations have been extensively discussed, whereas literature on the subject is incomplete. Effects of tire construction and size on the heat generation in the shoulder region was carried out by analyzing the results of tires that had reached a state of thermal equilibrium on an indoor tire-dynamometer. The tires used in the analysis were cross-ply and radial-ply passenger tires and cross-ply truck tires. Within the limits of such an analysis, the heat generation experienced in the tire shoulder was predominantly due to the condition classified as that of constant stress amplitude.
Short-Fiber—Rubber Composites: The Properties of Oriented Cellulose-Fiber—Elastomer Composites
Authors: Coran A. Y. , Boustany K. , Hamed P.
Published: February 2011

Unregenerated-cellulose-fiber-elastomer composites with widely varying properties can be obtained. The properties depend on the type of elastomer used as the matrix, the fiber concentration, fiber aspect ratio, and fiber orientation. The fibers must be bonded to the matrix elastomer to obtain good strength. Composites of good strength can be prepared from a wide variety of elastomers. Composites with Young's modulus from 20000 to over 100000 psi and strengths up to 6000 psi can be obtained by varying the amounts or lengths of fibers. In addition, these compositions offer a high degree of dimensional stability; they resist creep deformation and solvent swelling. Further, compositions of good fatigue life under high stress conditions can be obtained. It is expected that the new composite compositions will find uses where good long-term load-bearing characteristics and dimensional stability are required. Uses in a number of environments are indicated since a wide variety of elastomers can be used as matrix.
Cord—Rubber Adhesion. A Quantitative Shear—Adhesion Test
Authors: Skolnik L.
Published: February 2011

Three independent proofs have shown that the slightly modified “H” pull-out adhesion test is in fact a quantitative measure of the shear adhesion strength of the system. Some examples of the usefulness of this quantitative shear-adhesion test have been described. The use of the principles of the test for dynamic adhesion testing of products, such as tires, was also described.
Elastomer Blends
Authors: Corish P. J. , Powell B. D. W.
Published: February 2011

Mixtures are difficult to define within the range of materials employed in the rubber and plastic industries. A composite article such as a tire is a mixture of wire (metal), textile cord (organic fiber), and rubber compounds. The rubber compound itself is a mixture of elastomer, filler, and, usually, extender. Moreover, the elastomer may be a mixture of two or more rubbers. On a smaller scale, the elastomer may contain ‘blocky’ segments or crystalline portions along the polymer chains which act as ‘reinforcing’ agents or stiffeners. These may be similar to the repeat units of the elastomeric part, e.g., isotactic—atactic block copolymers of poly(propylene) or poly(propylene oxide); or different from it, as in the stereo block styrene—butadiene thermoplastic copolymers. Two types of elastomer may of course, be copolymerized or one elastomeric type may be grafted onto another. Furthermore, certain catalysts could cause simultaneous homopolymerization of two monomers. All the foregoing systems are different facets of the broad concept of blends, but some selection is obviously needed. In this review, most emphasis will be placed on elastomer—elastomer blends including their preparation from the constituent elastomers. Reference will be made to elastomer—plastic blends prepared from separate materials and by block/graft type reactions. Blends of one plastic with another lie outside the scope of this review.
Scrap Tire Disposal
Authors: Beckman J. A. , Crane G. , Kay E. L. , Laman J. R.
Published: February 2011

Our overall objective in presenting this review is to call attention to the very complicated nature of the entire disposal problem. The whole field of scrap-tire disposal is full of alternatives, compromises, legislation, and conflicting reports on technological success. We will present a brief historical section explaining why the disposal of scrap-tires is now a problem (challenge) and the events that lead to it. Statistics on the annual volume of scrap-rubber generated and the volume disposed of by major processes will be reviewed. Existing and proposed legislation will be presented, and the probable impact on the rubber industry discussed. We will state what we believe to be the characteristics of an ideal solution. The technical aspects of scrap-tire disposal will not be neglected. The physical, thermal, and chemical values of a scrap-tire will be presented as a basis of defining potential uses for scrap-tires. The existing and proposed uses of scrap-tires as well as processes for disposal are extremely varied. We have decided to discuss processes for scrap-tire disposal under three general categories: physical applications, recovery of fuel value, and chemical processes. Certainly there are processes which overlap these artificial categories. We have concentrated on literature published in the last five years as a means of updating the reader. Private communications are liberally referred to in our review simply because this is the only way some information is available. We have also concentrated on large-volume uses or processes which have the potential for large volume. These uses or processes may be an immediate solution. However, we have also endeavored to record or comment on all ideas for scrap-tire disposal. Finally, we have expressed our opinion as to future trends.
Direct Analog Simulation of Hysteretic Heat Buildup in Rubber
Authors: Claxton W. E. , Conant F. S.
Published: February 2011

