bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Rubberized Limestone Filler in Asphalt Paving Mixtures
Authors: Bissada Amir F. , Anani Ali A. 
Published: February 2011

Abstract
The method of direct dispersion of small amounts of rubber particles in asphalt binder was associated with difficulties in controlling degradation, mix uniformity, oxidation, and noxious fumes generated by grinding rubber. This study showed that asphalt cements can be modified by adding carboxylated butadiene rubber chemically bound to calcium carbonate to give a wide range of products of different compositions and consistencies. These rubberized fillers can disperse more rapidly in the hot asphalt during the mixing operation and require no adjustments or changes in conventional mixing practices. The conclusions that can be drawn from the experiments conducted include the following: 1. The relatively high stiffening effect of rubberized filler on the F/A binder system is related to its high surface activity or interfacial energy. Limiting values of viscosity increase in F/A binder systems were developed from the effective volume concentration values of rubberized filler to keep resistance to compaction of asphalt paving mixtures within desirable limits. 2. The surface of limestone filler chemically reacted with rubber is rendered more hydrophobic. This results in a pronounced reduction in the stripping of asphalt aggregate surfaces. For uncoated limestone filler, however, the stripping potential increased with the increase of immersion time in water. 3. Temperature susceptibility is decreased by adding rubberized limestone filler to asphalt. 4. Initially, the increase in the RL/L ratio of filler used in the sand-asphalt mixture causes an increase in Marshall stability. After a critical limit (corresponding to the critical effective volume concentration of the fillers in the F/A system), however, the stiffening offers significant resistance to compaction, causing the Marshall stability to decrease. 5. The addition of rubberized filler in RL/L ratios up to 40/60 by weight significantly improved the tensile strength properties of the sand-asphalt mixtures. 6. The values of retained tensile strength after different moisture conditioning methods indicate greater adhesion for mixtures containing rubberized filler up to a RL/L ratio of 40/60 by weight.
Elastomeric Tetramethylene-Ethylethylene-Acrylonitrile Copolymers
Authors: Weinstein A. H. 
Published: February 2011

Abstract
Elastomeric tetramethylene-ethylethylene-acrylonitrile (TEAN) copolymers were prepared by quantitative selective hydrogenation of emulsion NBR polymers in solution in presence of a triphenylphosphine-liganded rhodium salt catalyst. Completeness of hydrogenation at low pressure required appreciable excess of triphenylphosphine. Physical and chemical properties of TEAN gums of varying acrylonitrile segmer content, and their sulfur- and peroxide-cured vulcanizates are characterized. As expected, both gums and vulcanizates were very resistant to attack by oxygen. The exceptionally high tensile strengths of such vulcanizates were attributed to the crystallizability of the gums on stretching. Certain peroxide-cured TEAN vulcanizates prepared from green stocks containing magnesium oxide had a combination of resistance to heat aging in air, hydrogen sulfide, and oil, suggesting their applicability to well-drilling components.
Crosslinking of Halogen-Containing Rubbers with Triazine Dithiols
Authors: Mori Kunio , Nakamura Yoshiro 
Published: February 2011

Abstract
The crosslinking of various halogen-containing rubbers with triazine thiols and metal compounds was investigated, with the following conclusions: (1) Triazine thiols react with halogen-containing rubbers after reacting with metal compounds to form salts. (2) Reactivity of triazine thiols and metal compounds increased with a decrease in thiol pKa, and with an increase in the thiol anion basicity. (3) In this crosslinking, the reactivity of rubbers increased in the order: FR &lt; CPE &lt; PVC &lt; CIP &lt; CO &lt; ECO &lt; CAR &lt; CR. (4) In the crosslinking of CAR, the ether groups in a side chain activated the crosslink site. The sequence of oxyethlene units in ECO was found to activate the crosslinking agents. (5) The active halogen-containing rubbers such as CR and ECO were crosslinked by a combination of inactive F, MgO, and retarders such as Santogard PVI. (6) On the contrary, the crosslinking of rubbers containing inactive halogen, such as soft PVC and FR, was carried out by a combination of active DB, MgO, and accelerators such as polyethylene glycols or onium salts.
Temperature Effects on the Stability of Intermediates and Crosslinks in Sulfur Vulcanization
Authors: Morrison N. J. , Porter M. 
Published: February 2011

