bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Influence of Carbon Black, Mixing, and Compounding Variables on Dispersion
Authors: Hess W. M. , Swor R. A. , Micek E. J. 
Published: February 2011

Abstract
A series of response equations relating dispersion and rubber properties to mixing and compounding variables have been developed for formulations based on SBR and EPDM. These provide insight on the relationship of dispersion to rubber performance as carbon black type and loading are widely varied. Optimum conditions have been defined for minimizing Banbury mixing time and power consumption to achieve acceptable dispersion for different grades of carbon black. The different blacks can be classified in terms of their relative tendency to be shear-stress or shear-strain sensitive. The finer, low-DBPA carbon blacks such as N326 are shear-stress sensitive. To achieve high dispersion levels, this type of black requires initially high compound viscosities, i.e., by means of high loadings, withholding all or part of the extender oil until after black incorporation, or by high black/oil ratios. The coarser, high-DBPA carbon blacks such as N650 are more shear-strain dependent and will reach high dispersion levels if enough energy (usually relatively low) is imparted to the batch during Banbury mixing. N650 consistently gave high dispersion levels over a wide range of black/oil levels, regardless of the polymer type or mixing variables. Carbon black dispersibility in SBR-1500 was improved in the direction of increasing DBPA and decreasing surface area. The surface area response was most pronounced when loose oil was added with the black. High oil with the carbon black tends to form harder, more persistent agglomerates which have a greater depressing effect on rubber strength properties such as tensile and fatigue. The effect of carbon black surface area on dispersion was considerably less in SBR-1712 with no loose oil addition. In EPDM, upside-down mixes of different grades of black at varied black/oil loadings produced some notable changes in the dispersion response to carbon black DBPA. At some of the high black/oil ratios, low DBPA was actually beneficial to dispersion. The finer, higher-DBPA blacks such as N351 showed a tendency to form more persistent agglomerates analogous to conventional SBR-1500 mixes in which high amounts of loose oil are added with low-DBPA blacks. These persistent agglomerates are most prone to form in an EPDM upside-down mix when the oil loading is close to the absorptive capacity of the carbon black. The Banbury power profiles of such compounds indicated a high initial peak and a depressed or missing second peak. A normal power profile and a high level of dispersion were achieved with these problem mixes when 25 to 50% of the oil was withheld until after black incorporation. N650 gave excellent dispersion in EPDM at all black/oil loadings and only minimal variations in vulcanizate properties were observed at mixing times ranging from 1 to 5 min.
Buckling of Viscoelastic Columns. Part II: Constant Deformation Rate Buckling
Authors: Wang Shau-Chew , Meinecke Eberhard A. 
Published: February 2011

Abstract
The buckling of viscoelastic columns has been considered from both a theoretical and an experimental perspective. The fact that buckling occurs at relatively low strain where the SBR is nearly linearly viscoelastic allowed several simplifications in the theoretical development, leading to closed form predictions of the loading and unloading curves. This treatment neglects gravitational effects and carbon secondary structure effects and fits the experimental data best at HAF loadings around 30 phr. At lower carbon black loadings, the gravitational effects caused the experimental Euler load to be less than predicted from linear viscoelasticity theory, while at higher carbon black loadings, the carbon black structure led to higher Euler loads than predicted.
Modification of Natural Rubber Latex with Peracetic Acid
Authors: Gelling I. R. 
Published: February 2011

