bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shrinkage of Cured Fluoroelastomers. I. Basic Parameters
Authors: Fogiel A. W. , Frensdorff H. K. , MacLachlan J. D. 
Published: February 2011

Abstract
The thermomechanical analyzer (TMA) is eminently suitable for the measurement of the thermal expansion coefficient of rubbers, provided the equipment is calibrated with materials of similar expansion coefficient. FKM or other thermally stable and amorphous polymers (of independently determined thermal expansion characteristics) can be used as calibration standards. The relative simplicity and precision of the TMA method for the determination of the coefficient of isotropic linear expansion, and hence, of volumetric expansion of rubbers, makes this important thermodynamic parameter easily accessible experimentally. Because of the frequently observed anisotropy of molded elastomeric compounds, measurements in all three dimensions are required to define linear, isotropic expansion and shrinkage which, to an excellent approximation, are represented by arithmetic averages of the three unidirectional values. Good agreement has been found between the average (isotropic) shrinkage determined experimentally and that calculated from the average (isotropic) coefficient of linear thermal expansion, α. The effect of fillers, such as carbon black, on α is additive. This makes it possible to predict α and shrinkage of all filled compounds from a single value of α of the unfilled rubber. The linear thermal expansion coefficients of the tested rubbers (FKM, NBR, EPDM) increase linearly with temperature, the increase being generally stronger for FKM than for the other elastomers. The appreciably higher mold shrinkage of FKM relative to NBR is directly due to the higher α of FKM for comparable levels of fillers. This must be kept in mind when expedience dictates the use of the same molds for FKM and NBR compounds.
Shrinkage of Cured Fluoroelastomers. II. Shrinkage Control
Authors: MacLachlan J. D. , Fogiel A. W. 
Published: February 2011

Abstract
Processing variables have been examined for the prediction and control of mold shrinkage in directions pertinent to practical applications. (1) Of the total shrinkage of finished parts, more than 75% results from the press cure, and the remainder is the result of weight losses during the subsequent oven cure. (2) Mold shrinkage may be reduced by addition of CaO, bituminous coal fines, or epoxy resins. Shrinkage can be increased by addition of volatile materials. (3) Control of shrinkage may also be effected with acicular fillers or filler mixtures through fiber orientation in the elastomeric matrix in the desired direction. In the case of O-rings, inside diameter shrinkage values ranging from zero to three per cent can be produced in a controllable manner by blank preparation techniques commonly used in the industry.
Rheological Characteristics of Gum Elastomers
Authors: Nakajima N. , Collins E. A. 
Published: February 2011

Abstract
A systematic characterization of gum elastomers may be done by measuring viscoelastic and ultimate properties. The viscoelastic properties of amorphous elastomers can be reduced to a master curve by means of the temperature-time, pressure-time, and strain-time correspondence principles. If a structure, e.g. crystallinity, develops with a change of temperature, pressure, or strain, such structural change may be regarded as a deviation. The ultimate properties may be represented either as stress-strain at break, modulus-strain at break, rupture-energy-deformation-rate, or stress-at-break-deformation-rate and strain-at-break-deformation-rate. The modulus-strain-at-break plot shows promise for interpreting mill processability in terms of the basic rheological properties. The rupture-energy-deformation-rate plot supplies a useful quantitative input for mill mixing.
Heterogeneous Blends of Polymers. Rheology and Morphology
Authors: Avgeropoulos G. N. , Weissert F. C. , Biddison P. H. , Böhm G. G. A. 
Published: February 2011

Abstract
A single polymer pair (BR and EPDM) was used to confirm experimentally rheology-morphology relationships that have been previously gleaned from comparison of a variety of blend systems. The relative importance of the primary factors which govern blend morphology (composition and relative mixing viscosity of the components) was determined over the range of practical interest. In addition, correlation of mixing rheology with more accurate and complete shear modulus data allowed (a) molecular interpretation of rheological behavior in terms of network parameters, such as physical entanglements, and (b) estimation of the elastic and loss components of the shear modulus during mixing. An attempt was made at explaining the dependence of blend morphology on the viscoelastic properties of the components in terms of a fracture or tearing mechanism.
Densities of Amorphous Polymers at High Pressures
Authors: Beret S. , Prausnitz J. M. 
Published: February 2011

