bluuebunny/crossref_metadata_2025 huggingface dataset:
Oscillating Disk Curemeter Monitoring of Two-Part Polysulfide Sealants
Authors: Hanhela Peter J. , Huang Robert H. E. , Paul D. Brenton , Symes Theodore E. F.
Published: February 2011

By modifications to the dies and rotor of an oscillating-disk curemeter, continuous monitoring of features of the cure of two-part polysulfide sealants has been achieved. The principal innovations included use of a larger rotor and relocation of the parting line of the dies to the top of an enlarged cavity, which itself was altered in shape to a square design. By these means and through the introduction of an O-ring on the lower die, the fluid mixtures produced after introducing the sealant components were retained in the cavity. Reproducible torque-time curves were obtained using an arc of ±3°. The diverse applications of the procedure for studying curing variables have been demonstrated through examination of the influence of different curatives, curing ratios, liquid polymers, accelerators, fillers, dispersants, and the thermal resistance of cured sealants in confined spaces. The procedure has also been shown to provide a meaningful discrimination between sealants of different crosslink density. The value of the technique may be further enhanced through introduction of new instruments capable of providing loss factor (tan δ) measurements.
Quantitative Analysis of Vulcanized SBR/EPDM Diblends. Magic Angle Spinning 13C-NMR Experiments at 80°C
Authors: van der Velden G. P. M. , Kelm J.
Published: February 2011

A new quantitative expression has been derived in order to estimate the styrene-butadiene ratio from the 13C-NMR olefinic resonances. With the help of this expression, the cis-1,4, trans-1,4, vinyl-1,2, butadiene and styrene ratios could be determined. From the aliphatic region, subsequently, the ethylene and propylene contents could be determined and finally the SBR/EPDM blend ratio. From the 13C-solid-state-NMR spectrum, no evidence could be obtained for homo- or co-vulcanization. The 13C-NMR spectra of the blends are simply a co-addition of the 13C-NMR solution spectra of SBR and EPDM rubbers. No evidence has been found for cis-1,4/trans-1,4 ratio changes for SBR (in comparison to the starting material).
Orientation Effects in Rubber Double Networks
Authors: Roland C. M. , Warzel M. L.
Published: February 2011

The utilization of network structure to impart stable orientation to a rubbery material has been largely unexploited to date. It is demonstrated that the presence of a double network will amplify both the modulus and strain crystallizability of an elastomer, presumably without the disadvantages encountered in achieving these through simple increases in crosslink density. The high residual strains obtained via double-network formation are accompanied by surprisingly low levels of birefringence. The extent of molecular orientation necessary to engender high residual strain is evidently quite low, at least in so far as the former is reflected in a bulk macroscopic measurement such as birefringence. This low equilibrium birefringence, along with the absence of any measurable thermal crystallization effects, indicate that double networks are actually not highly oriented. As seen from their higher moduli and higher strain optical coefficients relative to single networks, and from their enhanced strain crystallizability, double networks are evidently very orientable. Investigation of this aspect of the behavior of double networks would likely prove fruitful, not only concerning these materials, but also with regard to obtaining a broader understanding of rubber elasticity. While the enhancement of strain-induced crystallization might suggest that rubbers with double networks will exhibit superior failure properties, this remains to be demonstrated. The crystallization results described herein clearly raise more questions than can presently be answered concerning the behavior of rubbers with double networks.
Rolling Loss of Pneumatic Highway Tires in the Eighties
Authors: Schuring D. J. , Futamura S.
Published: February 2011

Up to and including World War II, not more than a dozen papers had been written on the subject of tire rolling loss. The number quickly increased after the oil embargo in 1976 and reached a peak around 1980 with more than thirty papers published per year. Several symposia were held in these years on the subject, and a comprehensive review of rolling-loss research was written by one of the authors of this article. Other, briefer reviews were published at that time by Barson, who discussed various techniques of measuring tire rolling loss; Moore, who pointed out ways of reducing rolling loss and hence fuel consumption; Clark, who touched upon some physical phenomena of tire rolling loss; and Chang and Shackleton, as well as Levine, who reviewed the effects of tire construction and materials on rolling loss. The main concern at that time was to understand the mechanism of tire rolling loss so that it could be effectively reduced. Hence, accurate laboratory testing procedures were developed to identify the effects of major tire and service factors on rolling loss, such as tire type, geometry, reinforcement, materials, load, inflation pressure, speed, slip angle, temperature, and road texture. Concurrently, predictive models were developed ranging from simple empirical relations to complex finite-element programs, so that besides costly experiments, mathematical simulations could be employed as guidance toward lower tire rolling losses and thus meeting the stringent governmental fuel-economy standards. The efforts of the tire industry to reduce tire rolling loss have been very successful, and further progress is to be expected. Figure 1 gives an indication of the rolling loss improvements achieved over the past 15 years. The average rolling loss coefficient of a sample of radial passenger car tires manufactured in 1975 was 12.6 N/kN; its standard deviation was 1.3 N/kN. A similar sample of radial tires manufactured a few years later indicated an average coefficient of 11.0 N/kN with a standard deviation of again 1.3 N/kN. A check of recently manufactured (1989) radial passenger car tires revealed a further drop to 9.3 N/ kN with a standard deviation of only 0.4 N/kN. Hence, in the first years after the oil embargo, the average rolling loss was reduced by roughly 10%—without change of the rather broad dispersion, however. The following years led to further improvements of an additional 15%, this time with a drastic drop of variability. This indicates the effects not only of material and construction improvements but also of tighter controls in the production process.
Protection of Rubber against Ozone
Authors: Layer Robert W. , Lattimer Robert P.
Published: February 2011