Abstract
1. The structure of the products obtained from the reaction of NR latex with peracetic acid depends on the reaction conditions. 2. Under controlled conditions, specific levels of epoxidized NR (ENR) can be obtained. A random epoxide distribution has been observed. These materials undergo strain crystallization and hence exhibit good strength properties, although at high levels of epoxidation there is a decrease in the degree of crystal-unity. Other properties, e.g., hysteresis, air permeability, and oil resistance, change systematically with the level of epoxidation. These properties indicate that ENR has the potential to become an extremely useful commercial polymer. 3. At higher acid concentrations and/or temperatures, ring opening of the epoxide groups occurs, and even low levels of ring-opened structures have been found to adversely affect the properties of ENR. 4. The nature of the ring-opened structures depends on the degree of epoxidation. At low levels of epoxidation, where the majority of epoxide groups are isolated, simple diols and hydroxyacetates are formed. However, at higher epoxide levels, where blocks of epoxide predominate, the major product is a five-membered cyclic ether. At 100 mole% modification, a white amorphous thermoplastic product was obtained consisting almost entirely of furan structures.
Anisotropy Induced in an Uncrosslinked Elastomer Via Large Strain Deformation
Authors: Hamed G. R. , Song J. H. 
Published: February 2011

Abstract
The anisotropy induced in an ungelled SBR elastomer upon large scale deformation and the rate at which the deformed elastomer returns to its original state upon removal of the deforming force were investigated. In these experiments, a standard birefringence technique was unsuitable for measuring the extent of orientation after release, however, tensile stress-strain measurements successfully showed the presence of anisotropy. After prestraining and then releasing, samples have an initial resistance to deformation which is the same both parallel and perpendicular to the prestraining direction. However, testpieces cut parallel with the prestraining direction show stress-strain curves that lie above those for cross-cut specimens at high elongations, while cross-cut samples have stress-strain curves remarkably similar to those of the isotropic controls. With increasing time after prestraining or for larger prestrains, the normalized anisotropy, at intermediate elongations, becomes negative; that is, in this region, it becomes easier to deform “parallel” specimens than to deform “perpendicular” specimens. This phenomenon is proposed to be the result of two opposing entanglement networks—an original one, which remains in tension, and a compressed one, which was formed by chains re-entangling while the sample was extended. Although the shapes of the “parallel” and “perpendicular” stress-strain curves may be quite different, the total energy required to rupture the samples in both cases is similar. Finally, for a lightly crosslinked sample, it is demonstrated that after various prestrains, hold times, and relaxation times before testing after prestraining, the normalized anisotropy is a unique function of the residual extension at the moment when the specimens were tested.
Pulsed and Steady Field Gradient NMR Diffusion Measurements in Polymers
Authors: von Meerwall Ernst D. 
Published: February 2011

Abstract
Some twenty years after the development of the steady and pulsed gradient spin-echo NMR methods of measuring self-diffusion, these techniques are now maturing and experiencing a surge of interest, much of it concentrated on polymer systems. The methods are briefly reviewed here, together with the most important results in polymers, with particular concentration on work described within the last few years. The research is divisible into three categories: diffusion of diluent and penetrant molecules in rubbery high polymers, diffusion of polymer molecules in dilute and semidilute solutions with liquid solvents, and diffusion of macromolecules dissolved in concentrated solutions or melts of equivalent or different polymers of arbitrary molecular weight. The review includes the main theoretical interpretations of the experiments, particularly the free-volume theory in its various forms and power-law behaviors postulated by recent refinements of tube/reptation and scaling theory. This article represents an updated elaboration of an earlier review.
Oxidation and Ozonation of Rubber
Authors: Keller Robert W. 
Published: February 2011

Abstract
With the wide variety of elastomers, fillers, and other compounding ingredients available today, there is increasing demand for rubber compounds with specific properties. The systematic development of the desired rubber compound can be undermined by the exposure of the compound to oxygen and ozone during use. Thus, a rubber compounder should be aware of the effects of oxygen and ozone attack on rubber and how to compound for oxygen and ozone resistance. This short review is intended as an introduction to the phenomena of oxidation and ozonation of rubber.
Study of the Effect of Soft-Segment Length and Concentration on Properties of Polyetherurethanes. II. The Effect on Mechanical Properties
Authors: Petrović Zoran S. , Budinski-Simendić Jaroslava 
Published: February 2011

