bluuebunny/crossref_metadata_2025_split huggingface dataset:
Injection Molding of Rubber
Authors: Wheelans M. A. 
Published: February 2011

Abstract
The outline of a strategy for the injection molding of a safe mix is described. Safe accelerators, safe curing systems, and mixes are suggested with machine conditions which should yield short curing times for a wide range of products. Comparisons have been made of the vulcanizate properties of injection and compression moldings prepared from the same mix in the same mold and press at the same temperature. Results have shown that, although anisotropy is more pronounced in injection moldings, the mean of values for modulus along and at 90° to radial mold flow lines of an optimum modulus cure are the same (within experimental error) as the mean of values for modulus along and at 90° to mill flow lines in a compression molding also cured to its optimum modulus. Injection moldings are similar to compression moldings in volume swelling and hardness but they have marginally higher rebound resilience and marginally lower compression set. The effect of an increase in mold temperature is to give a valuable reduction in cure time, but it also causes a reduction in modulus and modulus dependent vulcanizate properties. Optimum values for maximum-minimum Monsanto Rheometer torque, relaxed modulus, and 300% modulus are reduced to 77– 79% of their optimum values at 160°C when cured at 200°C, but this reduction can be compensated for by adding higher levels of accelerator or accelerator and sulphur. Although a certain degree of anisotropy may have to be tolerated, the analysis of vulcanizate properties has provided a means of understanding and correcting an injection molding mix which fails to pass a specification. It gives confidence that NR can be cured at relatively high temperatures such as 180–190°C, which make injection molding profitable.
Effect of Composition on Shrinkage of Mold Cured Elastomeric Compounds
Authors: Beatty J. R. 
Published: February 2011

Abstract
The mold shrinkage of elastomer compositions depends upon the elastomer employed, the volume percent of elastomer plus all other organic materials, and the kind and amount of pigment present. The specific effects of pigments in inhibiting the shrinkage are shown. A procedure is given by which the shrinkage of most soft rubber compositions of the common elastomers may be calculated from the recipe. The major part of the shrinkage of elastomer compositions is due to the much greater thermal contraction of the composition than that of the mold. This portion of the shrinkage depends upon the thermal coefficient of expansion of the composition and mold and the temperature difference between the curing and room temperatures. A minor part of the shrinkage is due to a contraction in volume resulting from vulcanization. For normal soft rubber stocks with sulfur concentrations of three phr or less and for normal neoprene stocks, this factor may be neglected. For stocks having higher sulfur ratios an allowance needs to be made for this factor. Shrinkage of fiber loaded stocks should be determined carefully depending on the quantity, and particularly on the degree of orientation of the processed stock.
Application of Pulsed NMR to Elastomeric Composite Systems
Authors: Nishi T. 
Published: February 2011

Abstract
As has been shown, pulsed NMR can be applied to elastomeric composites in various ways. Other possible applications are to the study of crosslinking of elastomers; the effect of plasticizer, tackifier, or processing oil on elastomers; structure-property relationships for block copolymers (including polyurethane); liquid elastomers; thermoplastic elastomers, etc.; crystallization of elastomers under normal conditions or under extension. The advantages of pulsed NMR are that it is not affected by the physical state of the sample, the ease of temperature variation, and the short time required for data acquisition. However, it is necessary to choose the proper technique to analyse the system, and careful consideration must be taken of the effect of spin diffusion (for T1 measurement) and system recovery time, after a giant pulse for the measurement of free induction decay.
Cohesive Strength in Guayule Rubber and Its Improvement through Chemical Promotion
Authors: de Valle L. F. Ramos , Montelongo M. 
Published: February 2011

Abstract
Green (cohesive) strength of Guayule rubber (GR) was determined and compared to that of natural rubber (NR). In the case of GR gum compounds the green strength was shown to be inferior to that of NR gum compounds; however, in the case of black compounds GR green strength was similar to that of NR. Green strength was very much improved in both rubbers by the addition of MNNA (N-(2-methyl-2-nitropropyl)-4-nitroso aniline) for gum and black compounds. MNNA also acted as an accelerator and thus reduced the difference in vulcanization rate between NR and GR. When using MNNA, a reduction in energy consumption during mastication was also noted. Finally, MNNA notably increased the tensile modulus and decreased the elongation at break for GR vulcanizates, while maintaining an almost constant tensile strength.
Coupling Agents for Certain Types of Fluoroelastomers
Authors: Martin J. W. , Braswell T. V. , Green H. E. 
Published: February 2011

