bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical Reactions of Resorcinol-Formaldehyde Latex and Coupling Agent
Authors: Xue Gi , Koenig Jack L. , Ishida Hatsuo , Wheeler Don D. 
Published: February 2011

Abstract
In this study, the chemical reactions of the epoxy silane subcoat with resorcinol formaldehyde latex (RFL) topcoat were studied using model compounds. The experimental evidence indicated that various reactions took place between the γ-GPS and RFL. The epoxy group may react with the resorcinolic alcohol, methylol, and the residual silanol. Some reactions are catalyzed by NaOH or pyridine derivatives. Among the reactants, resorcinolic alcohol is the most active component in the presence of alkaline materials. It also has the highest concentration in an ordinary application. Thus, the resorcinolic alcohol opening the epoxy ring can be considered as the major reaction between the epoxy coupling agent and RFL. The 2-alkylpyridine component of the latex acts as a catalyst for the reaction. The residual silanol may consume the epoxy group upon heating during the processing. Since the reaction rate constant is low as compared to the silanol self-condensation and the interfacial reaction, and, furthermore, the concentration of the residual silanol is low, it will not influence the bonding at the silane/matrix interface.
Properties of Highly Filled, Highly Plasticized, Semicrystalline Polymer Networks
Authors: Vargo Richard D. , Kelley Frank N. 
Published: February 2011

Abstract
1. Component reactivity of ingredients such as fillers and plasticizers is significant and is measurable by a technique developed during this work. 2. The undesirable syneresis problem common to these highly plasticized materials can be controlled through adjusting equivalence ratios. Syneresis can be controlled primarily by decreasing the crystallinity of the material. 3. Changing percent crystallinity with temperature is a very important variable controlling the physical properties, i.e., ultimate properties, tearing energy, and dynamic-mechanical response. 4. The tearing energy data did not display simple amorphous behavior, and, as such, could not be shifted using a reduced variables technique such as WLF shifting. All variables were needed to represent the data. Three dimensional plotting developed previously by von Merrwall et al. was utilized to represent the data. The resulting tear-energy data exhibit the normal viscoelastic effects of rate and temperature as well as the superposition of the effects of crystallinity on the tearing energy. A decrease in tearing energy with increasing temperature is primarily due to increasing crystallinity in the samples. Plasticizer decreased the tearing energy, while filler increased the tearing energy. Filler lessened the effects of temperature and plasticizer on tearing energy. 5. Ultimate property measurements using ring samples for these model propellants revealed that these materials did not behave in a simple thermo-rheological manner, since crystallinity effects are predominant in the tensile mode. Because of crystallinity and strain-induced crystallinity, the data could not be represented by a failure envelope as proposed by Smith. The presence of plasticizer has the effect of decreasing the tensile strength, while filler tends to increase the tensile strength for the plasticized systems. 6. A model is presented to explain the high strain-to-failure behavior of these systems. Further details of this work can be found in Reference 22.
Reaction Kinetics and Injection Molding of Liquid Silicone Rubber
Authors: Batch Gibson L. , Macosko Christopher W. , Kemp Daniel N. 
Published: February 2011

Abstract
The curing of liquid silicone rubber (LSR) in an injection mold was studied using a two-pronged attack. First, a reaction kinetic model of LSR polymerization was derived from the hydrosilation mechanism. The model was tested with reaction kinetics of different rubber formulations with varying concentrations of catalyst and inhibitor. It was found that inhibitor consumption follows a zero-order kinetic model, and the subsequent polymerization kinetics are first order in vinyl concentration and concentration of available catalyst. Then this kinetic model was applied to a heat transfer and curing analysis which predicts gel time in a cavity of known thickness and mold temperature. Because silicone rubber has a low heat of cure, reaction exotherm was neglected in the analysis. The gel conversion was predicted using the recursive method, and thermal diffusivity was determined by transient temperature measurements in a cured slab. The predicted gel times were in good agreement with experimental demolding data. Because of its simplicity and accuracy, this analysis can be a useful tool for formulation optimization and mold-temperature selection.
Investigation of Rubber/Metal Bond Failures by Surface-Analysis Techniques
Authors: Madura A. R. 
Published: February 2011