An instrument has been constructed for real-time analog simulation of temperature rise in a rubber article subjected to periodic strains. In an illustrative application to a tire tread; the effects of changes in ambient temperature, degree of internal cooling, addition of frictional heating and changes in distribution of hysteretic heat were studied. The results were in general agreement with experience on actual tires. Some suggestions are given for modifications to the instrument to increase its validity and versatility.
Adaptation of the Rheovibron to the Measurement of Dynamic Properties of Vulcanizates at Elongations up to Sample Rupture
Authors: Voet A. , Morawski J. C.
Published: February 2011

The Rheovibron dynamic tester can be adapted to the measurement of dynamic properties of elastomers at high deformations, up to sample rupture. The method used is superimposing small sinusoidal oscillations on statically extended specimen. In order to obtain significant dynamic data it is necessary to determine the value of Kc exactly, the correction factor for instrumental displacements, as well Kv, to correct for the deformation of the part of the specimen held within the clamps. It appears that Kv is dependent on amplitude, frequency, temperature, and sample characteristics and must be determined for each sample at each imposed condition separately. At higher extensions Kv corrections assume a major ro^le in the measurements, greatly complicating the procedures. The method for calculation of the correction factors advanced by Massa for glassy polymers does not hold for elastomers. A novel specimen arrangement has been developed, resulting in a zero Kv correction, independent of amplitude, frequency or temperature. With elastomers the Kc correction is generally also zero, leading to greatly simplified measurements as well as to more accurate results. The temperature control system of the Rheovibron was modified to permit specimen temperatures in the range of − 70° to +120° C, either at programmed increases or decreases or at any constant temperature in the range. The movement of the extension clamp was motorized, to ensure a regular, reproducible motion.
Variable Shear Rate Viscosity of SBR-Filler-Plasticizer Systems
Authors: Derringer G. C.
Published: February 2011

Variable shear rate viscosity studies of compositions with variable filler and plasticizer levels have led to the development of a unifying viscosity model. Application of the model indicated that the fillers studied are less effective as stiffeners at shear rates typical of factory processing operations than at the low shear rates characteristic of the Mooney viscosity test. Thus, for proper comparative evaluations of pigment effect on processing, Mooney measurements are inadequate. The effect of shear rate on plasticizer efficiency will require more work to make definitive statements. Plasticizer evaluations appear to be a fruitful avenue for further exploration. The model developed has proved useful in understanding the individual contribution to the viscosity of the compound by the raw elastomer, the filler, and the plasticizer over a wide range of shear rates. The availability of this model will also result in an economy of experimentation as each shear rate of interest need not be studied separately. Having a valid model makes it possible to optimize the experimental design with regard to cost and information.
Secondary Treatment of Wastewater from Synthetic Rubber Production
Authors: Troppe F. G.
Published: February 2011

Secondary treatment of wastes generated from synthetic rubber production was studied for a nine-month period. Its design criteria were flow of 3.55 MGPD and effluent reductions of BOD by 90 per cent and suspended solids by 95 per cent to 7 mg/l and 10 mg/l respectively. Average reductions of 84.2 per cent for BOD and 85.2 per cent for suspended solids were achieved. The treatment processes included neutralization, coagulation, flocculation, primary clarification, biological treatment, final clarification, and sludge impoundment. Dissolved air flotation aids clarification while aeration provides biological treatment. Raw wastewater was characterized by the presence of salt brine, dilute acid wastes, boiler blowdown, dilute latex, and coagulated rubber solids. Influent concentrations were BOD 72 mg/l, COD 447 mg/l, suspended solids 197 mg/l. Of the total project cost in excess of $2,000,000, approximately 25 per cent was utilized to segregate process wastewater from storm water. The average costs for operation, maintenance, and depreciation were $0.50 per 1,000 gallons of wastewater treated.
The Role of Certain Organic Sulfur Compounds as Preventive Antioxidants
Authors: Shelton J. Reid
Published: February 2011

