bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Polymer-Filler and Filler-Filler Interactions on Dynamic Properties of Filled Vulcanizates
Authors: Wang Meng-Jiao 
Published: February 2011

Abstract
In the past few years, an enormous amount of work has been reported on the progress in the application of conventional fillers and the development of new products to improve the reinforcement of rubber, dynamic properties in particular. While all agree that the filler as one of the main components of the filled-rubber composite, has a very important role in improving the dynamic performances of the rubber products; many new ideas, theories, practices, phenomena, and observations about how and especially why the filler alters the dynamic stress-strain response have been presented. This, of course, suggests that not only is the real world of the filled rubber complex and sophisticated but also multiple mechanisms may be involved. However, it must be admitted that the possibility exists for explaining the effect of all fillers on rubber properties ultimately in similar and relatively nonspecific terms, i.e., the phenomenon related to all filler parameters should follow a general rule or principle. It is the author's belief that, with regard to the effect of filler on the dynamic properties of a given polymer and cure system, filler networking, both its architecture and strength, is the main (although not only) parameter to govern the behavior of the filled rubber. From the thermodynamic and kinetic points of view, filler network formation is especially related to filler-filler, polymer-filler, as well as polymer-polymer interactions. As mentioned in the introduction, this paper is an attempt to review the effect of filler characteristics on dynamic properties in connection with processing conditions and additives. Since the polymer-filler interaction is not only affected by filler, what is also important are the characteristics of polymers such as chemical composition, chain microstructure including molecular weight and molecular weight distribution, configuration, stereoregularity, monomer unit distribution and sequence, and their functionality. All of these have a substantial influence on the physical and/or chemical interactions with other additives and filler surfaces, as well as on the interaction between polymer molecules themselves, which would impact not only the filler network formation but also the viscoelastic response of the polymer matrix. In addition, the polymer network structure which was formed during vulcanization and characterized by crosslink density, crosslink structure, and chain modification, is equally important in contributing to the overall dynamic properties of the filled rubber. In this paper, only some of these aspects have been discussed relative to their effect on filler network formation. Further discussion of these parameters is beyond the subject of the present paper. However, some guidance to these important topics is given in a handbook that was recently published.
Crystallization and Strength of Natural Rubber and Synthetic cis-1,4-Polyisoprene
Authors: Gent A. N. , Kawahara S. , Zhao J. 
Published: February 2011

Abstract
Crosslinked samples of natural rubber (NR, SMR-5L) and a synthetic cis-1,4-polyisoprene (IR, Natsyn 2200, The Goodyear Tire & Rubber Company) were crystallized at −25 °C at various strains, and then slowly melted. Crystallization was somewhat slower for IR under all conditions, taking two to three times as long as for NR crosslinked to the same degree. The melting temperature was also a few degrees lower. These effects are consistent with the presence of a small fraction of non-cis material in the IR molecule. Measurements of tensile strength and tear strength were made over a wide temperature range. The results were closely similar for the two materials at low rates of stretching although the abrupt fall in tensile strength associated with a failure to crystallize occurred at slightly lower temperatures for IR. Tear strength at low speeds showed a steady fall on raising the temperature, with little difference between the two materials. However, at high rates of strain the IR materials appeared to have significantly lower tensile strength, and at high tear speeds the tear strength was markedly lower, about one-half of that for NR. Thus, the minor structural irregularities in IR appear to be of little consequence at low rates of strain, but cause significant weakening at high rates, when the lower rate of crystallization is inferred to become a critical factor.
Homogeneous Zinc(II) Catalysis in Accelerated Vulcanization I. Reaction-Stage Modeling and Cross-Link Formation
Authors: Nieuwenhuizen Peter J. , Timal Sandjai , van Veen Jeroen M. , Haasnoot Jaap G. , Reedijk Jan 
Published: February 2011