Abstract
Three series of segmented polyurethanes with different soft segment lengths and concentrations were examined by TMA, DMA, and mechanical methods. Maximum tensile strengths were obtained when ssc was 40–50%, which was explained by a specific interlocking morphology. No significant effect of soft-segment chain length on maximum strength was found, but higher values were found in the C series when ssc was 60%. Elongation at break increases linearly with ssc but indications that shorter soft segments produce higher extensions was attributed to plastic flow. TMA showed that Tg was independent of ssc in the C and, to a degree, in the B series, while temperature of α-transition in DMA was independent of ssc only in the C series at ssc above 50%.
New Accelerators for Vulcanization of Rubber—Part III: Synthesis, Characterization, and Evaluation of Some 2-Mercaptobenzimidazole Derivatives
Authors: Pal D. , Khamrai A. , Adhikari B. , Dutta T. , Maiti Mrinal M. , Maiti Sukumar 
Published: February 2011

Abstract
Five derivatives of 2-mercaptobenzimidazole containing S—N bonds have been synthesized and evaluated for their action as accelerator-antioxidant in NR gum stocks. All these compounds exhibit varying degree of accelerating efficiency; some of them, viz. MBSTP, MBSPT, and MBDSPT, offer excellent cure characteristics and vulcanizate properties comparable to some of the best commercially available curatives such as CPTD. Substitution at the N or S atom of the MB molecule does not affect adversely its antioxidant properties; rather, an improvement in aging resistance has been achieved. The degree and nature of substitution play an important role in the antioxidation properties of these MB derivatives. Thus, disubstitution offers better antioxidation characteristics than monosubstitution, and the latter, in turn, is better than unsubstituted MB. Some discussion on correlation of reactivities of these MB derivatives and their cure synergism with CPTD have been reported. It was observed that these new accelerator—antioxidant compounds show very little cure synergism with CPTD but do show promise as dual-function curatives for natural rubber.
Natural Rubber Compounds for Truck Tires
Authors: Barnard D. , Baker C. S. L. , Wallace I. R. 
Published: February 2011

Abstract
An 80 NR/20 BR truck tread compound containing a semi-EV cure system and modified with a 6.0 phr level of stearic acid has been shown to exhibit excellent resistance to reversion when compared to a similar compound containing a normal 2.0 phr level of stearic acid. Improvements in the retention of laboratory abrasion resistance, heat generation, and most physical properties have been identified on test pieces subjected to typical truck retread overcure conditions. In highway fleet testing trials of 1100 × 22.5 truck retreads fitted to both third and fourth drive axles of tipper trucks, the modified compound displayed a 42% improvement in treadwear performance over the normal compound in the lower severity third axle positions while performance in the higher severity fourth axle positions was inferior by 20%. In comparison to a 55 SBR/45 BR truck tread, both NR compounds displayed superior wear performance on the fourth axles while some further adjustments of the modified compound are required to match the synthetic compound on the third axles. The reversal of wear performances for all compounds between third and fourth axles is due to the different abrasion mechanisms encountered. Laboratory abrasion rankings do not correlate with wear performances of compounds on the fourth drive axle of trucks, but they do correlate with wear performances on third drive axles. Despite the reversion characteristics of the normal semi-EV compound, no significant adverse effect on treadwear performance was evident at the start of tire life. The low heat generation of the modified compound in laboratory tests is confirmed in actual tire testing. Advantages in rolling resistance characteristics are also evident for the modified compound. Current studies at MRPRA suggest that further modifications of cure system design, in combination with the optimization of NR/BR ratios and mixing methods, will potentially provide NR dominant truck tread compounds which will exhibit superior wear performance in both the higher and lower abrasion severities encountered in heavy-duty truck tire service conditions.
Criteria for Unstable Tearing of Elastomers
Authors: Stacer R. G. , Kelley F. N. 
Published: February 2011