Currently, chemical antiozonants can be considered to function by scavenging ozone and, in the process, forming a protective barrier to prevent further ozone attack. Therefore, antiozonants must do two things: 1. react more rapidly with ozone than the rubber and 2. in the process, form products on the surface which prevent ozone from reaching both the underlying antiozonant and the rubber. Presently, more work is needed to define exactly what characteristics are required for the ozonized products to serve as an effective barrier. However, indications are that they must have a higher molecular weight than the antiozonant.
Cavitation in Rubber: A Cautionary Tale
Authors: Gent A. N.
Published: February 2011

What can we conclude from this brief history of cavitation in rubber-like solids? At first, the condition for internal cracking appeared to be particularly simple. Whenever a stress was set up equal to the maximum possible stress calculated from simple elasticity theory, i.e., 5E/6, then cavitation ensued. But it is now clear that this criterion is only approximately true and then only for a certain narrow range of void sizes. Because cavitation is often found under the originally deduced conditions, voids are obviously present in rubber of an appropriate size, between about 0.1 µm and 1 mm in radius, at least when the volume of rubber is large enough to accommodate them. Thus, even though the original criterion was arrived at on a faulty premise, it has proved to be a useful and broadly applicable fracture criterion. In preparing this brief historical review, I have been led to some elementary conclusions about research itself. First, the fact that a theory appears to work does not mean that it is true. Secondly, even simple, carefully-selected, systems are often difficult to understand. And, finally, contributions from different points of view are essential to scientific progress.
Direct Measurement of Poisson's Ratio in Elastomers
Authors: Kugler H. P. , Stacer R. G. , Steimle C.
Published: February 2011

Poisson's ratio has been measured in a series of filled elastomers using a novel optoelectronic system. Relative precision of this measurement was found to be approximately 0.7% at 1% strain for this family of materials. The largest contributing error source was determined to be the tolerances that could be obtained in machining the surfaces of the test specimens. As a result of these errors, only three significant figures for Poisson's ratio can be achieved using this measurement approach. Material property tests conducted included constant strain rate and stress relaxation. Constant strain-rate results were used for general characterization, while the stress—relaxation data were employed to investigate time-dependent aspects of Poisson's ratio.
Binder/Filler Interaction and the Nonlinear Behavior of Highly-Filled Elastomers
Authors: Stacer R. G. , Hübner C. , Husband D. M.
Published: February 2011

1. The small-deformation-viscoelastic response of elastomers containing nonreinforcing filler has been investigated. Nonlinear viscoelastic behavior was observed as a pronounced strain-amplitude dependence. The degree of this dependence was quantified using a power-law representation as a single nonlinear parameter, m. 2. The magnitude of m was a function of formulation variables. It was found that m increased with the volume fraction and particle size of filler material, as well as the volume fraction of plasticizer. Reduced values of m were observed in the presence of bonding agent and with greater degrees of apparent crosslinking. The latter was controlled in this study through imbalanced urethane cures. 3. Nonlinear behavior of elastomers containing nonreinforcing filler has been compared and contrasted with the data base for carbon-black-reinforced elastomers. The major difference is in the effect of the surface area of filler particles. Nonlinear response in black-filled rubbers increases with surface area, while the opposite is reported in this study. Additionally, the relationship between viscoelastic dissipation and the magnitude of nonlinear response, well established for black-filled rubbers, was not observed. These results indicate that the response of elastomers containing nonreinforcing filler, although nearly identical in appearance to that seen with reinforcing filler, is not driven by the same mechanism. 4. A binder/filler interaction model is proposed for materials containing nonreinforcing filler. This model is based on the ideal adhesive strength of the binder/filler interface. In this model, greater attraction between polymer and particle surfaces reduces molecular slippage during deformation, leading to a decreased dependence of the modulus on strain amplitude, or decreased nonlinearity. It is shown that the model provides reasonable predictions for the observed phenomena.
Crosslink Distribution and Interfacial Adhesion in Vulcanized Blends of NR and NBR
Authors: Tinker Andrew J.
Published: February 2011