Abstract
This paper reports a novel approach for the study of the mechanism of accelerated vulcanization, namely, Reaction-Stage Modeling (RSM). By carefully studying the reactivity of relevant model compounds under selected conditions, detailed knowledge about a particular reaction stage of vulcanization can be obtained. Background, experimental details and synthesis of model compounds are described. An RSM study after cross-link formation in the thiuram- and dithiocarbamate type vulcanization has been performed, and the role of zinc compounds herein was investigated. In contrast to earlier studies, it has appeared that at 140 °C, cross-links form from cross-link precursors solely via disproportionation. Allylic substitution was not observed. Zinc compounds act as catalysts for disproportionation, but especially ZDMC can be regarded as an efficient, soluble molecular turntable for sulfur atoms.
High Flow TPO Compounds Containing Branched EPDM Modifiers
Authors: Dharmarajan N. , Kaufman L. G. 
Published: February 2011

Abstract
Polymer blends of ethylene-propylene elastomers and polypropylene plastics, referred to as thermoplastic olefins, are finding increasing use in automotive applications. The combination of attractive mechanical properties, low raw material cost and recyclability make these materials ideal substitutes for expensive engineering thermoplastics (polycarbonate/polybutylene terephthalate alloys) and nonrecyclable polyurethane systems. The primary application is in automotive bumper fascia. This paper describes the addition of long chain branched ethylene-propylene elastomers in thermoplastic olefin compounds containing a high flow polypropylene resin matrix. In such compounds, the modifier molecular architecture plays an important role in impact toughening. The results clearly indicate that linear modifiers such as traditional ethylene-propylene copolymers are ineffective in impact toughening, while long chain branched polymers provide enhanced impact resistance with a ductile failure mode in high flow polypropylenes.
Characterization and Physical Properties of New Isobutylene-Based Graft Copolymers
Authors: Tse Mun F. , Dias A. J. , Wang H-C. 
Published: February 2011

Abstract
A number of isobutylene-based graft copolymers with different compositions are compared to several commercial thermoplastic block copolymers, such as SIS, SBS and SEBS, in terms of morphology and viscoelasticity. The backbone of these graft copolymers is a terpolymer (BIMS) of isobutylene, p-methylstyrene and p-bromomethylstyrene, and the side chains are either polystyrene or poly(2,6-dimethyl-1,4-phenylene ether). Graft copolymer synthesis, statistics of graft formation, and stress-strain properties are described. Overall, these graft copolymers exhibit unique shear dependent viscosity effects, such as rapid thickening (quick setting) at low shear and lower viscosity (better processability) at high shear, compared to linear triblock copolymers. The rheological behavior of these graft copolymers could be a key advantage for high-shear calendering, extrusion, hot-melt spraying, and injection molding.
Tensile and Tear Behavior of Anisotropic Double Networks of a Black-Filled Natural Rubber Vulcanizate
Authors: Hamed G. R. , Huang M. Y. 
Published: February 2011

Abstract
Double networks of a black-filled natural rubber composition have been prepared by partially curing a sheet, stretching it, and then completing cure. Upon release, a double network retracts to a residual extension ratio, αr. Samples cut perpendicular to the stretch direction have stress—strain responses like the isotropic single network, while parallel samples have enhanced stiffness and tensile strength, and reduced extensibility. Tensile strength is rather weakly dependent on αr. Tear strengths of the double networks, determined using edge-cut strip specimens, exceed that of the single network for low αr. However, when αr is high, double networks have very low tear strengths. Consistent with previous studies, high tear strengths are associated with extensive longitudinal cracking.
Fatigue of Cord—Rubber Composites: II. Strain-Based Failure Criteria
Authors: Lee B. L. , Ku B. H. , Liu D. S. , Hippo P. K. 
Published: February 2011

