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1
Maciejewska, Magdalena, Anna Sowińska, and Judyta Kucharska. "Organic Zinc Salts as Pro-Ecological Activators for Sulfur Vulcanization of Styrene–Butadiene Rubber." Polymers 11, no. 10 (October 21, 2019): 1723. http://dx.doi.org/10.3390/polym11101723.
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Organic zinc salts and complexes were applied as activators for sulfur vulcanization of styrene–butadiene elastomer (SBR) in order to reduce the content of zinc ions in rubber compounds as compared with conventionally used zinc oxide. In this article, the effects of different organic zinc activators on the curing characteristics, crosslink densities, and mechanical properties of SBR as well as the aging resistance and thermal behavior of vulcanizates are discussed. Organic zinc salts seem to be good substitutes for zinc oxide as activators for sulfur vulcanization of SBR rubber, without detrimental effects to the vulcanization time and temperature. Moreover, vulcanizates containing organic zinc salts exhibit higher tensile strength and better damping properties than vulcanizate crosslinked with zinc oxide. The application of organic zinc activators allows the amount of zinc ions in SBR compounds to be reduced by 70–90 wt % compared to vulcanizate with zinc oxide. This is very important for ecological reasons, since zinc oxide is classified as being toxic to aquatic species.
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Koenig, Jack L. "Spectroscopic Characterization of the Molecular Structure of Elastomeric Networks." Rubber Chemistry and Technology 73, no. 3 (July 1, 2000): 385–404. http://dx.doi.org/10.5254/1.3547598.
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Abstract In vulcanization, chemical crosslinks are formed across elastomeric polymer chains improving both the strength and elastic properties of the rubber. An understanding of the formation, structure, and stability of vulcanizates is therefore very important. Solid-state NMR and NMR imaging have been effective methods to study many different aspects of vulcanization. In solid-state NMR, several peaks appear in the C-13 spectrum of vulcanized rubber. Through model studies, NMR analysis, and chemical shift additivity calculations, these peaks were assigned to their respective vulcanizate structures. Once this assignment was made, the concentration of each vulcanizate structure formed could be followed with time under a variety of different conditions. In unaccelerated sulfur vulcanization of natural rubber (NR) and polybutadiene rubber (BR), many inefficient (cyclic or intramolecular) structures were formed as compared to intermolecular crosslinks. In accelerated NR and BR sulfur vulcanization, NMR was used to study vulcanizate concentration dependence on (a) type of formulation (efficient, semi-efficient, or conventional), (b) type of accelerator, (c) extent of cure, and (d) different concentration of ingredients (sulfur, activator, etc.). Solid-state NMR was also used to study different parameters in butyl rubber and to identify elastomers in binary blends of chloroprene rubber (CR) and NR, CR and chlorosulfonated polyethylene (CSM), NR and CSM, and styrene—butadiene rubber (SBR) and acrylonitrile—butadiene rubber (NBR) as well as the tertiary blend of NR/SBR/BR. In several studies, the effect of filler (carbon black or silica) on vulcanization was studied. Additionally, the thermo-oxidative degradation of sulfur vulcanizates in NR with heating time and temperature was observed using NMR. NMR imaging has been useful in the determination of internal inhomogeneities arising from inadequate mixing, gradients in crosslinking chemistry, filler distribution, blends, and coagents.
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Menon, A. R. R. "Flame-Retardant Characteristics of Natural Rubber Modified with a Bromo Derivative of Phosphorylated Cashew Nut Shell Liquid." Journal of Fire Sciences 15, no. 1 (January 1997): 3–13. http://dx.doi.org/10.1177/073490419701500101.
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Natural rubber (NR) in a typical semi-efficient vulcanization system was modified with flame-retardant additives such as bromo derivative of phosphorylated cashew nut shell liquid, antimony trioxide and alumina tri hydrate (ATH). Improvement in the flame retardancy of the vulcanizates was shown by the progressive increase in Limiting Oxygen Index with the concen tration of ATH. Besides, the smoke density and the smoke release rate were reduced substantially in the presence of 100 phr of ATH in the vulcanizate. Thermogravimetric analysis showed higher activation energy for decomposi tion and higher yields of decomposition residue for the ATH-filled NR vulcanizates. Also, the vulcanizate modified with the flame retardants showed improvements in tensile and tear strengths in presence of 50 phr of the filler.