In contrast to expectations from rheometer studies of vulcanization behavior, the NMR technique has demonstrated that blends of NR and NBR vulcanized with sulfur/TMTM show a marked distribution of crosslinks in favor of the NR phase. The presence of even a minor proportion of NBR is sufficient to reduce the degree of vulcanization of the NR phase below levels deemed to be technologically necessary. Replacing the sulfur with a bis-alkylphenol disulfide reduces the degree of preferential distribution of crosslinks substantially. Interpretation of differential-swelling data for the blends on the basis of the swelling expected from a single polymer vulcanized with the same level of curatives as added to the blend gives the impression that the blends are lacking in interfacial adhesion. The interpretation enabled by the NMR estimates of degrees of crosslinking for the phases within the blends demonstrates that there is no lack of interfacial adhesion in blends of NR and NBR having a low acrylonitrile content, although blends containing a minor proportion of NR and vulcanized with sulfur/TMTM may show cohesive failure of the NR phase when the NBR phase is highly swollen due to the low degree of crosslinking of the NR.
Processing of EPDM Polymers as Related to Structure and Rheology
Authors: Beardsley Kenneth P. , Tomlinson Richard W.
Published: February 2011

We have shown that the rate of mixing oil and carbon black with EPDM polymers having the same Mooney viscosity is dependent on their molecular-weight distribution and degree of branching. Samples having broad molecular-weight distributions mix more slowly than samples with more narrow distributions, and branched samples mix more slowly than corresponding linear samples. The slower mixing of samples that are branched or broad in molecular-weight distribution is a consequence of their more elastic character. These samples tend to be more non-Newtonian in their flow characteristics and thus have high viscosities at low shear rate and low viscosities at high shear rate. They also drop more in viscosity on mixing with oil. These factors cause these polymers to wet the carbon black more slowly and to have lower shear stresses during the mixing, leading to slower mixing.
Interaggregate Interaction in Filled Rubber
Authors: Roland C. M. , Lee G. F.
Published: February 2011

Measurements of the dynamic properties of carbon-black-filled rubber can be carried out on most instrumentation at strains within the limits of linear behavior; thus, assessments of acoustic performance can readily be made. The equivalence of small-strain dynamic-mechanical testing and acoustic measurements has been demonstrated herein. Blends of NR with a high concentration of 1,2-BR are attractive candidates for damping applications because of the extended frequency range of the glass to rubber transition. One approach to improving the magnitude of the damping is to incorporate high levels of carbon black into the material. Significant interaggregate interaction, promoted for example by a low degree of carbon-black dispersion, will amplify the energy dissipation. The strain dependence of the dynamic properties implicit in such an approach can result in a damping performance sensitive to deformation. The loss tangent rises significantly after such a deformation, while the loss modulus experiences a barely measurable decline. This sensitivity to deformation will thus impact more on constrained layer damping applications than on simple extensional damping. For the materials tested in the present study, complete recovery of the damage to the carbon-black network (which engenders the changes in dynamic mechanical properties) required more than a day at room temperature.
Application of Fatigue Methods Based on Fracture Mechanics for Tire Compound Development
Authors: Young D. G.
Published: February 2011

It is important to develop laboratory fatigue methods which are predictive of tire performance to minimize development time and costs. A basic premise of this paper is that fatigue testing based on fracture mechanics principles has major advantages over traditional methods or those which attempt to simulate the geometry of the composite tire in the laboratory. Basic fracture-mechanics theory will be reviewed, followed by summaries of previously published studies. Three new studies will illustrate the wide applicability of the methodology.
FTIR Spectroscopic Studies of Miscible Polymer Blends
Authors: Yamada Kazuhiro , Funayama Yoshinori
Published: February 2011

The miscibility of IR and V-BRs with various vinyl contents has been investigated by using DSC and temperature-dependent FTIR spectroscopy, from which we conclude: 1. The glass-transition temperatures of the sequences which relate to the microstructures in IR and V-BRs can be detected by using temperature-dependent FTIR spectroscopy. 2. A miscible polymer blend exhibits a single Tg in DSC thermograms. But, judging from the infrared spectroscopic probe, the IR segments and the V-BR segments do not begin to move at the same temperature. When the data of infrared spectroscopy are compared with those of DSC, it would be possible to conclude that Tg− corresponds to the onset of the segmental movement of IR and then V-BR segments begin to move next, resulting in the broadening of the DSC transition region. 3. This broadening of the DSC transition region originates from the disparity of Tgs between IR and V-BR and may not be necessarily related to the onset of phase separation.
Aging of Tire Parts during Service. II. Aging of Belt-Skim Rubbers in Passenger Tires
Authors: Kaidou Hiroyuki , Ahagon A.
Published: February 2011

The belt-skim rubber of a passenger-car tire has changes in its tensile properties, M100 and λb, during service in the field. The changes are larger in higher temperature fields with an equivalent duration. It can be interpreted that the changes are caused simply by oxidative crosslinking similar to that which takes place on aging rubber sheets in an air oven at relatively low temperatures, below 100°C. The belt-skim compound showing better aging resistance in the laboratory also shows better aging resistance when used in a tire. Therefore, the aging characteristics of the rubber part in a tire can be satisfactorily predicted. The Arrhenius equations with the same activation energy can be used for the aging of a rubber in the laboratory and in the tires by introducing a factor to the tire equation. The factor is added to the atmospheric temperature to correct for a difference; however, it was found to be slight in the present case.
Polymerization of Ethylene with Propylene by Soluble Titanium (III) Catalyst
Authors: Makino Kenya , Hattori I. , Watanabe M.
Published: February 2011