Abstract
Fatigue failure mechanisms under low-frequency loading and their dependence on the strain properties were assessed for the rubber matrix composite of bias aircraft tire carcass reinforced by nylon cords as well as two model rubber composites reinforced by steel wire cables. Under cyclic tension at constant stress amplitude, these angle-plied, cord—rubber composite laminates exhibited localized damage in the form of cord—matrix debonding, matrix cracking, and delamination. The process of fatigue damage accumulation in the cord—rubber composite laminate was accompanied by a steady increase of cyclic strain (dynamic creep) and moderate temperature changes. The fatigue life was found to be linearly proportional to the inverse of the dynamic creep rate, i.e., the time required to increase cyclic strain by a unit amount. Regardless of the associated level of stress amplitude or fatigue life, the gross failure under low-frequency loading occurred when the total strain accumulation, i.e., cumulative creep strain, reached the static failure strain. The use of higher stress amplitude resulted in a decrease of fatigue life by simply shortening the time to reach the critical level of strain for gross failure. This observation indicates that the damage initiation and eventual structural failure of angle-plied, cord—rubber composite laminates are “ strain-controlled” processes. These critical strain properties appear to be controlled by the process of interfacial failure between the cord and matrix. Under static tension, the strain levels for cord—matrix debonding and gross failure of composite laminates showed no significant dependence on the level of carbon black loading of the matrix compound, despite the fact that carbon black loading strongly affected the modulus, strength and strain properties of the matrix. Also the number of debonding sites around the cut ends of cords increased at almost the same rate as the static strain increased regardless of the variation of matrix properties.
Poly(Dimethylsiloxane) Elastomers from Aqueous Emulsions: I. Preparations, and Characterization of the Curing and Aging Processes
Authors: McCarthy D. W. , Mark J. E. 
Published: February 2011

Abstract
Poly(dimethylsiloxane) (PDMS) elastomers were prepared from aqueous emulsions, in combination with one of several carefully chosen alkoxy silanes as a crosslinking agent, and either stannous-2-ethylhexanoate or dioctylitin dilaurate as catalyst. Conditions were generally chosen so as to generate silica/silicate phases within the elastomeric particles or at their surfaces, for improvements in mechanical properties of films to be cast from the emulsions. A series of such films was obtained from emulsions consisting of various combinations of these ingredients, and was then characterized, primarily by measurements of soluble fractions, and by extents of equilibrium swelling (as inverse measures of degrees of crosslinking). Of primary interest were experimental results clarifying the mechanisms for the PDMS crosslinking and for the subsequent “aging” of these materials. For all the systems, increase in concentration of crosslinking agent was found to decrease the fraction of soluble polymer present and to decrease the extent of swelling. The extent to which this occurred, however, varied significantly with the nature of the alkoxy silane crosslinking agent, its concentration, and the nature of the catalyst. The observed differences were used to propose mechanisms with regard to the role of the silanes in the formation of silica-like phases, as well as for the endlinking of the PDMS chains. The formation of this inorganic phase was found to have a large effect on the extraction and swelling results, particularly through its barrier effects on the surfaces of the emulsion particles. Aging effects were found to depend not only on the nature of the reactants and their concentrations in the preparation of the emulsions, but also on whether the aging had been carried out in the dry state or in the wet state. Two major effects were decreases in soluble polymer fraction and extent of swelling with time. These changes were associated with increases in degree of crosslinking, but opposing changes can arise from bond cleavages or reorganizations. It appeared that dry-state aging effects are greatest for systems with a low concentration of the precipitated inorganic phase, with the effects of aging being suppressed by the presence of the inorganic, filler-like phases.
Poly(Dimethylsiloxane) Elastomers from Aqueous Emulsions: III. Effects of Blended Silica Fillers and γ-Radiation-Induced Crosslinking
Authors: McCarthy D. W. , Mark J. E. 
Published: February 2011

Abstract
The morphologies of the reinforced elastomers prepared from emulsions were found to depend greatly on how the silica phases were introduced. More specifically, blending colloidal silica into the elastomer prior to film formation was found to yield a highly unusual elastomer in which the continuous phase was the silica and the dispersed phase the elastomer. This is the opposite of the usual case in which, for example, the silica is generated in-situ within the continuous elastomeric phase. These morphological differences were used to explain the different shapes of the stress—strain isotherms of these materials in simple elongation. Results on the crosslinking effects of gamma radiation demonstrated that this treatment represents another useful technique for optimizing the properties of these emulsion-derived materials.
Synthesis, Characterization, Physical and Processing Properties of New TPEs: Star-Blocks Comprising Multiple Polystyrene-b-Polyisobutylene Arms Radiating from a Polydivinylbenzene Core
Authors: Asthana Siddhartha , Majoros Istvan , Kennedy Joseph P. 
Published: February 2011