Abstract
Surface-analysis techniques including ISS, SIMS, XPS, and SEM are highly complementary and are essential for detailed investigations of rubber/metal bond failures. Multitechnique investigations offer the most effective means of solving problems in bonding applications. EDS, a near-surface analysis technique usually associated with SEM, is a versatile supporting technique for comprehensive studies. Contamination of materials used in bonding applications, especially by silicones, is a commonly encountered factor in bond failures. However, the extent and role of the contamination is often difficult to assess. Prepared test coupons exposed to silicone spray mist considered significant in this study exhibit isolated regions of silicone contamination that did not severely influence peel-test failure modes or maximum peel-load values. The techniques used in this study can be used independently or together to identify surface-treatment effects, determine failure locus, verify the presence of conversion coatings, primers, and adhesives, and identify contaminants in rubber/metal bonding studies. Failure characteristics of bonded assemblies vary and are often complex. Failure investigations of a high-performance mount that exhibits regions of apparent interfacial failure show silicone contamination is present in the failure regions. Intact regions of the same mount failed by fracturing in liquid nitrogen do not contain silicone and show a different failure locus. This suggests that only limited areas of the part were initially contaminated to the extent that bonding was affected; or the regions disbonded in service were exposed to silicone contamination after the failure was initiated.
Combining Cobalt and Resorcinolic Bonding Agents in Brass-Rubber Adhesion
Authors: Hamed Gary R. , Huang J. 
Published: February 2011

Abstract
The bonding of several black-filled natural rubber vulcanizates to brass-plated steel cord was investigated using the TCAT pullout geometry. Compositions using either cobalt naphthenate or an HR bonding system (hexamethoxymethyl melamine plus RFR) had higher pullout forces than a control without these agents. However, the highest pullout forces, both initially and especially after aging, were obtained when the cobalt and HR additives were used together. Results from ATR spectra show that the RFR migrates to the brass surface, and it is proposed that this provides a barrier to attack by moisture of the brass-rubber interfacial region. In support of this idea, moisture uptake is reduced for compositions containing the HR bonding system. Moreover, in the presence of cobalt naphthenate, sulfidation of brass gives a surface topography of substantially higher surface area than seen if this agent is absent. This is expected to promote interlocking between the rubber and the outwardly growing sulfide layer. Finally, the HR resin is able to remove both zinc and cobalt from squalene solution. It is hypothesized that cobalt and the HR resin each have beneficial effects as noted previously, but the subsequent removal of cobalt from the rubber phase by complexing with the HR resin may prevent cobalt, a well-known oxidation catalyst, from promoting degradation of the rubber during aging.
Heat Generation in Elastomer Compounds: Causes and Effects
Authors: Medalia Avrom I. 
Published: February 2011

Abstract
In many important applications, an elastomer is subjected to repeated deformations of sufficient magnitude and frequency to lead to generation of considerable heat and (depending on the rate of heat removal) of a significant rise in temperature. The purpose of this review is to examine the mechanisms of heat generation and to indicate some important effects arising in service. More detailed discussion of various aspects of heat generation, dynamic properties, and viscoelasticity of rubber compounds may be found elsewhere.
Low-Temperature Properties of Hydrogenated Nitrile Rubber (HNBR)
Authors: Hayashi S. , Sakakida H. , Oyama M. , Nakagawa T. 
Published: February 2011