Abstract
1. Unstable, or stick-slip, tearing has been evaluated in a series of unfilled elastomers. It was found that unstable tearing in these materials occurs only in well defined regions of temperature and rate. The behavior of the material in these regions follows a definite time-dependent pattern, suggesting the existence of simple time-temperature correspondence. This has been demonstrated by showing that the same shift factors that superpose other viscoelastic functions also describe the time-dependent nature of unstable tearing. Previous work showed that the magnitude of unstable tearing could be controlled by test-specimen geometry. It is concluded in this work that the mechanistic origin of unstable tearing can be traced to viscoelastic processes of the rubbery network. The combined results of these 2 studies show that unstable tearing is a characteristic feature of the polymer network which may be controlled or eliminated by test-specimen design. 2. For the amorphous elastomers investigated, it has been shown that the boundaries between regions of stable and unstable tearing can be explained in terms of simple extension properties and characteristic viscoelastic transitions of the elastomer. Specifically, the long-time (or high-temperature) boundary between conditions of stable and unstable tearing has been associated with a critical extension ratio, λc, which corresponds to an upturn in tensile stress-strain curves. If temperature and rate conditions are such that the deforming material at the tear tip does not extend beyond λc, unstable tearing does not occur. This is consistent with an anisotropic tear-tip reinforcement model of unstable tearing which has been discussed in detail. The short-time (or low-temperature) boundary between stable and unstable tearing conditions has been related to a characteristic time, ttr, associated with the onset of the rubber-to-glass transition. This characteristic time also corresponds to a change in the simple extension response of the elastomer. At times shorter than ttr, a distinct yield point was observed in constant rate stress-strain curves. It is therefore surmised that unstable tearing does not occur in this region due to the plastic yielding of the material, which interrupts the formation of the anisotropically reinforced structure at the tear tip. 3. Time-dependent tear-energy master curves of elastomers over broad time scales all display the same general features. Near the glassy region, the elastomers were found to approach a glassy tear energy of approximately 60 kJ/m2. At much longer times, in the terminal regions of the mastercurves, the tear energy dropped rapidly. In between these two extremes, a plateau was observed for all the elastomers, with NR displaying the lowest plateau slope.
Characteristics of a Series of Energy-Absorbing Polyurethane Elastomers
Authors: Mendelsohn Morris A. , Navish Francis W. , Kim Dongsik 
Published: February 2011

Abstract
Compositional effects were measured on a series of polyurethanes prepared by extending MDI-terminated PTMG prepolymers with dihydric alcohols and MCHDI-terminated prepolymers with diamines. The tensile and compressive stiffness and hysteretic loss increased while the resilience decreased with a decrease in the isocyanate equivalent weight of the prepolymer. Polyol chain extenders having an aromatic structure provided greater rigidity and increase in temperature on compressive cycling than did their aliphatic counterparts. Structural linearity and symmetry of both the aliphatic and aromatic extenders promoted greater rigidity and resiliency and less damping. Although direct replacement of MDI with MCHDI gives softer polyurethanes, use of the aromatic diamine extenders with the MCHDI-terminated prepolymers gave materials displaying the least resilience and greatest rigidity under static test conditions and the highest increase in temperature on compressive cycling. However, a significant increase in the chain length of the aromatic diamine-extended prepolymer provided properties quite similar to those obtained with the aliphatic diol systems.
Corona Discharge Activation and Reconstruction of Elastomer Surfaces
Authors: Lawson David F. 
Published: February 2011

Abstract
Corona discharge in air appreciably increased surface energies of ethylene—propylene—diene rubber (EPDM), a blend of chlorobutyl and natural rubbers, and styrene—butadiene rubber (SBR), as determined by contact angle measurements. High energy surfaces were typically short-lived, on the order of minutes, presumably due to facile reconstruction of the surface by mobile elastomer chains. Surface activation occurred despite the relatively thick specimens (1.8–2.5 mm) and the presence of up to 35% by weight of carbon black. Electrode configurations had an effect on the experimental results. Ozone, a byproduct of corona discharge, eroded the surface of SBR. Modest improvements in the bonding of an elastomeric urethane coating were realized with some of the surface-activated elastomers.
Rubber Flow in an Internal Mixer
Authors: Griffith R. M. , Kannabiran R. , Tomlinson G. S. 
Published: February 2011