Soluble TiCl3 complex catalysts were prepared by reduction of TiCl4 with hydrogen in the presence of Pd-carbon and ether in a halogenated hydrocarbon solvent. When copolymerization of ethylene with propylene was carried out with the soluble TiCl3 catalysts, the catalytic activities were very high, and copolymers obtained showed low crystallinity. When a small amount of a metal chloride was added to the soluble TiCl3 catalysts, it was found that the catalytic activity increased and the crystallinity of copolymers obtained was lower compared with those of the copolymers prepared by the original soluble TiCl3 catalysts. The copolymers obtained by the soluble TiCl3 catalysts showed high tensile strength (TB) and elongation at break (EB). From these results, it is concluded that the large values of TB and EB are caused from the microblock sequences of ethylene.
New Studies on the Surface Properties of Carbon Blacks
Authors: Ayala J. A. , Hess W. M. , Dotson A. O. , Joyce G. A.
Published: February 2011

A series of carbon blacks of widely varying morphology and microstructure were analyzed for surface compositional properties employing SIMS, XPS/ESCA, and GC-MS. These studies were supported by bulk analyses for hydrogen and oxygen content. Surface reactivity was assessed by means of inverse gas chromatography, moisture adsorption, and oxidation in an oxygen plasma. To directly assess carbon-black-polymer interaction, the carbon blacks were evaluated in SBR and IIR compounds for stress-strain and dynamic properties as well as bound rubber. The major findings of these studies are: 1. The combined results of hydrogen content, SIMS, and pyrolysis-GC-MS suggest a complex hydrogen functionality at the carbon-black surface, which governs the level of interaction with elastomers. 2. SIMS analyses have shown that the hydrogen functionality at the carbon-black surface is preserved after an 1173 K heat treatment in an inert atmosphere. 3. Gas-solid chromatography results indicate that this technique may be very useful to determine the degree of heterogeneity of a carbon-black surface. It also provides a tool to characterize the nature of the surface sites which are responsible for such a heterogeneity. 4. Moisture-adsorption rates provides a means to explore the reactivity of carbon-black-surface sites. Initial rates of adsorption can be well explained by a second-order-rate mechanism. 5. Bound-rubber development (SBR) and oxygen content per square meter of carbon-black-surface area were directly proportional to the hydrogen content of the black. The hydrogen content is considered to be the primary compositional factor relating to carbon-black-surface activity, while bound rubber and oxygen levels are specific measures of surface reactivity. 6. The slope of the stress-strain curves (or the modulus value) in the λ=1 to 3 region divided by the black networking factor, η (E′ at 2% ptp ÷ at 25% ptp), is sensitive to changes in black-polymer interaction. This ratio (σ/η or M/η) shows an excellent correlation with black hydrogen content and bound rubber (SBR). 7. The σ/η values for SBR and IIR are highly correlated, although the values for SBR are two to three times higher, and there was no measurable bound rubber for any of the IIR compounds. 8. The σ/η values for IIR (λ=2−3) and the oxygen/m2 values were found to be the best discriminators for black-polymer interaction in explaining within-grade treadwear variations in SBR/BR multisection radial-passenger treads.
People Make the Difference
Authors: Kastein Benjamin
Published: February 2011

The Las Vegas meeting of the Rubber Division, ACS, provided attendees the opportunity to hear the interview of Mr. Arnold H. Smith, by Mr. Herbert A. Endres, recorded April 7, 1966. Mr. Smith, as Secretary-Treasurer of the Division from 1919 to 1928, and as Chairman in 1929, was the person most responsible for laying the foundation which supported the growth of the Division to its present status. The India Rubber Section was sanctioned by the American Chemical Society on December 30, 1909. The 28 chemists from the rubber industry who were the organizing members, had the objective of meeting together to solve mutual problems. The major problem for everyone in 1909 was the variable quality of the 36 varieties of wild rubber from the jungles of Central and South America and Africa. Para rubber from the Hevea Brasiliensis tree was considered to be the best type available, but there were at least 13 variations, identified by source of the Para rubber. Charles C. Goodrich, as first chairman of the India Rubber Section, moved immediately to resolve the problem and appointed a committee, chaired by Dr. Charles Knight of Buchtel College, to develop standard methods of testing and evaluation. The committee diligently addressed the subject and reported to the Section at each meeting for 10 years, but progress was slow. Members attending had been instructed by their superiors, “Listen—but don't talk!” Not a very satisfactory format for conducting a meeting. Several key individuals helping to organize the India Rubber Section were W. C. Geer, Chief Chemist at the B. F. Goodrich Co. and George Oenslager, of the Diamond Rubber Co. Geer invented the air oven used to accelerate heat aging of rubber samples, and Oenslager is famous for discovering the effect on vulcanization of organic accelerators in 1906 and for the use of carbon blacks in treads in 1911. Although the sharing of technical information was tantalizing slow during the early years, the American Chemical Society, at their meeting in Buffalo, April 7, 1919, approved the formation of the Division of Rubber Chemistry. John B. Tuttle, first chairman of the Division in 1919, with Arnold H. Smith as secretary-treasurer, determined to bring to the members technical information less restricted in content, and from their neutral position of employment at the National Bureau of Standards, thought results could be obtained.
Gas Adsorption at Uniaxial Deformation of Filled Natural Rubber
Authors: Reichert W. F. , Göritz D.
Published: February 2011