The mechanism of autoxidation of organic materials by elemental oxygen is a free radical chain reaction initiated by hydroperoxide decomposition to form alkoxy and peroxy radicals. Chain scission and crosslinking reactions occur, along with the formation of hydroperoxide, resulting in degradation of properties of polymeric materials. The presence of unsaturation in natural and synthetic rubbers makes them particularly vulnerable to autoxidation, and antioxidants are thus essential to provide protection against oxidative degradation. There are two ways in which antioxidants can function to retard autoxidation. Preventive antioxidants act in some way to reduce the rate of initiation, while chain-breaking antioxidants intercept the chain-propagating peroxy free radicals and thus terminate the chain mechanism. Both types include a variety of compounds and possible modes of action as indicated in the following classification:
Importance of Singlet Oxygen in the Degradation of Rubbers and Plastics
Authors: Carlsson D. J. , Wiles D. M.
Published: February 2011

Singlet oxygen attack on rubbers and poly(olefins) is likely to be significant in the presence of sensitizing impurities such as oxidation products, polynuclear aromatic pollutants, and many additives. 1O2 attack will yield hydroperoxide groups, and so markedly impair the subsequent heat and light stability of the materials. However stabilizer systems which have already been developed can be expected to protect against the effects of 1O2 by quenching to the relatively inoccuous 2O3 (ground state oxygen). For rubbers the aromatic amines widely employed as antizonants will protect against 1O2 attack, whereas the nickel chelates employed as uv stabilizers will protect poly(olefins).
Oxidation of Poly(Isoprene)
Authors: Morand J. L.
Published: February 2011

A Prussian Blue colorimetric method has been developed to determine the number of conjugated polyenes present in commercial elastomers. These groups disappear at the onset of oxidation of unvulcanized lithium-poly (isoprene) : their content decreases by about 50 per cent during the first hour heating at 100° C in air. Simultaneously, a great number of volatile oxidation products are formed since the early stage of aging. The major products, the concentrations of which increase throughout heating until oxidation is advanced, are presumably produced by random attack on the regular isoprene units. The present investigation has made it possible to isolate from this group of compounds 4-methyl-4-vinyl-butyrolactone and 4-hydroxy-2-butanone, previously unrecognized, in addition to levulinaldehyde, methacrolein, and methyl vinyl ketone previously identified by Bevilacqua. An attempt was made to explain their origin. In addition to the compounds just mentioned, minor products corresponding essentially to unsaturated aldehydes and esters were also obtained. They might arise from the decomposition of conjugated polyenes which disappear at the start of oxidation. They have not yet been collected in sufficient amounts to confirm their structures and more experimental work is required to establish the mechanism by which they are formed.
Segmental Diffusion in Rubbers Studied by Neutron Quasielastic Incoherent Scattering
Authors: Allen Geoffrey , Higgins J. S. , Wright C. J.
Published: February 2011

Neutron scattering experiments on polymethylphenylsiloxane, poly(propylene oxide), poly(isobutylene), and poly(ethylene oxide) show broadening in the quasi-elastic region similar to that previously reported from polydimethylsiloxane. Measurements on partially deuterated samples confirm that the effect arises from segmental diffusive motion, rather than rotations of pendent side groups. The temperature dependence of this motion gives activation energies which are smaller than the activation energies for self-diffusion obtained from experiments of longer time-scale such as nuclear spin-lattice relaxation measurements and viscometry.
13C Nuclear Magnetic Resonance Spectroscopy of Polydienes, Micro Structure of Poly(Butadiene)
Authors: Clague A. D. H. , van Broekhoven J. A. M. , Blaauw L. P.
Published: February 2011

13C nmr spectra have been recorded of several poly(butadiene)s and their hydrogenated analogs, with various amounts of 1,2 structure, but with a roughly constant ratio of cis-1,4 to trans-1,4 structures. From an assignment of these spectra a detailed picture has emerged of the sequence distribution of the cis- and trans-1,4 and the 1,2 units in the poly (butadiene) chain. It is shown that these units are distributed in an essentially random manner and that 1,2 units are head to tail incorporated.
Non-Relaxing Crack Growth and Fatigue in a Non-Crystallizing Rubber
Authors: Lindley P. B.
Published: February 2011