Abstract
The dependence of the physical properties of sulfur vulcanizates of diene rubbers on network structure is reviewed and the influence of degree of crosslinking, crosslink structure, and main-chain modification are discussed. In polyisoprenes, these are determined, in practice, by the balance between three competing types of reaction: the conversion of polysulfidic pendent groups into polysulfidic crosslinks; the desulfuration of polysulfidic pendent groups and crosslinks, eventually to the corresponding monosulfides, with recirculation of the removed sulfur into the crosslinking pathway; thermal decomposition of di- and polysulfidic pendent groups and crosslinks with the formation of cyclic sulfide, conjugated diene and triene, and cis, trans-isomerized groups in the rubber chains. At temperatures above about 160°C, the thermal breakdown of monosulfide crosslinks and pendent groups has to be considered. Zinc accelerator-thiolate complexes play a central role in controlling the balance between the various reactions because they promote the primary sulfuration of the rubber to form polysulfidic pendent groups and the conversion of these to crosslinks; they are the agents which desulfurate both pendent groups and crosslinks; they catalyze polysulfide exchange reactions; and in some cases they promote the decomposition of crosslinks. Other factors which affect the balance between these reactions are the temperature and the structure of the main rubber chain in the immediate vicinity of the crosslink. The latter is, in turn, at least partly controlled by the structure and concentration of zinc accelerator-thiolate complexes. The vulcanization of polybutadiene rubbers deviates substantially from this reaction pattern, evidently because the bulk of the accelerator becomes irreversibly bound to the rubber at an early stage. This denudes the vulcanizing system of zinc accelerator-thiolate complexes and, therefore, prevents desulfuration from occurring. The crosslinks thus remain di- and polysulfidic and are apparently less prone to decomposition than in the case of the polyisoprene rubbers, since cyclic sulfides and conjugated hydrocarbon groupings seem not to be prominent products. The removal of accelerator leaves the system unresponsive to zinc and gives it the characteristics of unaccelerated vulcanization with the result that vicinal crosslinking and crosslinks with saturated chain junctions become important products.
Stress Relaxation of NR and NBR: Comparison of Measured Data with Reduced Variables Estimates
Authors: Meier U. , Kuster J. , Mandell J. F. 
Published: February 2011

Abstract
The application of reduced variables has been tested in long-time compressive stress relaxation at 293 K over a time period of 16 years for NR and NBR. The results show that within this time span there is good agreement with predicted data from reduced variables. However, the results indicate that over much longer time periods (approx. 20 to 50 years) disagreement is to be expected due to dominance of chemical stress relaxation for surface to volume ratios in the range of 0.6/mm.
Zinc Oxide Crosslinking Chemistry of Halobutyl Elastomers—A Model Compound Approach
Authors: Vukov R. 
Published: February 2011

Abstract
The study of the crosslinking reactions of halobutyl rubbers with zinc oxide, conducted on low molecular weight model compounds, has brought about a thorough understanding of the chemistry of this process. It has been shown that there are two competitive processes taking place, with the major one generating the catalyst for the oligomerization reaction and producing a substantial amount of a monomeric diene. The actual crosslinking process is a cationically induced oligomerization based on carbon-carbon bond formation. The major high molecular weight product is the dimeric hydrocarbon with a small amount of trimeric product also being formed. Both the direct elimination reaction and the crosslinking process lead to the formation of dienic functional groups.
Plasticization of Nitrile Elastomers by in Situ Grafted Acrylate Monomers
Authors: Eldred Roger J. 
Published: February 2011