Abstract
A number of experimental studies have improved understanding of rubber flow in internal mixers. Freakley and Van Idris obtained flow patterns and areas of fill by photographing through a transparent end plate of a small internal mixer during rubber mixing. White and Min obtained additional information by videotaping through transparent end plates and body sides of a small internal mixer during rubber mixing. Sata and associates used observations of flow of polymer solutions in a transparent Banbury mixer to help optimize rotor design. Freakley and Van Idris, Freakley and Patel, and Toki and associates used responses from pressure sensors installed in the body of Banbury mixers to infer the fill and flow directions during rubber mixing. Here we report findings based on direct examination of the contents of a Brabender mixer removed after curing in place so as to limit further flow after stopping mixing. The technique used is basically the same as that employed in the past to determine flow patterns in screw extruders. Melotto has also used this method without curing in work to optimize mixer geometry.
An Experimental and Theoretical Study of Heat Conduction and Vulcanization of Rubber Compounds in Molds
Authors: Kong Dancheng , White James L. , Weissert Frederick C. , Nakajima Nobuyuki 
Published: February 2011

Abstract
A fundamental study on curing of rubber compounds in molds is presented. We have measured the thermal conductivity of a range of rubber compounds determining the influence of carbon black, other fillers, and oil. The heats of reaction associated with the curing kinetics of model compounds were measured. A mathematical model is proposed to predict the temperature profiles for curing a reactive slab. This involves inclusion of an energy generation rate, which depends on time and temperature. This is expressed through a Damkohler number. Solutions of the heat conduction equation are interpreted in terms of the Fourier number and the Damkohler number. Calculations are carried out using experimentally determined thermal conductivities and curing kinetics. Thick parts are shown to heat up more slowly (associated with the Fourier number) and to show greater overshoots of cure temperature (associated with the Damkohler number).
Relationship between Molecular Structure and Mixing Mechanism
Authors: Shiga S. 
Published: February 2011

Abstract
The relationship between the molecular weight, the bound rubber, and the PI value was studied for EPR, of which the molecular structure was measured with GPC-LALLS. A strong linear correlation is found between the bound rubber and the PI value. The Meissner theorem, modified to express a severer dependence of the bound rubber on the molecular weight than the original theorem expects and the use of a molecular size instead of the molecular weight, can explain the relationship between the molecular weight and the bound rubber, accordingly the PI value. They indicate not only the dependence of mixing processability on polymer adsorption, but also strongly suggest the mechanism of carbon black dispersion that aggregates are scraped out from the surface of agglomerates as illustrated by the onion model. A pulsed NMR was used to measure the spin-spin relaxation time T2 of EPR in rubber compounds of different mixing time to study the rubber phase structure and its time change. It can be imagined from the T2-time curves that till tmin, polymer molecules are rapidly bound on the carbon black surface to become thick gradually, while adsorbed segments per a molecule increase with time. After tmin, gradual rearrangement of molecules on the surface and the biphasic structure of the bound rubber may proceed. The whole thickness of the bound rubber increases gradually even after tmin. The resistance against the dispersion of carbon black seems to be strengthened with mixing time.
A Theoretical-Experimental Method for Analyzing the Dynamic Behavior of Elastomeric Lip Seals
Authors: Prati Edzeario 
Published: February 2011

Abstract
An analytical-experimental method has been presented, which permits the dynamic behavior of lip seals for rotating shafts to be analyzed in the presence of both interference and static and dynamic eccentricities. A mathematical model which accounts for viscoelastic and inertial effects, permits determination of the lip—shaft contact conditions, the dynamic lip profile, and the gap area for various shaft speeds. The parameters which define the mathematical model have been determined experimentally. Such a model permits the performance of the particular seal studied to be predicted for various operating conditions. Finally, the influence of parameters characterizing the viscoelastic and inertial effects on the gap area have been examined. The analytical findings correlate well with the experimental measurements of fluid leakage for practically relevant values of the shaft angular velocity.