Abstract
The synthesis of the title star-block thermoplastic elastomers (TPEs) was accomplished by linking living polystyrene-b-polyisobutylene (PSt-b-PIB⊕) diblocks with divinylbenzene. Linking was fast and high yields of star-block polymers were obtained. The products were characterized by a variety of techniques. The physical and processing properties of the star-blocks have been investigated and they were found to exhibit superior tensile properties and lower melt viscosities to those of similar linear triblock copolymers.
Crosslink Density Distributions in NR/BR Blends: Effect of Cure Temperature and Time
Authors: Groves Sally A. 
Published: February 2011

Abstract
Crosslink distributions in gum natural rubber (NR)/cis-poly(butadiene) (BR) blend vulcanizates have been studied previously for cure states ranging from times shortly after the onset of cure to over-cure at 150 and 175 °C, respectively. The effects of lower cure temperatures on the crosslink distributions through the cure in NR/BR blend vulcanizates are considered here. The results of this and the previous work indicate that at temperatures above 140 °C the BR phase in gum NR/BR blends begins curing before and at a faster initial rate than the NR phase. Below 140 °C it is the NR phase which attains high crosslink densities first and maintains this increased level over BR until over-cure. The effect of cure temperature on crosslink distribution at maximum state of cure is also presented.
Particle Size Distribution of Carbon Blacks by Mercury Porosimetry
Authors: Leon y Leon Carlos A. 
Published: February 2011

Abstract
Carbon blacks are made up of near-spherical elementary colloidal particles chained together in small clusters known as aggregates. These unique morphological characteristics have complicated their particle size characterization by conventional techniques. In this study the potential of mercury porosimetry for the generation of primary particle size distributions (PPSD) of carbon blacks is investigated. Two literature theories (Mayer—Stowe and Smith—Stermer) were applied to derive PPSD curves from mercury porosimetry analyses of six ASTM standard reference blacks (series SRB A5-F5) covering a wide range of particle sizes. Good agreement was found between particle sizes expected from electron microscopy and those determined by mercury porosimetry. The advantages of the latter technique for the routine evaluation of continuous PPSD curves are discussed.
Friction of a Rubber Wedge Sliding on Glass
Authors: Extrand C. W. , Gent A. N. , Kaang S. Y. 
Published: February 2011

Abstract
The contact width, and hence contact area, for an elastic wedge pressed against a rigid flat surface appears to be proportional to the applied load per unit length. For a particular rubber sample, the reciprocal of the constant of proportionality, i.e., the mean normal pressure, was 130 kPa, i.e., about 7% of the tensile modulus E of the material. It was also independent of sliding speed over the range examined. Thus, a sharp wedge gave a relatively high loading pressure, independent of the applied load. As a result, the coefficient of friction was also independent of applied load over a wide range. The coefficient of friction was measured for a wedge of an unfilled natural rubber vulcanizate over wide ranges of sliding speed (50 µm/s to 100 mm/s) and test temperature (3°C to 63°C). It was found to increase with sliding speed and decrease with temperature over these ranges. The results at different temperatures were superposable using the WLF rate-temperature equivalence to create a master curve of friction vs. reduced sliding speed, rising from a value of about 1.5 at high temperatures and low speeds to about 5 at low temperatures and high speeds. Chlorination of a thin surface region reduced the coefficient of friction and its dependence on speed and temperature. It then became similar to that typically found for thermoplastics, 0.4 to 0.7. The geometry of sliding a flexible strip against a rigid curved surface caused high values of the apparent coefficient of friction to be obtained at relatively small departures from normal loading. In an extreme case, frictional seizure was observed when a high-friction sample contacted the glass surface at an angle of about 15° to the direction of loading. The apparent coefficient of friction then became indefinitely large. This same phenomenon of abnormally large frictional effects would be expected to occur in the case of conventional windshield-wiper blades, sliding over curved glass windshields.
Solid-State Carbon-13 Studies of Vulcanized Elastomers. VIII. Accelerated Sulfur-Vulcanized Butyl Rubber at 75.5 MHz
Authors: Krejsa M. R. , Koenig J. L. 
Published: February 2011