Abstract
Grafting of acrylate monomers, such as 2-ethylhexyl acrylate, onto nitrile rubber during the normal cure cycle of the elastomer led to a significant improvement in low-temperature flexibility. This method was shown to provide not only permanent plasticization, but also more than twice the effectiveness obtained by the simple addition of a polymeric acrylic plasticizer. It was found that the improvement in flexibility was directly proportional to the amount of monomer employed. The structure of the monomer was also important in determining its effectiveness, since variations in both the length and chemical composition of the ester side-chain led to changes in the low temperature properties. Improvements were obtained with longer side-chains, while the presence of oxygen in the side chain reduced the effectiveness compared to that of a pure hydrocarbon side-chain. Some slight effect of peroxide type used in the cure system was observed, but no differences in flexibility occurred with variations in cure temperatures between 163° and 204°C.
Acid-Base Contributions to Polymer-Filler Interactions
Authors: Fowkes Frederick M. 
Published: February 2011

Abstract
1. Acid-base interactions determine adsorption and bonding of polymers to fillers. 2. Quantitative predictability of the enthalpy of such bonding is attainable from the Drago C and E equation once the C and E constants are determined for polymers and fillers. 3. Infrared and calorimetric methods are discussed for determining the C and E constants for polymers and fillers. 4. For the case of poly(methylmethacrylate) filled with silica, the enthalpy of bonding has been determined by FTIR spectroscopy. 5. Acid-base interactions between polymers and fillers generate high zeta-potentials which tend to eliminate filler flocculation and reduce viscosity of filled polymer melts.
The Deresination of Guayule: A Physical Model. Part II: A Two-Component Analog for Deresination
Authors: Budiman S. , McIntyre D. 
Published: February 2011

Abstract
Based on GPC, the worm resin can be separated into two distinct groups, large and small. To obtain the overall diffusion coefficients for the two groups that could be useful as commercial design parameters, the worms were converted into wet worm crepe. Diffusion studies with model compounds, abietic acid, and trilinolein, reveal that: (a) their diffusion coefficients for desorption into acetone are inversely proportional to their respective molecular size, (b) the diffusion behavior of the two model compounds in a mixture can be fitted to a simple additive model, and (c) their diffusion coefficients are quite similar to those of the two groups of resin constituents (large and small). It is, therefore, possible to model and optimize a commercial deresination process for guayule worms on the basis of the diffusion behavior of two model compounds linolein and abietic acid and the physical geometry.
Low Modulus, High Damping, High Fatigue Life Elastomer Compounds for Vibration Isolation
Authors: Lemieux Marvin A. , Killgoar Paul C. 
Published: February 2011

Abstract
NR/BR/NIR copolymer blends were found to be too stiff at low temperatures for many potential isolation applications. Soft compounds have been developed which exhibit high damping, long fatigue life, and good heat resistant properties. These compounds are based on NR/BIIR blends with IM as a diluent. The new compounds are cured with a semi-EV cure system. The morphology appears to be an important factor controlling the fatigue properties of the blends. Fatigue life can be affected by the cure temperature, molecular weight of the IM used, and by the use of amine anti-oxidants. For improved processing and shelf-life stability, the use of amine anti-oxidants is not recommended.
The Chemistry of the Zinc Oxide Cure of Halobutyl
Authors: Kuntz I. , Zapp R. L. , Pancirov R. J. 
Published: February 2011

Abstract
The studies described in this papier lead to certain conclusions. The crosslinking reaction of halobutyl with zinc oxide does not give rise to ether crosslinks. All the evidence indicates that the chemistry involves the formation of carbon-carbon bonds by an alkylation type chemistry. The dehydrohalogenation of the halobutyl to form a zinc chloride catalyst is a key feature of the crosslinking chemistry. But conjugated diene butyl and Diels-Alder reactions are not the major reaction pathway for the zinc oxide crosslinking reaction. These conclusions have significance for the zinc oxide cure of CR which has an active allylic halide structure formed by 1,2-monomer enchainment.
Trowelable Rubber Rocket Insulation for Use at 2800°C
Authors: Sommer J. G. 
Published: February 2011