Abstract
HNBR, hydrogenated nitrile rubber, is a heat-, oil-, and fuel-resistant elastomer produced by the selective hydrogenation of NBR. As shown in Table I, HNBR is a highly saturated nitrile elastomer consisting of units of acrylonitrile, ethylene, unsaturated butadiene, and hydrogenated vinyl butadiene. The acrylonitrile gives excellent oil resistance, fuel resistance, and high tensile strength to NBR. The ethylene provides not only excellent rubber elasticity, heat resistance, chemical resistance, and ozone resistance, but also good low-temperature flexibility. The presence of a small unsaturated portion in the butadiene unit makes possible the easy vulcanization of HNBR with either sulfur or peroxide. The vinyl butadiene segments (6–8%) are preferentially hydrogenated at the beginning of the reaction and assist in maintaining the amorphous nature of the elastomer. The low-temperature flexibility of ordinary NBR varies in inverse proportion to its acrylonitrile content. Therefore, low-acrylonitrile NBR has better low-temperature flexibility than high-acrylonitrile NBR. The low-temperature properties of HNBR are different than those of NBR. This paper will show the relation between the acrylonitrile content and degree of hydrogenation and the glass-transition temperature (Tg) and low-temperature flexibility of HNBR. The Tg and low-temperature flexibility as measured by the TR-test and Gehman Torsional Stiffness test of HNBR showed the different behaviors for the various degrees of hydrogenation and acrylonitrile contents. Conversely, the brittle temperature of HNBR becomes lower with an increase in degree of hydrogenation. This paper also describes the effects of polymer composition and of various plasticizers on the low-temperature flexibility of HNBR.
Durability and Life Prediction of Adhesive Bonds in Severe Environments
Authors: Stevenson A. , Priest A. M. 
Published: February 2011

Abstract
1. Life Prediction methods may be used to characterize the durability of adhesive bonds of elastomers to rigid substrates. The primary rate determining mechanism of bond failure is considered to be electrochemical in nature, and its rate may be characterized on an Arrhenius basis. 2. Assumption of a single mechanism (and single activation energy) cannot be made across a wide temperature range. Two different regimes were discovered within the temperature range 20 to 90°C for both sea water and oil environments. 3. Durable bonds between elastomers and structural polymer/composites can be formed using normal rubber technology for rubber/metal bonding. In the case of bond durability in iso-octane/toluene at 90°C bonds of HNBR to E-glass composite surpassed those of HNBR to stainless steel. 4. These methods provide a scientific basis for quantitative determination of the life of engineering components in service. Further research is required at present for each new application, but wider use of these techniques in the future is anticipated, especially for critical applications where component replacement is costly or hazardous. This knowledge can provide confidence for engineers to make more extensive use of those adhesive systems in more demanding applications.
Filler-Elastomer Interactions. Part I: Silica Surface Energies and Interactions with Model Compounds
Authors: Wang Meng-Jiao , Wolff Siegfried , Donnet Jean-Baptiste 
Published: February 2011

Abstract
Inverse gas-solid chromatography, operated at infinite dilution, has been used to assess the surface energies of silicas, both fumed and precipitated. The dispersive components of the surface free energies of the silicas were calculated from the free energies of adsorption, corresponding to the —CH2— group, obtained from n-alkane adsorption. The specific components of the surface energies were evaluated separately by comparison of the free energies of adsorption of polar probes with those of n-alkanes, based on the surface areas covered by the probe molecules. The results indicate that while the dispersive components of silica surface energies is somewhat higher for the fumed silicas, the specific components are much higher for precipitated silicas, probably resulting from the higher silanol concentration on their surfaces. Moreover, the interaction able to take place between rubber matrix and the silicas are also estimated chromatographically from the adsorptions of low-molecular-weight analogs of elastomers. The free energies and enthalpies indicate that the interactions of functional groups with the fillers decrease in the order of nitrile, phenyl ring, double bond. The saturated rubber analogs show lower interactions with silicas. The lowest interactions of iso-alkanes imply poor interactions between butyl rubber and the fillers. As expected, the experimental data reflect an attenuation of polymer-silica interactions with decreasing content of functional groups and degree of unsaturation in NR, BR, SBR, and NBR.
The Examination of Diffusing Materials on Rubber Surfaces by Photoacoustic Infrared Spectroscopy
Authors: Peck M. C. Paputa , Samus M. A. , Killgoar P. C. , Carter R. O. 
Published: February 2011