Deformation dilatometers are used to measure the volume change of a sample during a deformation process. The sample is stretched in a sealed chamber and consequently a volume change of this specimen creates a pressure difference respective to a reference chamber. The conversion of the relative pressure change to a relative volume change is possible in the case no interaction takes place between the measurement medium and the sample. Liquids like mercury, silicone fluid, or diethylene glycol fullflll this assumption. On the other hand, gases used as measurement medium exhibit serious consequences on the registrated pressure change. Gas adsorption seems to be a plausible explanation for these effects. Cyclic deformation of a filled specimen shows that all adsorption places are formed during an initial deformation. Furthermore, TEM and ESI give insight into the morphology and the spatial distribution of the adsorbed nitrogen and oxygen. According to the model of inhomogeneous deformation, which is well represented by the observed morphology change of stretched, filled samples, one can calculate the increase of inner surfaces. The fitting parameters, describing the experimental data, are directly proportional to the filler content of the samples investigated here. All in all, we assume that the inhomogeneous deformation initiates the formation of inner surfaces which provide adsorption places for ambient gases. In addition to that, it points out that the measured volume effects of deformed samples have to be discussed in consideration of the applied medium. For example, gas adsorption causes an additional pressure decrease in the measurement chamber if air is used as the measurement medium.
Failure Properties of Silica-Filled Ethylene Vinyl Acetate Microcellular Rubber
Authors: Mukhopadhyaa Kinkar , Tripathy D. K. , De S. K.
Published: February 2011

The concentrations of the blowing agent and silica filler alter the microstructure of ethylene vinyl acetate rubber foam which in turn is responsible for changes in the physical properties of the foam vulcanizates. The theoretically predicted flaw sizes were found to be in reasonable agreement with the largest pore diameter observed from SEM photomicrographs. The results support the theory that the tensile rupture of foam rubber occurs by the catastrophic tearing from a flaw present in the form of the largest pore in the microstructure of the foam.
Development of an In-Situ Curemeter
Authors: Gent A. N. , Xie Kefu
Published: February 2011

An in-situ curemeter has been developed to follow the cure of thick articles during molding, by measuring continuously the dynamic mechanical properties (shear modulus and loss angle). It is a small-scale version of the Oscillating Disk Rheometer, designed to operate through the mold wall. An approximate theoretical treatment has been developed to relate the observed torque and loss angle to the dynamic properties of the rubber compound. Experiments were carried out with both unfilled and carbon-black-filled natural rubber compounds. Cure times measured by the curemeter were about the same as those obtained with the Oscillating Disk Rheometer. Modulus values inferred from the measured torques were compared with directly-measured values obtained from load-deflection curves for fully-cured specimens. Good agreement was found.
Bonding of Ultra High Molecular Weight Polyethylene to Styrene-Butadiene Rubber
Authors: Hamed Gary R. , Dweik Hasan S.
Published: February 2011

The adhesion between a sulfur-vulcanized SBR and polyethylenes (PE) of various molecular weights has been determined using a T-peel geometry. When the viscosity average molecular weight of the polyethylene exceeds about 700 k, bonding is sufficient to cause rubber tear during peeling. In contrast, with PE of Mv≈147k, joint strength is reduced by more than an order of magnitude and fracture proceeds between the SBR and PE. It is hypothesized that the high bond strength with the ultra high molecular weight polyethylene (UHMWPE) is due to the formation of entrapped tangles between chains of the two adherends. Consistent with this, SBR-UHMWPE bonds are not disrupted after extensive swelling in toluene.
Filler-Elastomer Interactions. Part VII. Study on Bound Rubber
Authors: Wolff Siegfried , Wang Meng-Jiao , Tan Ewe-Hong
Published: February 2011

SBR compounds were filled with 17 carbon blacks covering the whole range of rubber grades and tested for bound-rubber content. It was found that the bound-rubber content of a polymer at high loadings is higher for large surface-area carbon blacks. On the other hand, the bound-rubber content per unit of interfacial area in the compound (specific bound-rubber content) decreases with increasing specific surface area and filler loading. This observation was interpreted in terms of interaggregate multiple molecular adsorption, filler agglomeration, and change of molecular weight of rubber during mixing. When the comparison was carried out at critical loading of a coherent mass, the specific bound-rubber content was found to be higher for the high-surface-area products which are characterized by high surface energies. The critical loading of coherent mass of bound rubber also shows a strong surface-area dependence, indicating that large particle carbon blacks give high critical loadings. The measurements of bound rubber at high temperatures for carbon-black-filled compounds and in an ammonia atmosphere for silica-filled compounds suggest that bound rubber is caused essentially by physical adsorption.
Carbon Black Distribution in NR/Polybutadiene Blends
Authors: Massie J. M. , Hirst R. C. , Halasa A. F.
Published: February 2011