Abstract
Ablative, trowelable rocket insulation was prepared; it crosslinks at room temperature and self-bonds to prevulcanized NBR insulation. The material loss rate (MLR) of this insulation is low when it is tested by an oxyacetylene torch at temperatures of about 2800°C. Boric acid in the insulation causes an effective char to form at service temperature. This char slows the loss rate of nondegraded insulation beneath it. Density of this nondegraded insulation is 1.3 g/cm3. Density is reduced sharply to 0.8 g/cm3 by incorporating glass microballoons. They cause only a slight increase in MLR of the insulation at service temperatures. MLR can be significantly reduced by incorporating a blowing agent which decomposes only after the insulation is exposed to service temperature. Hence, an unusual combination of requirements is met by several novel approaches. This insulation has protected rockets as large as 6.6 meters in diameter from the intense heat of burning propellant in service.
Identification of Rubber Additives by Field Desorption and Fast Atom Bombardment Mass Spectroscopy
Authors: Lattimer Robert P. , Harris Robert E. , Ross Doyle B. , Diem Hugh E. 
Published: February 2011

Abstract
From the results presented here, it is clear that FD-MS and FAB-MS are very effective analytical methods for the identification of organic additives in extracts from rubber compounds. In the examples above, the molecular weight information provided by FD and FAB provided a nice complement to the IR data. In cases where IR could give only a general answer (i.e., a compound class), the mass spectral data provided a very specific compound identification. It is encouraging that all the samples examined gave useful spectra by both FD and FAB analysis. In most cases, the same information was obtained by both techniques. Certain compounds, however, were observed by FD but not by FAB (wax, oil, isocyanurate antioxidant). While FD provided only molecular weight information, FAB also provided fragmentation to aid in the confirmation of component assignments. Both the FD and FAB mass spectra were fairly complex for most of the extracts, but for different reasons. In FD, oil and wax oligomers gave many molecular ions over a wide mass range. FAB spectra, on the other hand, were somewhat cluttered due to the normal background ions produced by the sputtering process. With both techniques, however, the various components in some fairly complex mixtures were readily identified.
The Bonding of Polychloroprene to Brass: Rate and Temperature Effects
Authors: Hamed G. R. , Liu F-C. 
Published: February 2011

Abstract
The bonding of CR to brass shim has been studied at various test temperatures and rates using a T-peel geometry. Compounds without sulfur adhere relatively weakly to brass, and the bond strength is highly temperature dependent. The bonding strength is greatly enhanced, and its temperature dependence decreased, if the CR contains only a minute amount of sulfur. Adhesive joints made with rubber compositions containing just 0.5 phr or more of sulfur fail by cohesive tearing within the elastomeric layer, when tested at high temperatures; the bond strength thus exceeds the cohesive strength of the elastomer. At sufficiently low temperatures, the locus of fracture changes to the interfacial region. The temperature at which this transition occurs is independent of sulfur levels, suggesting that the bond strength is not very dependent on the sulfur level, at least for concentrations in the range of 0.5–9.0 phr. Unlike NR, which generally requires 3.0 phr or more of sulfur to obtain strong bonding, CR bonds tenaciously to brass when quite low levels of sulfur are present. Additionally, an ultra accelerator such as TMTM does not “destroy” the adhesion of CR to brass, as it does in the case of NR-brass bonding. This indicates that the sulfidation reaction at the interface between the rubber and brass is highly dependent on the chemical characteristics of the elastomer and not just the nature of the compounding ingredients.
Polybutadiene Vulcanization. Chemical Structures from Sulfur-Donor Vulcanization of an Accurate Model
Authors: Gregg Earl C. , Lattimer Robert P. 
Published: February 2011