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Wang, Jingyi, and Hongbing Jia. "The Effects of Carbon–Silica Dual-Phase Filler on the Crosslink Structure of Natural Rubber." Polymers 14, no. 18 (September 18, 2022): 3897. http://dx.doi.org/10.3390/polym14183897.
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Carbon–silica dual-phase filler (CSDPF)/natural rubber (NR) vulcanizate was prepared by mechanical blending, followed by a hot-press vulcanization. The dispersion of CSDPF in the NR matrix and the effects of CSDPF on the filler–rubber interaction and structure of the rubber network were studied. Scanning electron microscope results showed that CSDPF dispersed uniformly; however, there were some aggregates of CSDPF when loading too many fillers. With an increase in CSDPF, the interaction between CSDPF and NR chains increases, which was detected by bound rubber in the CSDPF/NR compound. The spectra of solid-state nuclear magnetic resonance revealed that CSDPF could promote the formation of poly-sulfidic crosslink in the rubber vulcanization network. Further, the molecular chain movement ability of vulcanizates decreases according to the spin–spin relaxation of 1H nuclei in CSDPF/NR compounds. The crosslink density of vulcanizate increases, while the chemical crosslink and physical crosslink in the vulcanization network also increase according to the tube model.
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Mori, Kunio, Kentaro Kanae, Hidetoshi Hirahara, and Yoshiyuki Oishi. "Formation of Surface Structure in Vulcanizates and Surface Structure Changes in Air." Rubber Chemistry and Technology 68, no. 1 (March 1, 1995): 97–109. http://dx.doi.org/10.5254/1.3538734.
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Abstract The formation theory of surface structure during vulcanization was developed on the basis of an interfacial concept. The theory showed the chemical compositions of polar and nonpolar components on the vulcanizate surface to be determined as an excess interfacial free energy between rubber compounds and molds decreases. The surface free energies of molds reflected clearly the corresponding surface free energy of vulcanizates prepared from copolymers and polar polymers. Nonpolar polymers were not influenced by the surface free energies of molds. The surface free energies of vulcanizates decreased slightly with the concentration of network chains owing to the entropy of rubber segments. The surface free energies of molds affected the chemical compositions at the topmost surface region to the upper surface region on vulcanizates. NBR vulcanizates with high surface free energy increased the contact angle of water after standing in dry air. In the dry air environment, topmost surface layer nitrile groups were buried in the bulk of NBR vulcanizates and butadiene units subsequently overturn to the topmost, layer. In this case, the vulcanizate surface chemical composition was influenced only at the topmost surface region. ESCA spectra N1s peak intensities on NBR vulcanizates was consistent with these observation.
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Dikland, H. G., T. Ruardy, L. van der Does, and A. Bantjes. "New Coagents in Peroxide Vulcanization of EPM." Rubber Chemistry and Technology 66, no. 5 (November 1, 1993): 693–711. http://dx.doi.org/10.5254/1.3538338.
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Abstract 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.
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Hayeemasae, Nabil, Kamaruddin Waesateh, Siriwat Soontaranon, and Abdulhakim Masa. "EFFECT OF VULCANIZATION SYSTEMS AND CROSSLINK DENSITY ON TENSILE PROPERTIES AND NETWORK STRUCTURES OF NATURAL RUBBER." Jurnal Teknologi 84, no. 6 (October 3, 2022): 181–87. http://dx.doi.org/10.11113/jurnalteknologi.v84.16467.
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The mechanical properties of natural rubber (NR) vulcanizate depend strongly on several factors, i.e., vulcanization systems and crosslink density. These two parameters are originally from the formulation design of the vulcanizate. To focus more on such details, influences of three different vulcanization systems (sulfur, peroxide, and phenolic resin) with variations in their crosslink densities were studied by focusing on the change of curing properties, crosslink densities, mechanical properties and network structures of the NR vulcanizates. The crosslink density of various vulcanization systems increased with increasing curing promotors, as revealed by temperature scanning stress relaxation measurement. The tensile modulus at 100% strain increased with increasing crosslink density in all systems but the tensile strength varied with the vulcanization systems and degree of crosslink density. At the same crosslink level, the greatest tensile strength was obtained when the sulfur was used as a crosslinker, which was 100% greater than those obtained from peroxide and 200% over phenolic systems. In comparison to the phenolic resin system, sulfur and peroxide crosslink systems had a more uniform distribution of the crosslink network structure. The size of the network structure was found to be independent of the tensile strength. The peroxide system had the most uniform distribution of the crosslink network structure.