The distribution of carbon black between the phases of a NR/cis-1,4-polybutatdiene (BR) blend was studied. An N550 carbon black was added to the blend using different mixing techniques. The carbon-black distribution was determined using a variety of analytical techniques. The crystallization temperature of the BR was measured by differential scanning calorimetry. This temperature is related to the carbon-black level in the BR phase. Samples were dissolved in toluene to separate the bound and soluble rubber portions and the fractions were analysed for polymer type and amount by solid stale 13C MAS nuclear magnetic resonance. Results indicated that the N550 black has no preference for either the NH or the BR. In phase mixed samples, the majority of the black remains in tho polymer to which it is initially udded. When black and polymers are mixed simultaneously, the black tends to distribute itself uniformly between the polymers. Physical test results on a typical sidewall compound indicated that the location of the carbon black has a significant effect on physical properties, especially cut-growth resistance.
Styrene-Butadiene Rubber Filled with Fluorinated Carbon Black
Authors: Rodriguez J. , Hamed G. R.
Published: February 2011

A comparison is made of the properties of an SBR 1502 containing twenty volume percent of conventional furnace black, or one of three fluorinated blacks. Fluorination slows the rate at which the filler incorporates and disperses into the rubber. Final mixing torque decreases as the degree of fluorination increases, apparently due to a reduction in surface energy of the filler. Compositions with fluorinated blacks have reduced scorch times and decreased cure rates relative to compositions with normal furnace black. This is attributed to acidity of the fluorinated blacks. Scorch time increases in a linear fashion with pH of the filler. Tensile strengths of samples containing fluorinated blacks are about seven times that of a gum composition, but about 30% less than vulcanizates with regular furnace black.
Characterization of Immiscible Elastomer Blends
Authors: Hess W. M. , Herd C. R. , Vegvari P. C.
Published: February 2011

Considerable improvements have been made in the analysis of elastomer blends for composition, morphology and filler inter-phase distribution. GC, IR, NMR and thermal analysis (DTG, DSC, TG) techniques can provide quantitative information on composition. The latter three methods, along with SAXS, SANS, DMTA and microscopy (LM phase contrast, TEM, SEM, AFM) are also useful for resolving differences in blend homogeneity. The microscopical techniques are the most useful for characterizing morphology. TEM, in conjunction with cryosectioning and staining techniques, has provided the best means of resolving filler distribution to date. However, new AFM scanning modes may provide improved analyses in the future. Carbon black inter-phase distribution in blends of NR, SBR and BR can be controlled reasonably well by blending Banbury mixed masterbatches containing the desired carbon black loading in each polymer. Transfer of carbon black from one elastomer to another is favored by low unsaturation for the polymer originally containing the black, or a low heat history (e.g. solution and latex mixing) during preparation of the masterbatch. The overall polymer interaction with carbon black increases in the order: IIR, EPDM, NR, BR, SBR, the latter two being fairly close. Commercial carbon blacks will transfer extensively from an IIR Banbury masterbatch to NR, but not from EPDM to NR. Significant transfer to SBR occurs from both IIR and EPDM. Inert (partially graphitized) carbon blacks tend to distribute more evenly between the blend components regardless of which polymer contained them initially. Carbon black phase distributional variations can cause significant changes in unvulcanized and vulcanized rubber properties. For NR/BR and NR/SBR blends, reduced hysteresis generally occurs with a higher carbon black loading in the NR phase. Tear strength and cut growth tend to be maximized with higher carbon black in the continuous polymer phase, particularly when that phase is the higher strength polymer. The smaller the carbon black particle size, the greater the improvement in tear strength as a function of phase distribution. NR/BR fatigue life was maximized with about an equal distribution of carbon black in each polymer. This type of carbon black distribution also produced the greatest resistance to ozone cracking for NR/EPDM blends, which were further improved with very small domain size for the EPDM (disperse) phase. The abrasion resistance of NR/BR blends has indicated some improvement in the direction of higher carbon black in the BR. These results have been variable, however, and further study is needed for clarification.
Heat Transfer through Elastomeric Foams —A Review
Authors: Sirdeshpande Gourish , Khanpara J. C.
Published: February 2011

A balance has to be struck between the complexity of the models used to represent the heat transfer mechanisms and the amount of experimental information and the associated accuracy of information needed to verify these models. The solid, gas and radiation contributions can be treated as uncoupled, yet such a treatment can reasonably represent the heat transfer through foams. The solid contribution is a strong function of how the polymer is distributed between struts and cell walls, and the density of the foam. The radiation heat transfer through foams can be represented by diffusion approximation, and it is mostly absorption dominated. Therefore, measurement of the extinction coefficient is sufficient for adequate representation. The higher the extinction coefficient, the lower is the radiation contribution.
The Use of Skeletonization for the Shape Classification of Carbon-Black Aggregates
Authors: Herd Charles R. , McDonald Gerard C. , Smith Randolph E. , Hess William M.
Published: February 2011