The crack growth behavior of a non-crystallizing rubber, SBR, is investigated in terms of the tearing energy T, the energy available for crack growth. For cyclic deformations in which the minimum tearing energy is zero (relaxing conditions), a unique relationship is obtained between the growth per cycle and T at the maximum deformation. This rubber also exhibits crack growth at constant tearing energies. The relationship of the crack growth rate as a function of tearing energy, when the minimum tearing energy of the cycle is not zero, can be superimposed on the relaxing relationship by scaling the rates, and a tentative explanation is proposed for the scaling factor. Fatigue data are consistent with this.
Surface Friction and Dynamic Mechanical Properties of Polymers
Authors: Bueche A. M. , Flom D. G.
Published: February 2011

Results are presented of experiments on the lubricated sliding of metals on polymers over a range of speeds and temperatures. These results indicate a correlation between the frictional behavior of materials and their bulk mechanical properties. Support for the experimental correlations is presented in the form of a theory relating the coefficient of rolling friction to bulk mechanical properties. The general conclusions may be expected to hold for metals as well as other materials. The theory may also be expected to apply to well lubricated sliding where shearing forces have been minimized. Under the conditions of lubrication most commonly encountered, the sliding friction is expected to be much more complicated; both the shear properties of the boundary layer and the hysteresis characteristics will be important.
The Role of Rubber Hysteresis in Skidding Resistance Measurements
Authors: Giles C. G. , Sabet Barbara E.
Published: February 2011

In this paper the authors have tried to give examples of some of the more important ways in which Dr. Tabor's paper on the importance of rubber hysteresis has contributed to a better understanding of the mechanism of friction between tire and road. It is evident that a number of the problems presented by past test results may now be explained in terms of rubber hysteresis losses, in particular, the mechanism of the dependence of skidding resistance on temperature, and the differences in performance between natural and synthetic tires. In relation to testing techniques it draws attention to the importance of temperature and to the need to standardize the hysteresis loss properties of test tires in addition to the hardness of tread-rubber. Finally, the most important of all, as Dr. Tabor suggests, his work opens up the possibility of improvements in tire characteristics, which could result in greatly increased friction coefficients and hence greater freedom from skidding under wet conditions. The limited full-scale tests the authors have been able to make seem fully to confirm this possibility.
Friction of Rubber
Authors: Gough V. E.
Published: February 2011

It is not intended in this paper to attempt to mention all the wide variety of aspects of rubber friction which have been discussed in the literature. The objective is to draw attention to two interesting aspects, namely, that the maximum friction does not arise until some movement occurs and that, in the general case, velocity alone is not the sole deciding factor but rather that the friction developed is a function of a ratio of velocities. These phenomena appear to be fundamental to the behavior of rolling wheels and other dynamic friction problems. In special cases, more particularly those in which the relative sliding velocities are high, the frictional phenomena reduce to being velocity dependent. Experiments show that, while consistently high friction values are obtained at slow sliding speeds on rough emery cloth and similar surfaces (coefficients of 0.9– 1.5 say), the highest coefficients (2.5– 3.0 or even more) at slow sliding speeds are obtained on smooth glass and other materials with a glass-like surface (e.g. highly polished bakelite) provided the surfaces are clean and dry and the rubber surface is free from bloom or wax. This is consistent with the view that a high coefficient of friction is obtained provided the rubber itself makes contact with the other solid in some areas at least. Provided such surface films as are present are broken through, at least in some places, the necessary intimate contact is made and a high friction obtained. To ensure intimate contact between the main mass of rubber and a body with a smooth surface, both surfaces must be clean and dry or the rubber be shaped with a tread pattern capable of exerting a wiping action to remove the surface film. Not all surface films can be removed in this manner. For example, bloom on the rubber needs to be cleaned off in other ways, such as by rubbing with a rag dipped in solvent. In the case of rough or coarse textured materials the high stresses developed on the points of the surface ensures intimate contact by breaking through the surface films, even including bloom on the rubber. The presence of surface films of any kind would be expected to reduce the friction developed because in those areas in which they carry load they provide a medium of lower tangential shear strength than the bulk of the rubber and in many cases virtually act as a lubricant carrying the normal load with very low tangential drag. The suggestions above explain the small importance of cleanliness in the case of rough surfaces and the greater importance in the case of a smooth surface. The explanations agree, at least qualitatively, with the observation that the highest frictions are obtained on clean, smooth surfaces as then the maximum actual area of contact is possible.