Abstract
Minor amounts of diffusing materials can be beneficial or detrimental to the performance of elastomeric components. Methods to study these materials have been nonexistent or extremely time-consuming and insensitive for routine use. This report shows that photoacoustic detection Fourier-transform infrared spectroscopy (PAS-FTIR) is a simple method for in situ characterization of diffusing materials in elastomers. In this study, PAS-FTIR was used to monitor the appearance and diffusion of two vulcanization by-products to the surface of a carbon-black-filled natural rubber matrix. The compounds were identified from the PAS-FTIR spectra as a salt of stearic acid (most likely zinc stearate) and dimorpholinyl thione. Three rubber formulations, differing only in the particle size and surface activity of the carbon blacks used, were monitored by PAS-FTIR for a 135-day period to investigate the effect of carbon black on the diffusion of the compounds cited above. Diffusion of the dimorpholinyl thione was not affected by the carbon-black properties presented in this study. Larger carbon-black particle size delayed the appearance of zinc stearate on the vulcanizate surface.
NMR Imaging Studies of Vulcanized Butyl Rubber
Authors: Krejsa M. R. , Koenig J. L. 
Published: February 2011

Abstract
NMR imaging is a useful technique for studying the physical and spatial microstructure of cured elastomers. Different swelling agents can be used as chemical probes to detect varying amounts of microstructural differences. Imaging can be used to detect highly cured regions due to aging, poor mixing, and thermal gradients. NMRI is thus useful to study spatial distribution of crosslinks and is sensitive to changes in this distribution of crosslinks due to thermal gradients and the effects of aging and reversion processes. It can also be used to observed entrapped air in air-aged samples. Spin-lattice T1, relaxation times for solvent in cured elastomers have been shown to be shorter than the bulk solvent T1 values, providing a new method for determining the crosslink density. NMRI results have suggested that cure reversion and postcuring processes produce similar spatial results.
A Model for Tire Wear
Authors: Koutny F. 
Published: February 2011

Abstract
Tire abrasion arises due to slip in the contact of the tread with the road, and so it is closely related to the conditions of the road surface and weather. An attempt at phenomenological modeling of the treadwear process has been presented. A simple differential equation is set up to capture the dependence of the groove depth on the sum of tangential slips. It is shown that stochastic components of the usual meteorological quantities (temperature and humidity) may be approximated with a Markov series. A random process is suggested to simulate these environmental effects. Analytical solution of the model equation gives the average course of the groove depth and its confidence limits due to environmental effects. A nonlinear parameter estimation problem is formulated and several methods for its solution indicated. Some recommendations for circumventing possible difficulties are given. The capability ofthe model has been demonstrated by modeling experimental data. Finally, some aspects of linearization and the consequent simplification are mentioned. Beyond the choice of adequate parameters to represent environmental effects, in particular, geographical regions, other questions remain. For example, structure of the model parameters a, b or their relationship to each other requires further effort. On the other hand, the scope of the present ideas may extend beyond the problem of tire treadwear, perhaps having application in the modeling of weathering problems.
Characterization of Vulcanized EPDM Rubbers by High-Resolution Pyrolysis Gas Chromatography
Authors: Yamada T. , Okumoto T. , Ohtani H. , Tsuge S. 
Published: February 2011