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Joseph, Anu Mary, Benny George, K. N. Madhusoodanan, and Rosamma Alex. "CURE CHARACTERISTICS OF DEVULCANIZED RUBBER:THE ISSUE OF LOW SCORCH." Rubber Chemistry and Technology 90, no. 3 (July 1, 2017): 536–49. http://dx.doi.org/10.5254/rct.17.83737.
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ABSTRACT We investigate the reasons behind the observed low scorch during the revulcanization of devulcanized rubber. Mechanically devulcanized carbon black filled natural rubber vulcanizates originally cured by conventional vulcanization (CV), semiefficient vulcanization (semi EV), efficient vulcanization (EV), and peroxide systems as well as buffing dust obtained from pre-cured tread with known formulation were used. Revulcanization of these devulcanized samples using sulfur/sulfonamide system led to the following observations; irrespective of the type of sulfur cure system used for the initial vulcanization of the rubber, (i) the devulcanized samples cured without pre-vulcanization induction time and (ii) devulcanized samples prepared from peroxide vulcanized rubber cured with scorch safety. Based on the earlier reports that solvent extraction of devulcanized rubber did not improve the scorch time during revulcanization, the role of zinc bound non-extractable moieties was investigated using devulcanized rubber prepared from activator-free vulcanizates, which disproved the role of such moieties. This confirmed that the scorch reducing moieties should be attached to the rubber main chain, which can be unreacted crosslink precursors and cyclic sulfides left after the initial accelerated sulfur vulcanization of the original sample. The ability of pre-vulcanization inhibitor to induce scorch safety when devulcanized rubber is revulcanized as such, without adding any virgin rubber, proved that mercaptobenzothiazole (MBT) generated from crosslink precursors is the cause of low scorch. Acetone extracted devulcanized rubber samples prepared from tetramethyl thiuramdisulfide (TMTD) cured natural rubber, which does not follow the MBT pathway when revulcanized, cured with scorch safety, which further proved the role of MBT. Based on the previous reports and our results, it is obvious that powdering of rubber vulcanizate and devulcanization processes have no role on the low process safety of these materials, but it is inherent to the initial accelerated sulfur vulcanization chemistry undergone by these materials.
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Mathew, George, P. Viswanathan Pillai, and A. P. Kuriakose. "Studies on a New Binary Accelerator System for the Sulfur Vulcanization of Styrene—Butadiene Rubber." Rubber Chemistry and Technology 65, no. 2 (May 1, 1992): 277–92. http://dx.doi.org/10.5254/1.3538611.
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Abstract The chemical reactions involved when a binary accelerator system is used in rubber vulcanization varies with the systems used. The exact mechanism of these reactions is not fully understood even now. Accelerators in which sulfur is combined as S—S, C—S—C, or S—N are generally inactive at low vulcanization temperatures because of the high thermal stability of their sulfur bonds. But sulfur-containing nucleophiles such as thiourea or its derivatives enable accelerators like TMTD or CBS to operate at lower vulcanization temperature, indicating a nucleophilic reaction mechanism in these vulcanization reactions. But, no conclusive evidence is given for such a postulate. In the present study, 1-phenyl-2,4-dithiobiuret and 1,5-diphenyl-2,4-dithiobiuret, which are more nucleophilic than thiourea but which vary in their nucleophilic reactivity, were tried as secondary accelerators in binary systems containing TMTD or CBS in sulfur vulcanization of SBR. Both the above dithiobiurets were found to reduce the optimum cure time considerably compared to the reference mixes. 1-phenyl-2,4-dithiobiuret, which is more nucleophilic than 1,5-diphenyl-2,4-dithiobiuret, is found to reduce the optimum cure time more, showing a nucleophilic reaction mechanism in the systems under review. In both cases, the optimum dosage of the secondary accelerator required has been established. The vulcanizates obtained with these new systems showed definite increase in tensile properties and good retention of these properties after aging. In the evaluation of other physical properties, these vulcanizates gave promising results. In order to correlate these physical properties to the type of chemical crosslinks formed, chemical characterization of the vulcanizates was also carried out. Also, to study the effect of these nucleophiles on the temperature of vulcanization, these mixes were cured and evaluated at two different temperatures, viz., 120°C and 150°C. To overcome the lower green strength and gum tensile strength in SBR, incorporation of fine reinforcing fillers and the use of special combinations of accelerators is required. In this context, the study was extended to evaluate the effect of fillers—carbon black, precipitated silica, and china clay—on the cure characteristics and vulcanizate properties.