Abstract
Experimentally determined densities and compressibilities of amorphous polymers are frequently available; but, because of experimental difficulties, few experimental results have been reported at high pressures. Such densities, however, are sometimes required for rational design of extrusion and similar processes. We report here a simple method for estimating densities and compressibilities at high pressures from experimental compressibilities at low pressure. Our method is based on a relation for liquids suggested by Wada and developed by Chueh and Prausnitz. The purpose of this note is to suggest a method for estimating polymer densities at high pressure wherever experimental data are insufficient for obtaining parameters needed in an equation of state, as, for example, the Tait equation.
Variations in Testing Procedures on the Rotary Flexometer
Authors: Kainradl P. , Wolf F. , Ecker H. 
Published: February 2011

Abstract
The rotary flexometer described in German Standard Proposal DIN 53 533 has been used to determine heat generation and fatigue resistance on homogeneous rubber specimens, laminated specimens, and some containing fabric plies. When a series of compounds having a range of hysteresis or hardness is run at constant deformation amplitude, the ranking is usually inverse to that obtained when run at constant force amplitude. The test method should be chosen to correspond to the proposed use of the compound. Accessories developed permit testing of 10 ×. 10 mm cylindrical specimens as well as conventional 20 × 20 mm cylinders. Temperature measurements in the specimen center have proven to be more precise than those on the free surface or on a clamped surface. Temperature increase during cycling is strictly a function of the viscoelastic properties of the compound. Creep measured at ambient temperature may rate a series of compounds differently than if measured at an elevated temperature. Fatigue resistance is well represented by S-N curves where the logarithm of N, the cycles to failure is plotted as a function of S, the severity factor (deformation amplitude or force amplitude). An inverse relationship exists between rate of heat generation and failure by degradation of the specimen center. The vulcanization system affects fatigue life. The temperature reached during testing of a highly hysteretic material can be minimized by using it as the central layer of a laminated specimen and higher hysteretic materials for the rest of the specimen. The apparatus can be used for testing dynamic adhesion fatigue of rubber-fabric bonds. Failure between plies started as a failure of the bond between rubber and cord.
Measurement of Molecular Weight Distribution of SBR and Prediction of Rubber Processability
Authors: Smith B. R. 
Published: February 2011

Abstract
This investigation on the origins of variable processability of emulsion SBR as measured by the BIT test established that no simple relationship exists between Mooney viscosity and processability, and that molecular weight distribution must be considered when producing to a BIT specification. By devising a sample preparation method directly from latex and the peak-height-ratio technique, a rapid method of estimating BIT from GPC chromatograms was developed. The method is suitable for process control. The mixing studies showed a general trend of increasing die swell with increasing BIT. The soluble rubber phase was found to have the same molecular weight distribution irrespective of the distribution at the commencement of mixing. It appears that die swell is influenced by variations in carbon-gel.
Compound Processability and Molecular Weight Distribution of SBR
Authors: Mills W. , Giurco F. 
Published: February 2011

Abstract
Nonuniformities in the mixing and extrusion behavior of nominally standard grades of emulsion- and solution-polymerized oil-extended SBR are associated with variations in molecular weight distribution but are not reflected by Mooney viscosity. The variations in the samples studied were representative of normal production material. The solution-polymerized polymers characteristically exhibit wider variations in compound die swell and have generally more rapid dispersion of carbon black than comparable emulsion-polymerized polymers. This is true, regardless of whether BIT or t′ point is considered as a measure of carbon black dispersibility. Generally, increasing polydispersity increases compound die swell and retards the rate of carbon-black dispersion. Utilization of unit work instead of mixing time as a measure for torque rheometer processability gives similar information on carbon-black dispersibility. However, unit work is preferred because of the promise it holds for scaleup and interlaboratory correlation. Delta Mooney values, and to a lesser extent peak Mooney torque, provide a useful basis for predicting the mixing and extrusion behavior of oil-extended SBR. The torque rheometer t′ point recently proposed as an index for carbonblack dispersibility is also useful for predicting compound die swell.
Synthesis and Properties of Uniform Polyisoprene Networks. I. Synthesis and Characterization of α,ω-Dihydroxy-Polyisoprene
Authors: Morton M. , Fetters L. J. , Inomata J. , Rubio D. C. , Young R. N. 
Published: February 2011

Abstract
The results of this study are the first to show that high-1,4 linear α,ω-dihydroxypolydienes can be synthesized with (a) predictable molecular weights, (b) narrow molecular weight distributions, and (c) high functionalities. Using the functionalized polyisoprenes prepared in this work, a series of networks was prepared with a purified triisocyanate as the chain linking agent. The soluble fraction in these networks ranged from 4.6 to 1.6 per cent. The characteristics and physical properties of these networks will be the subject of a forthcoming publication.
N-(Aminothio)imide Cure Modifiers
Authors: Lawrence J. P. 
Published: February 2011

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.