A specialized image analysis erosion technique, termed skeletonization, has been used for the first quantitative and direct measurement of branching in carbon-black aggregates. Twenty different carbon-black grades were analyzed using transmission-electron-microscopy/automated-image analysis (TEM/AIA). The skeletonization data were used in a discrimination analysis program for detailed shape classification of carbon-black aggregates into four different shape categories that included spheroidal (Type 1), ellipsoidal (Type 2), linear (Type 3) and branched (Type 4). These data were used to examine differences in the aggregate shape distributions between and within grades. Skeletonization and conventional TEM/AIA analyses were also conducted to examine aggregate breakdown as a result of high-shear mixing in rubber (SBR) and cellulose acetate butyrate (CAB) paint chip compounds. It was found that the number of aggregate branches decreased by as much as 50% in rubber and 70% in CAB compounds, and the distributions became narrower. Aggregate breakdown increases in the direction of the larger particle size carbon blacks which contain more linear (Type 3) aggregates. In rubber, an N650 (131 DBPA) and N330 (102 DBPA) carbon blacks were found to be similar in overall aggregate shape properties. Therefore, the significantly higher vulcanizate modulus for N650 appears to be related to a higher level of carbon-black—polymer interaction, as opposed to high amounts of polymer occluded and immobilized within the aggregate structure.
Degree of Mixing Analyses of Concentrated Suspensions by Electron Probe and X-Ray Diffraction
Authors: Yazici R. , Kalyon D. M.
Published: February 2011

Two x-ray based techniques involving energy-dispersive analysis and diffractometry were introduced to the analyses of the degree of mixedness, i.e. the “goodness of mixing” of concentrated suspensions. A hydroxyl terminated polybutadene matrix was mixed with aluminum and ammonium sulfate. In the analysis, the ratio of the relative volume fractions of the two solid components was used as the basis of the analytical evaluation. Both characterization techniques are capable of determining the relative volume fraction of the two solid components as a representative measurement of the distributive mixing efficiency and both are sensitive to the scale of examination. The introduced techniques should be useful in the better definition of the degree of mixedness as well as in resolving differences in mixing efficiencies of various mixers used in processing of concentrated suspensions.
IBR Block Copolymers as Compatibilizers in NR/BR Blends
Authors: Zanzig David J. , Magnus Fred L. , Hsu W. L. , Halasa Adel F. , Testa Marty E.
Published: February 2011

The effect of the addition of 1,4-polyisoprene-1 ,4-polybutadiene (IBR) block copolymers on polymer compatibility and vulcanizate properties of a natural rubber/cis-1,4-polybutadiene rubber blend is studied. Differential scanning calorimetry and transmission electron microscopy are used to determine the degree of polymer compatibility and vulcamzate properties are measured in a sulfur cured, carbon-black filled rubber compound Block copolymer composition, concentration and molecular weight are found to be critical. Improvements in compatibility and vulcamzate properties are observed at low concentrations of IBR block copolymers.
Scanning Tunneling Microscopy of Carbon Blacks
Authors: Kim Seog-Jun , Reneker Darrell H.
Published: February 2011

Three kinds of carbon black, HAF (high abrasion furnace, N330), MT (medium thermal, N990), and graphitized MT were observed with the scanning tunneling microscope (STM), the transmission electron microscope (TEM), and the scanning electron microscope (SEM) All the STM images are formed from measurements of the x, t, and z position of points on the surface of the particle. The STM images of carbon blacks were compared to transmission electron microscope (TEM) photographs. Pitted and stepped bumps were observed on the surface of HAF carbon black. The surface of MT carbon black was more rough and disorganized At the atomic scale, ordered structure was found on the surface of HAF carbon-black particles Graphitized MT carbon-black particles were faceted polyhedra. Some facets were smooth while others had multiple terraces. The surface of graphitized MT carbon black was so well ordered that a lattice of carbon atoms similar to HOPG (highly ordered pyrolytic graphite) was observed on the smooth facets.
Rubber Viscoelasticity Using the Physically Constrained System's Stretches as Internal Variables
Authors: Johnson Arthur R. , Stacer Ross G.
Published: February 2011

The simulation of rubber viscoelasticity with the tube reptation model for topological interactions is investigated for large dynamic strains. The chemically crosslinked (CC) system of molecules acts as a constraint box per unit volume for the physically constrained (PC) system and carries the PC system during the deformation process. A stick—slip model is used to simulate the interaction between the CC and PC systems Stretch ratios describe the history of the PC system's energy. Rubber energy density functions for both the CC and time dependent PC systems are shown to model large strain viscoelastic deformations. In this approach the energy is split into two terms. The long term energy function for the CC molecules represents one part and a time dependent energy function for the PC molecules comprises the second part. The PC systems' stretches then appear as internal variables in the expression of the total energy. The relaxation of the PC molecules during a general deformation is determined by the history of the CC system's strain state and the box (tube) stick—slip relaxation equation(s). Examples are presented in which step-strain relaxation test data and strain rate data are simulated for large deformations of a rubber compound with differing short and long term energy functions.
In-situ Titration of Initiator-Consuming Impurities in Solution Anionic Polymerization
Authors: Monroy V. M. , Guevara G. , Leon I. , Correa A. , Herrera R.
Published: February 2011