Abstract
From the data presented in this paper, it is concluded that fillers can be coupled with certain types of fluoroelastomer base polymers. A useful coupling agent must have mechanical and thermal properties at least equivalent to the base polymer in order to provide an improvement in properties for the compound under extreme service conditions. For the particular case of peroxide-curable fluoroelastomers and carbon fillers, hydroxy-terminated low-molecular-weight polybutadienes with high 1,2-microstructure appear to be good coupling agents. Care must be exercised in selecting the peroxide level to obtain a high crosslink density of the coupling agent while retaining rubberlike properties of the compound. This type of polybutadienediol has a relatively high number of reactive vinyl groups (approximately 20 per molecule) and relatively high molecular weight. Based upon the hypotheses presented in this paper, that coupling between carbon black and fluoroelastomers has been demonstrated for the first time, both higher molecular weight and multifunctionality of the polybutadienediol are viewed as important characteristics for effective performance.
Monitoring the Molding Process
Authors: Hindmarch R. S. 
Published: February 2011

Abstract
The monitoring of the molding process should be taken on as wide a scale as possible with a greater emphasis on the early stages of the process, incoming polymer and ingredients, mixing, blending, and cure studies, to reduce the need for very critical monitoring at the molding stage. Monitoring at a late stage in any process should not be aimed at identifying batch-to-batch variation, which has often been the case, but at achieving greater throughput of good product by optimizing the process and identifying machine faults.
Smoke Properties of Highly Filled Ethylene-Propylene-Diene Terpolymer Rubbers
Authors: Mosesman M. , Ingham J. D. 
Published: February 2011

Abstract
The observations made in this work indicate the difficulty in extracting generalizations about how efficiently hydrates serve to control smoke levels in a fire situation which involves periods of pyrolysis and of combustion. In our opinion magnesium hydroxide deserves serious consideration as a smoke retardant for EPDM rubbers. This is based on its superior performance in the flaming smoke test, its moderately good performance in the early part of nonfiaming smoke test, its high LOI, and its reinforcing properties. The electrical properties of the Mg(OH)2 filled EPDM rubber indicate that it could be acceptable for some types of electrical insulation or cable covering applications.
Degradative Effects of Guayule Resin on Natural Rubber
Authors: Keller R. W. , Winkler D. S. , Stephens H. L. 
Published: February 2011

Abstract
This study indicates that the degradative effects of guayule resin on natural rubber are due to the presence of unsaturated fatty acids in the resin. Since linoleic acid is, by far, the most abundant unsaturated fatty acid in guayule resin, it appears that linoleic acid is primarily responsible for the degradative effects of guayule resin on natural rubber. A possible mechanism to explain the acceleration of natural rubber degradation caused by linoleic acid can be developed by fitting linoleic acid into the Bolland oxidation mechanism for hydrocarbon polymers.
Adsorption of Sodium Dodecyl Sulfate on Natural Rubber Latex Particles and Determination of Specific Surface Area of the Particles
Authors: Chen S. F. 
Published: February 2011

Abstract
Soap titration of polymer latex is a widely used method for the determination of the specific surface area and particle size in synthetic latices. The method involves the titration of a latex of known polymer and soap content with a standard soap solution until the critical micelle concentration (CMC) is reached. At this concentration, saturation adsorption of the soap to form a monolayer on the particle surface occurs. From a knowledge of the amount and kind of soap adsorbed and the effective molecular area of the soap on the surface, the specific surface area and average diameter of the particles can be calculated. The effective molecular area of soap at saturation adsorption on polymer particle surface has been determined by comparing adsorption data with particle size data obtained by electron microscopy. Little information is available on the adsorption of sodium dodecyl sulfate (SDS) on NR latex particles. In ammoniated latex, these particles are covered by a complex mixture of proteins, fatty acid soaps, and lipids, the composition and concentration of which are not known accurately. Cockbain modified the soap titration method of determining particle sizes in synthetic latices and claimed that it was applicable to NR latices. In this method SDS was titrated to the latex adjusted to pH 6 ± 0.2. It was assumed that at this pH the interfacial activity of SDS was high while that of the proteins and fatty acid soaps initially present on the latex particles was comparatively low. Under these conditions the SDS would displace almost all the proteins and fatty acid soaps on the particles when sufficient SDS has been added to form micelles in the aqueous phase. The specific surface area was calculated from the SDS adsorption after assuming the molecular adsorption area of SDS to be 60 A˚. No account was taken of the effect of the poly(vinyl alcohol) creaming agent on adsorption. Sekhar found that Cockbain's method of soap titration was temperature dependent. Van den Tempel has shown that electron microscopy cannot yield accurate specific surface area of NR latex particles because of the heterogeneous particle size distribution inherent in unconcentrated latex.
Temperature Effect of Electrical Resistivity of Carbon Black Filled Polymers
Authors: Voet Andries 
Published: February 2011