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Liu, Qingqing, Kai Zhang, Xingshuo Zhang, and Zhaobo Wang. "Strengthening effect of Mullins effect of high- density polyethylene/ethylene–propylene–diene terpolymer thermoplastic vulcanizates under compression mode." Journal of Thermoplastic Composite Materials 31, no. 10 (October 30, 2017): 1310–22. http://dx.doi.org/10.1177/0892705717738288.
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Thermoplastic vulcanizates (TPVs) based on high-density polyethylene (HDPE)/ethylene–propylene–diene terpolymer (EPDM) were prepared via dynamic vulcanization. The mechanical properties and strengthening effect of Mullins effect under compression mode were investigated systematically. Experimental results indicated that the compression strength of TPVs was enhanced greatly compared with that of EPDM vulcanizate. Mullins effect could be observed obviously in the compression stress–strain curves of the TPVs while it was hardly to obverse in that of EPDM vulcanizate during the uniaxial loading–unloading cycles. The maximum compression stress and internal friction loss at specific strain were decreased after the first loading–unloading while only decreased slightly at the later loading–unloading cycles; however, the residual deformation increased with the increasing of the cycle times of compression. Mullins effect could be significantly enhanced with increasing compression strain and HDPE content in TPV.
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Chattaraj, P. P., R. Mukhopadhyay, and D. K. Tripathy. "Effect of trans-Polyoctenylene on Crosslink Structure of NR and SBR Using Solid State 13C NMR Spectroscopy and RPA 2000." Rubber Chemistry and Technology 70, no. 1 (March 1, 1997): 90–105. http://dx.doi.org/10.5254/1.3538421.
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Abstract The use of petroleum oil as a processing aid is well established in the rubber industry. However, it has certain demerits when used in a critical rubber compound. To overcome this and to get certain other advantages, new non-conventional processing aids (solid in nature) are preferred. trans-Polyoctenylene (TOR) is one of them which is crosslinkable with sulfur and accelerator. The effect of TOR on natural rubber (NR) and styrene—butadiene rubber (SBR) vulcanizates has shown that the retention (%) of network properties at high temperatures, after aerobic and anaerobic aging, is better with incorporation of TOR in conventional vulcanization (CV) curing systems. This has been attributed to the change of network to a more efficient-like system. The purpose of the present work is to establish the change of network structure/crosslinks and their kind and distribution in NR and SBR, with incorporation of TOR followed by a spectroscopic study of the vulcanizate. The study is extended to different crosslinking systems (CV, efficient vulcanization (EV), and semi-EV (SEV) with respect to NR and SBR) considering the effect of anaerobic aging on the vulcanizates. Crosslink distribution (in CV and EV) and network structural change after aging has been explained by a suitable mechanism. Elucidation of crosslink structure of SBR vulcanizates by NMR and estimation of chemical crosslink density by the Rubber Process Analyzer (RPA 2000) are key points of this study.
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Ushmarin, Nikolay F., Lyudmila Yu Tsareva, Ksenia A. Konnova, Maria V. Yakimova, and Nikolay I. Koltsov. "The influence of technological additives and peroxides on the properties of rubber mixtures based on ethylene propylene caoutchouc." Butlerov Communications 60, no. 10 (October 31, 2019): 81–87. http://dx.doi.org/10.37952/roi-jbc-01/19-60-10-81.