Abstract
Only 1,5-polyenes with three or more double bonds crosslinked in a curing recipe with 2-benzothiazolyl-N-morpholyl disulfide (BMD) or bis(dimethylthiocarbamyl) disulfide (TMTD) as the crosslinking agents. A suitable chemical model for 1,4-polybutadiene (PB) is cycIohexadeca-1,5,9,13-tetraene (CHT). The preparation of CHT is described. The crosslink density of a CHT vulcanizate agreed well with the chemical crosslink density of cis- 1,4-polybutadiene rubber, similarly cured. The crosslink density of the CHT vulcanizate was measured by isolating, identifying, and weighing the various crosslink structures. The non-crosslink structures of the network and the extranetwork structures were also identified and quantified. Various amounts of curative fragments attach to the PB network structure, as exemplified by the amount of curative fragments attached to CHT. About 16% of the lauric acid attached to the network structure. The curing agent, BMD, divided into three fragments: 2-thiobenzothiazole, morpholyl, and thio groups. About 67% of the thio groups, 25% of the 2-thiobenzothiazole groups, and about 6% of the morpholyl groups attached to the network structure. About 57% of the thio groups formed crosslinks. The main crosslink structure was 85% bis(allylic) monosulfide and 15% bis(allylic) disulfide. The length of the disulfide crosslink was only 60 pm greater than the length of the monosulfide crosslink. This compares with the 0.2 nm length of a sulfur atom. Very little cis-trans isomerization occurred in the unreacted CHT as a result of vulcanization. This indicated almost no cis-trans isomerization of unreacted segments of PB in PB vulcanizates. However, extensive cis-trans isomerization occurred in the CHT that crosslinked, which indicates that cis-trans isomerization in PB vulcanizates is confined to the reaction sites of the PB molecules. The configurational isomerism was essentially exclusively cis-to-trans. No trans-to-cis isomerism was observed. The insoluble solid in the vulcanizate was a mixture of cadmium bis(2-thiobenzothiazole), cadmium sulfide, and morpholinium sulfate. Material balances of the reaction products with the curatives showed that 90% by weight of the reaction products of the vulcanization of CHT were identified. The hydrogen transfer balance showed that CHT is the main hydrogen donor during crosslink formation. The morpholyl group from BMD was the main hydrogen acceptor and formed morpholine and morpholinium sulfate. Escape of volatile substances during vulcanization of PB resulted in much reduced crosslinking. For this reason, a hydraulic reactor for vulcanization of liquids, such as CHT, without loss of volatile substances was described.
Effects of Compound Formulation on the Adhesion of Rubber to Brass-Plated Steel Cord
Authors: Ishikawa Yasuhiro 
Published: February 2011

Abstract
Implications for cord adhesion from this study are as follows: 1) In the low-adhesion compounds containing low cobalt naphthenate and sulfur levels, adhesion increases with decreasing cobalt naphthenate:sulfur ratio, at a given amount of cobalt naphthenate. 2) Under mild curing condition (160°C, 20 min), high-adhesion compounds, containing high cobalt naphthenate and sulfur level, do not show a decrease in adhesion, even if the cobalt naphthenate:sulfur ratio is increased. However, after overcuring (160°C, 60 min), adhesion loss is encountered with increasing cobalt naphthenate:sulfur ratios, at a given cobalt naphthenate level. 3) A high level of unaged adhesion can be obtained if products with a combination of low cobalt and high sulfur content are formed on the brass surface. This condition obtains if the compound contains large amounts of cobalt salt and sulfur and a small ratio of cobalt salt to sulfur. 4) With a high-adhesion compound, the unaged adhesion is rather insensitive to the amount of accelerator. 5) After humidity aging, the adhesion of a high-adhesion compound varies depending upon the amounts of sulfur and accelerator. Compounds containing small amounts of sulfur show a decrease in adhesion with increasing amounts of the accelerator. However, compounds containing large amounts of sulfur maintain high adhesion, even with large amounts of accelerator. 6) For unaged adhesion, only a slight influence is observed by varying the amount of stearic acid. After humidity aging, however, compounds containing larger amounts of stearic acid show a decrease in adhesion, especially in the presence of large amounts of cobalt naphthenate. 7) Compounds which promote the formation of ZnO on the surface during bonding maintain a high adhesion level after humidity aging. This is similar to the effect of using a cord plated with brass containing a higher zinc level.