Abstract
Pyrolysis gas chromatography (PyGC) is a powerful tool to give unique information of high polymers. Especially, PyGC is favorable for the practical analysis of insoluble polymeric materials such as vulcanized rubbers. In the previous paper, the structures of commercially available unvulcanized ethylene-propylene-ethylidenenorbornene rubbers (ENB-EPDMs) were investigated by high-resolution PyGC. The observed high-resolution pyrograms of the unvulcanized EPDMs were correlated to the ENB content. In addition, several peaks of the characteristic degradation products were interpreted in terms of the sequence distribution and the ethylene-propylene composition. In this work, vulcanized ENB-EPDMs (V-EPDMs) cured with two types of vulcanizing agents were studied using high-resolution PyGC. Characteristic pyrolysis products formed at 650°C were separated by the high-resolution capillary column, and the resulting pyrograms were interpreted in terms of ENB content in the vulcanized rubber samples. In addition, thermal degradation behavior of the ENB units in V-EPDMs was investigated.
Filler—Elastomer Interactions. Part III. Carbon-Black-Surface Energies and Interactions with Elastomer Analogs
Authors: Wang Meng-Jiao , Wolff Siegfried , Donnet Jean-Baptiste 
Published: February 2011

Abstract
The surface energies, both the dispersive component, γsd, and the specific component, γssp, of dry- and wet-pelletized carbon blacks, ranging from N110 to N990, were evaluated by inverse gas-solid chromatography at infinite dilution. The results indicate that the dispersive components of the surface energy of carbon blacks increase with increasing surface area. This dependence may essentially reflect an effect of microstructure on the surface energies, which can be confirmed by the relationship between the crystallographic parameters of crystallites and the graphitization of the carbon blacks. It was found that smaller crystallites characterized by a lower value of Lc lead to higher surface energy, whereas graphitization of the carbon black points toward lower surface energy, perhaps resulting from the growth of the quasi-graphite structure. Surface area dependence of the specific component of the surface energy characterized by the specific energy of adsorption of a polar probe follows the same pattern as was observed for the dispersive component, i.e., γsd increases with surface area. This is believed to be related to the crystallographic structure and the surface chemistry. Studies on adsorption energies of the low-molecular-weight analogs of elastomers generally show that the interactions between carbon blacks and rubbers depend not only on filler surface energies but also on the structure of the elastomers. Due to their polar functional groups, NBR and SBR show a stronger interaction with blacks than unsaturated rubbers. Among the rubbers simulated, IIR would have the lowest interaction with the filler. A comparison of the surface energies of carbon blacks and silicas points toward a very high γsd, for blacks which may show strong interaction with nonpolar- or low-polar polymers, while the very high Sf value of the silicas, especially precipitated silicas, a measure of the relative polarity of their surface, is considered to be representative of strong particle-particle interaction, leading to the formation of a filler network.
On the Anomalous Freezing and Melting of Solvent Crystals in Swollen Gels of Natural Rubber
Authors: Jackson Catheryn L. , McKenna Gregory B. 
Published: February 2011

Abstract
The anomalously large solvent freezing point depression, ΔTf, observed in crosslinked rubbers swollen in solvent has been a subject of study for over thirty years without clear resolution. While a sizeable ΔTf is accounted for by the lowering of the thermodynamic potential of solvent molecules in a polymer solution derived from the Flory theory, the additional ΔTf observed for crosslinked rubbers has been attributed to various physical effects such as restriction of solvent crystals to small size by the network mesh or difficulty in nucleation of the solvent crystals. In this paper, we identify two points of misunderstanding in the literature on this problem, and attempt to clarify the analysis of ΔTf for solvent swollen rubbers. The first point relates to the application of the Flory calculation to solvent freezing, where nucleation is a concern, rather than for solvent melting, for which it was intended. We present new calorimetric data on both the freezing and melting of solvent crystals in crosslinked and uncrosslinked NR swollen in benzene to illustrate this point. The second point relates to a reconsideration of the hypothesis of Kuhn et al., that the anomalous ΔTf-can be accounted for by small crystallite size. Although Boonstra and coworkers argued against Kuhn's hypothesis based on the results of x-ray line-broadening studies of solvent crystallite size, d, in the frozen gel, we have shown that their interpretation is suspect due to the use of an incorrect value for the solid-liquid surface energy of the solvent in the calculation of the melting- or freezing-point depressions.