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The article investigates the influence of technological additives and peroxides on the properties of two rubber mixtures based on ethylene-propylene caoutchouc of marking SKEPT-40. The main properties were: rheometric (maximum and minimum torques; start, optimum and maximum vulcanization rates; maximum vulcanization rates), physical and mechanical (conditional tensile strength, elongation at break, hardness) and operational (changes in conditional strength at tensile, elongation at break and hardness after aging in air). The resistance of rubbers to the action of high temperatures by methods of differential thermal and thermogravimetric analysis was studied. As technological additives, MA-L22, Struktol WS180, Zincolet BB 222 and Struktol A89 were used. Vulcanizing agents were peroxides: Novoperox BP-40, Percodox BC-FF, Dicumyl Peroxide (DK), Chemanox PX1 and Dicumyl Peroxide DCP 99. The studies were carried out for two rubbers, one of which is intended for the manufacture of molded products, and the second rubber – for sealing profiles. It was shown that the technological additive Zincolet BB 222 increases the vulcanization rate of rubber mixture for molded products. All technological additives used have practically no effect on the conditional tensile strength and hardness vulcanizates of molded products, increasing their elongation at break. The smallest changes in the physical and mechanical properties are characterized by the vulcanizate, which contains the technological additive Zincolet BB 222. Technological additives practically do not affect the process of vulcanization of the rubber mixture and slightly affect the process of destruction of rubber during aging. Of the investigated technological additives Zincolet BB 222 is more conducive to improving the thermal properties of rubber. It has been established that Novoperox BP-40 and Chemanox PX1 peroxides increase the rate of vulcanization of the rubber mixture for sealing profiles. For vulcanizates of this rubber mixture, when Novoperox BP-40 and Chemanox PX1 is replaced with other peroxides, a decrease in the conditional tensile strength, hardness and an increase in the elongation at break are observed. With aging in air, changes in the physicomechanical properties of the vulcanizates of the rubber mixture variants containing Novoperox BP-40 and Chemanox PX1 are insignificant and close to each other.
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Udagawa, Y., and M. Ito. "Detection of the Molecular Orientation in Nonvulcanized and Vulcanized Natural Rubber Compounds by the Low-Temperature X-Ray Method." Rubber Chemistry and Technology 62, no. 2 (May 1, 1989): 179–94. http://dx.doi.org/10.5254/1.3536239.
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Abstract The low-temperature x-ray method can detect the orientation of NR molecules in both vulcanizate samples and nonvulcanizate samples of NR compounds. The presence of carbon black is important for causing the orientation. NR molecules orient in the direction of stretch-relaxation in the case of uniaxially fatigued vulcanizates or in the direction of shear in the case of nonvulcanizates prepared by various processing methods. The orientation of NR molecules in nonvulcanizates usually disappears when vulcanized, but a fairly large extent of molecular orientation remains, even after vulcanization, if there exist crosslinks in the oriented nonvulcanizate and the sample is prevented from shrinkage.
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Kruželák, Ján, Richard Sýkora, and Ivan Hudec. "Peroxide vulcanization of natural rubber. Part I: effect of temperature and peroxide concentration." Journal of Polymer Engineering 34, no. 7 (September 1, 2014): 617–24. http://dx.doi.org/10.1515/polyeng-2014-0034.
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Abstract Four different peroxides as curing agents were used to prepare vulcanizates based on natural rubber (NR). The effects of temperature and peroxide concentration on the vulcanization characteristics of rubber compounds, cross-link density (ν) and physical-mechanical properties of equivalent vulcanizates were investigated. The results revealed that the vulcanization temperature and also the relative amount of peroxide decomposition products are of significant importance in the properties of vulcanizates. Lower vulcanization temperature and lower concentration of peroxides were found to be better factors, showing a proper balance between the degree of cross-linking of the rubber and degradation of the macromolecular chains by side reactions in relation to the crystallization of NR, which imparts vulcanizates based on NR outstanding properties.
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Grima, M. M. Alvarez, A. G. Talma, R. N. Datta, and J. W. M. Noordermeer. "New Concept of Co-Agents for Scorch Delay and Property Improvement in Peroxide Vulcanization." Rubber Chemistry and Technology 79, no. 4 (September 1, 2006): 694–711. http://dx.doi.org/10.5254/1.3547961.