Abstract
Very large positive temperature coefficients of resistivity (PTC) found in a narrow temperature range with dispersions of carbon blacks in noncrystallizing polymers are caused by an increase in average particle or aggregate distances of the dispersed black. This effect is the result of their deagglomeration upon temperature increase, induced by the increased Brownian motion, predominantly caused by the large reduction in vehicle viscosity and aided by the increase in segmental motion of the polymeric molecules. Highest PTC effects are found in the range of the steepest resistivity-concentration curves for the carbon black dispersion, differing markedly for each black and each polymer. The range itself is determined by particle size, density, degree of aggregation and agglomeration, and by the presence of surface oxides. In crystalline polymers high PTC effects are predominantly caused by the large volume expansion of the polymer in the melting range, as well as by the formation of a uniform melt from a two phase system of amorphous and crystalline components. Carbon black particles are mostly restricted to the amorphous phase in the solid, but are able to disperse into the entire volume of the melt. The effects of crosslinking the polymer as well as the influence of strain on PTC effects are considered. The decline in PTC effects above the peak temperature is discussed.
Role of Adhesion in Viscoelastic Properties of Rubber-Tire Cord Composites
Authors: Prevorsek D. C. , Sharma R. K. 
Published: February 2011

Abstract
Dynamic mechanical measurements have been carried out on samples of rubber and PET cord-rubber composites, with and without adhesive, as a function of strain amplitude, temperature, pretension, angle of strain application and time of cycling. The results show that mechanical loss and dynamic modulus depend on these variables as well as the presence and type of adhesive at the cord-rubber interface. Based on these results, we conclude that adhesion plays a significant role in the viscoelastic properties of a composite and it is an important factor along with the properties of components in the analysis of tire performance in terms of composite properties. This study clearly shows that the maximum adhesion may not be the optimum adhesion in tire technology. The most relevant question, i.e., the determination of the optimum level of adhesion for a specific tire, however, remains unanswered. The viscoelastic properties of the composites decrease with time of cycling but the rate of decrease depends upon the level of adhesion in the starting material. This result could be important in the development of a more realistic dynamic adhesion test. Attempts to use the viscoelastic experiments with small amplitude, high frequency strain to determine the onset of fracture in the composite specimen appears to be promising. Work is in progress to determine the potential of this method in the analysis of adhesion.
Mixing Process of Natural and Synthetic Polyisoprene Rubbers
Authors: Ponce M. A. , Ramirez R. R. 
Published: February 2011

Abstract
The mixing process, in a Brabender Plasticorder with a cam-type mixing head, was studied with NR (natural Hevea rubber), GR (natural guayule rubber) and IR (synthetic polyisoprene) at two different temperatures (60 and 80°C), with three types of carbon black (EPC, FEF and HAF), each one at three different concentrations (30, 50 and 70 phr). Samples for analysis were obtained at six different mixing times. Development of mixing and dispersion was evaluated through the black incorporation times (BIT), energy consumption, and tensile properties, which have been correlated to the degree of dispersion determined by low resolution microscopy. BIT, Optimum Mixing Times and the energy consumed to reach those points are lower for GR and IR than for NR. Compounds obtained at Optimum Mixing Times show that GR has a lower modulus, similar tensile strength and higher elongations.
Model Networks of End-Linked Polydimethylsiloxane Chains. X. Bimodal Networks Prepared in Two-Stage Reactions Designed to Give High Spatial Heterogeneity
Authors: Mark J. E. , Andrady A. L. 
Published: February 2011

Abstract
End-linking mixtures of very short and relatively long polydimethylsiloxane chains with a multi-functional alkoxy silane yields model elastomeric networks having a bimodal chain length distributions, and earlier studies have shown that this compositional heterogeneity increases the ultimate properties of the networks. The present investigation focuses on possible additional effects of the spatial heterogeneity introduced by the prereaction of some of the very short chains into tightly crosslinked domains. Increasing the extent of prereaction did not give any significant increases in modulus or ultimate strength. Thus, it is indicated that the unusual ultimate properties of bimodal networks are due to limited chain extensibilities, rather than to reinforcing effects.
Tack and Green Strength of Elastomeric Materials
Authors: Hamed G. R. 
Published: February 2011