An in situ titration of initiator-consuming impurities in amonic polymerizations, using 1,10-phenantroline as an indicator, was developed. The results show that even when impurities are present, it is possible to destroy them prior to the initiation of the polymerization reaction and achieve a better control of molecular weights by adding accurate known quantities of initiator.
Filler—Elastomer Interactions. Part IX. Performance of Silicas in Polar Elastomers
Authors: Tan Ewe-Hong , Wolff Siegfried , Haddeman Marinus , Grewatta Heinz Peter , Wang Meng-Jiao
Published: February 2011

Inverse gas—solid chromatography of silicas showed that the free energies of adsorption of polar probes were much higher than those obtained with n-alkanes. This implies that polymer—silica interaction is more pronounced in polar rubbers than in nonpolar rubbers such as polybutadiene. Using a series of silica and carbon-black-loaded acrylonitnle—butadiene (NBR) compounds with different acrylonitrile (ACN) content, this paper shows the changes in viscoelastic properties of the silica compounds can be attributed to improved polymer—filler interactions relative to the interactions involved in carbon-black compounds.
New Coagents in Peroxide Vulcanization of EPM
Authors: Dikland H. G. , Ruardy T. , van der Does L. , Bantjes A.
Published: February 2011

In a previous study, the mechanism of EPM peroxide vulcanization in the presence of various aromatic bis(allyl)esters was elucidated. It was concluded that the elastomer-coagent blend was phase separated and that during vulcanization chemical crosslinks are formed between the elastomer matrix and coagent domains. In this study the effect of the chemical structure of the coagent on the ultimate properties of the vulcanizate is reported. For this purpose a series of new coagents has been synthesized. It was found that bis(allyl) coagents with relatively flexible interlinking segments provide vulcanizates with improved mechanical properties.
Strain Energy Release Rates for Crack Growth in an Elastic Cylinder Subjected to Axial Shear
Authors: Gent A. N. , Wang Chi
Published: February 2011

Strain energy release rates have been calculated by finite element analysis (FEA) for various modes of failure of a long cylindrical elastic tube bonded between a rigid cylindrical core and a rigid surrounding tube. The core is subjected to an axial load so that the elastic tube is sheared. Fracture loads have been calculated for cracks propagating either along the interface or into the elastic material, at 45° to the interface, using linear elastic fracture mechanics and computed strain energy release rates. They are derived in terms of the initial crack size, the interfacial or bulk fracture energy, and the shear modulus of the elastic material. For an interfacial crack the failure load was found to be proportional to the tube length, the square root of the core radius, and a decreasing function of the elastic tube thickness, Ro/Ri. For a 45° crack, the presence of the rigid surrounding tube stabilized the crack at a certain size and an increasing load was needed to cause further growth. It is concluded that interfacial cracks are the most likely mode of failure.
Stiffness and Bond Strength of Rubber-Filled Hinges
Authors: Gent A. N. , Chang Y-W.
Published: February 2011

The stiffness of rubber-filled hinges for small rotations of the hinge plates has been determined by finite element analysis (FEA). The rubber is assumed to be linearly elastic and virtually incompressible, and the hinge is assumed to be long enough for the rubber to be in a state of plane strain, i.e., prevented from any displacement parallel to the hinge. Results have been obtained for hinges of a wide range of unstrained angle, ranging from 5° up to 360°. The calculated stiffnesses for long hinges vary by over four orders of magnitude over this range. For small angles, an approximate solution has been obtained by direct analysis—it is in good agreement with the FEA solution for hinge angles up to about 40°. Experimental measurements on several rubber-filled hinges are also reported. The measured rotational stiffnesses are in satisfactory agreement with theoretical predictions. Because a rubber-filled hinge constitutes a possible test method for bond strength, conditions are derived for bond rupture as a hinge is strained open.
Determination of Dynamic Bulk Modulus of Elastomers Using Pressure Measurement
Authors: Holownia B. P. , James E. H.
Published: February 2011

A novel method of determining dynamic bulk modulus of elastomers, by measurement of pressure changes of the fluid in which the specimen is immersed, was successful in principle. The frequency range covered was between 100 Hz and 1200 Hz which was limited by the power of the oscillator used.
Some Forms of the Strain Energy Function for Rubber
Authors: Yeoh O. H.
Published: February 2011

According to Rivlin's Phenomenological Theory of Rubber Elasticity, the elastic properties of a rubber may be described in terms of a strain energy function which is an infinite power series in the strain invariants I1, I2 and I3. The simplest forms of Rivlin's strain energy function are the neo-Hookean, which is obtained by truncating the infinite series to just the first term in I1, and the Mooney-Rivlin, which retains the first terms in I1 and I2. Recently, we proposed a strain energy function which is a cubic in I1. Conceptually, the proposed function is a material model with a shear modulus that varies with deformation. In this paper, we compare the large strain behavior of rubber as predicted by these forms of the strain energy function. The elastic behavior of swollen rubber is also discussed.