Abstract
The chemical microstructural changes of an accelerated sulfur cure of IIR with TMTD/ ZnO/sulfur have been elucidated. No reaction occurs in the isobutylene units. Isomerization occurs at the initial stages of vulcanization and reaches an equilibrium at 30–35 min. Sulfurization initially results in III and VI and is polysulfidic in nature. At cure times greater than 75 min, desulfurization of III and VI occurs and mono- and poly-sulfidic sulfurization giving IV and VII occurs. The reaction rate of III and VI is much greater than that of IV and VII. Equilibrium swelling measurements have been shown to correlate with rheometry measurements for this system and have shown that polysulfldic III and VI correlate with an increase in properties, while mono- and poly-sulfldic IV and VII correlate with reversion. No migration of the double bond, saturation, internal cyclization, or sulfurization resulting in V and VIII were observed.
Effect of Temperature and Oxygen on the Strength of Elastomers
Authors: Gent A. N. , Liu Ginger L. , Sueyasu T. 
Published: February 2011

Abstract
1. A linear relationship has been found to hold for SBR vulcanizates between the logarithm of the rate of steady tearing and the logarithm of air pressure, over the range 10 Pa to 100 kPa. The slope varied from 0.08 for a C-C crosslinked material to 0.18 for a polysulfide-crosslinked material. Similar effects of air pressure were found in the rate of crack propagation under intermittent loading. They are attributed to attack of oxygen (in air) on highly stressed bonds, either sulfidic or hydrocarbon. 2. Approximately linear relationships were found to hold between the logarithm of the rate of steady tearing and the reciprocal of test temperature for temperatures between 25°C and 130°C. Apparent activation energies were deduced from the slopes, of 135 kJ/mole for a polysulfide-crosslinked SBR compound, 105 kJ/mole for a C-C crosslinked SBR compound, and 85 kJ/mole for a sulfur vulcanizate of BR. For SBR, these values were independent of air pressure. 3. These activation energies are far too large to be accounted for by changes in segmental mobility (and hence in internal energy dissipation) with temperature, for simple viscoelastic materials at temperatures far above Tg. The discrepancies are attributed to a second temperature-dependent factor. It is suggested that the threshold tear strength T0, i.e., the strength under nondissipative conditions, is itself temperature dependent. 4. Estimates of the changes in T0 with temperature have been obtained from the observed discrepancies in temperature dependence of tear strength. They correspond to a decrease from about 100–250 J/m2 at 25°C to about 50 J/m2 at 130°C. These changes in T0 may reflect the stress-activated rupture of thermally-sensitive bonds.
New Metallic Coagents for Curing Elastomers
Authors: Costin Richard , Nagel Walter , Ekwall Raymond 
Published: February 2011

Abstract
Based on the data reported in this paper, it is evident that the zinc salts of acrylic acid and methacrylic acid are effective coagents for the peroxide curing of EPDM and NBR. They appear to be unique among coagents in their ability to maintain high elongation while increasing the hardness and tensile properties of these elastomers. Zinc diacrylate was found to be the most effective in providing high hardness and high tensile properties. Zinc dimethacrylate gave a slightly better balance of properties by providing the highest elongation for a given hardness or modulus value.
Chemical Reactions of an Epoxy-Functional Silane in Aqueous Solutions
Authors: Xue Gi , Koenig Jack L. , Ishida Hatsuo , Wheeler Don D. 
Published: February 2011

Abstract
When the coupling agent is dissolved homogeneously in water, the hydrolysis rate of the alkoxy group is influenced by the pH of the solution, the size of the alkoxy group, and to a lesser extent, the size of the organofunctional group directly attached to the silane atom. We have quantitatively studied the reactions of γ-GPS in aqueous solutions. In a dilute solution, the silanol group slowly condensed to siloxane at pH = 4. The epoxy group reacts with both water and the silanol group. The reaction rate of the epoxy group with water is influenced by the pH of the solution. The reaction of the epoxy group with water proceeds faster than with the silanol group due to the large excess of water present, although the rate constants of these two reactions are comparable.