Abstract
Tack and green strength are two important properties of many elastomer compounds. Tack is the ability of two materials to resist separation after bringing their surfaces into contact for a short time under a light pressure. Two types can be defined: autohesive tack (autohesion), where both materials have the same chemical composition and adhesive tack, in which the two materials have dissimilar compositions. The green strength of an elastomer is its resistance to deformation and fracture before vulcanization. Rubber stocks that are used in tire manufacture (or other plied-up operations) must have a certain minimum level of tack and green strength. Tack is necessary so that the many components of a green tire will hold together until molding. This requires not only that the components exhibit quick stick when building, but also that the tack bonds have long term creep resistance, since the green tire may be hung on a rack several days before molding and vulcanization. In addition, an uncured tire must have good green strength so that it will not creep and hence distort excessively before molding or tear during the expansion that occurs upon molding (or in the second stage for a radial tire). Adhesive tack is an important property of pressure sensitive tapes. Although some of the basic criterion necessary to obtain high autohesive tack or high adhesive tack are similar, this review will focus primarily on autohesion. Thus, unless otherwise staled, the term “tack” will refer to autohesive tack. However, ideas and results will be presented from the literature on pressure sensitive adhesives when such information leads to a further understanding of autohesion.
Probing Macromolecular Motions through Viscoelasticity
Authors: Ferry John D. 
Published: February 2011

Abstract
My personal random walk has included numerous other steps, including branches as well as closed loops that returned unproductively to square one. However, this is enough for the present occasion. I close with deep gratitude to the more than fifty graduate students and more than thirty postdoctorate and other associates with whom I have had the good fortune to collaborate over the years. Obviously, most of the work I have described is theirs, and I represent them in receiving the Medal. I apologize that only a few of their names have been mentioned here. I also thank the University of Wisconsin for providing an environment so favorable to research and scholarship and for supporting our work in many ways, direct and indirect. Finally, we have had financial support from numerous government agencies and several industrial firms, all acknowledged with gratitude. Once again, I deeply appreciate the honor I have received here and the privilege of speaking to you today.
Vulcanization of Butyl Rubber: Curative Effects of 2-Pentadecylbenzoquinonedioxime
Authors: Ghatge N. D. , Maldar N. N. 
Published: February 2011

Abstract
The structure-property relationships of butyl rubber vulcanizates derived from quinonedioxime-red lead or quinonedioxime-MBTS-sulfur cure systems were studied. The effects of the dioxime curatives on the mechanical properties of the elastomer are discussed on the basis of rheological and heat-aging study. It was found that a 2-pentadecylbenzoquinonedioxime-MBTS-sulfur cured butyl rubber vulcanizate shows good retention of tensile strength on heat aging at 125°C.
A Novel Optical Method for Estimating the Dispersion of Carbon Black in Rubbers
Authors: Ebell P. C. , Hemsley D. A. 
Published: February 2011

Abstract
The work reported is part of a large program aimed at examining the internal mixing of rubbers and its effect on properties. The dispersion of carbon black in the compound is of primary importance. Standard microscopical methods used industrially to measure this parameter are either subjective or lack discrimination at the higher levels of dispersion. To study mixing behavior effectively it is necessary to be able to assess the property over a wide range of degrees of dispersion. A technique based on the analysis of the dark field image produced by a reflected light microscope has been developed. The specimen preparation is simple, and analysis is carried out using a standard T.V. system. The technique gives results which are sufficiently discriminating to allow correlation of black dispersion with processing and mechanical properties, even at extremely high levels of mixing. An additional advantage of the method is that unvulcanized samples may be used.
Response of Carbon Black Filled Butyl Rubber to Cyclic Loading
Authors: Mckenna G. B. , Zapas L. J. 
Published: February 2011

Abstract
The stress softening behavior of a carbon black filled butyl rubber in cyclic loading (creep) and cyclic deformation (stress relaxation) histories was investigated. Single step and multiple step stress relaxation and creep experiments were conducted as were creep experiments with sinusoidal loading histories. The data were analyzed in view of the BKZ constitutive equation. For materials which follow the behavior predicted by the BKZ theory, the single step stress relaxation response is a lower bound for the stress in cyclic deformation histories, and the single step creep response is an upper bound for the deformations obtained in cyclic loading histories. In our experiments we observed that for filled butyl rubber, the responses to cyclic deformation and cyclic loading histories were outside these bounds. The softening was much more emphatic in cyclic loading histories than in cyclic deformation histories. We also found that the rubber is stiffer in creep than predicted from the BKZ theory (from stress relaxation data). It is suggested that an adequate description of material behavior might be obtained using a theory similar to the BKZ theory, which includes competing effects of stiffening in creep and softening under load-unload cycling. The failure lifetime of the filled butyl rubber in cyclic loading histories was related to the stress softening behavior. If it is assumed that, in some sense, a failure envelope exists, then it can be shown that under cyclic loading the filled butyl rubber should fail at a time earlier than under constant load conditions. We were able to predict failure lifetimes by using creep data obtained from short time cyclic loading histories and extrapolating to the strain at break determined from a shifted failure envelope. This approach relates the observed frequency and waveform dependence of failure lifetimes to the creep behavior under cyclic loading conditions.