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Abstract Peroxide cure is an important and widely used cure system for rubber. Several properties obtained via peroxide vulcanization are superior and not achievable with sulfur vulcanization, e.g.: aging resistance, no reversion and low compression set. However, other properties such as tensile strength and dynamic properties, are inferior to those of sulfur vulcanizates. The use of co-agents in peroxide cure leads to a certain extent to improvement in mechanical properties such as tensile strength. Nevertheless the properties are still inferior with respect to mechanical/dynamical properties of sulfur-cured articles. If these properties can be improved, the range of applications of peroxide cure in the rubber industry can be significantly broadened. Scorch is a common problem in peroxide cure, especially for injection molding and extrusion applications. Several additives can help to improve scorch safety, however, they always result in a lower peroxide efficiency, thus inferior vulcanizate properties. In the present study a new concept of co-agents for peroxide vulcanization is introduced. This new concept consists of the use of a combination of a bismaleimide type co-agent, like N,N′-m-phenylenedimaleimide (BMI-MP), and a sulfur containing compound, like dipentamethylenethiuram tetrasulfide (DPTT). This combination provides scorch safety and at the same time improves the mechanical properties of the vulcanizates. Within the bismaleimide type co-agents N,N′-p-phenylenedimaleimide (BMI-PP) provides better mechanical properties than BMI-MP. The concentration of co-agent and sulfur containing compound have a big influence on the scorch time and on the mechanical properties. Optimal properties are reached with 4 phr of co-agent and 0.7 to 0.96 phr of sulfur containing compound.
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Rajan, Rejitha, Siby Varghese, and K. E. George. "ROLE OF COAGENTS IN PEROXIDE VULCANIZATION OF NATURAL RUBBER." Rubber Chemistry and Technology 86, no. 3 (September 1, 2013): 488–502. http://dx.doi.org/10.5254/rct.13.87984.
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ABSTRACT The drawbacks of peroxide vulcanization can largely be overcome by introducing suitable co-curing agents (coagents) in the formulation. The role of various coagents, such as zinc diacrylate (ZDA), trimethylolpropane trimethacrylate (TMPTMA), and triallyl cyanurate (TAC) in the peroxide vulcanization of natural rubber (NR) was studied by Fourier transform infrared spectroscopy. Cross-link density was measured by the equilibrium–swelling technique. Cross-linking mechanism of peroxide in NR was interpreted by comparing the spectra of cured and uncured vulcanizates. The predominance of hydrogen abstraction over the radical addition was established (at 160 °C). Coagent ZDA produces ionic as well as covalent cross-links in the vulcanizate. Ionic cross-links have the ability to slip along the hydrocarbon chains and thus resemble polysulfidic cross-links. Hence, ZDA can be chosen for applications where good mechanical properties are required. Coagent TMPTMA produces covalent cross-links between polymer chains and is suitable for high-modulus applications. TAC, although it bridges through covalent cross-links, is not a suitable coagent for highly unsaturated rubbers like NR.
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van Hoek, Hans, Jacques Noordermeer, Geert Heideman, Anke Blume, and Wilma Dierkes. "Best Practice for De-Vulcanization of Waste Passenger Car Tire Rubber Granulate Using 2-2′-dibenzamidodiphenyldisulfide as De-Vulcanization Agent in a Twin-Screw Extruder." Polymers 13, no. 7 (April 2, 2021): 1139. http://dx.doi.org/10.3390/polym13071139.
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De-vulcanization of rubber has been shown to be a viable process to reuse this valuable material. The purpose of the de-vulcanization is to release the crosslinked nature of the highly elastic tire rubber granulate. For present day passenger car tires containing the synthetic rubbers Styrene-Butadiene Rubber (SBR) and Butadiene Rubber (BR) and a high amount of silica as reinforcing filler, producing high quality devulcanizate is a major challenge. In previous research a thermo-chemical mechanical approach was developed, using a twin-screw extruder and diphenyldisulfide (DPDS) as de-vulcanization agent.The screw configuration was designed for low shear in order to protect the polymers from chain scission, or uncontrolled spontaneuous recombination which is the largest problem involved in de-vulcanization of passenger car tire rubber. Because of disadvantages of DPDS for commercial use, 2-2′-dibenzamidodiphenyldisulfide (DBD) was used in the present study. Due to its high melting point of 140 °C the twin-screw extruder process needed to be redesigned. Subsequent milling of the devulcanizate at 60 °C with a narrow gap-width between the mill rolls greatly improved the quality of the devulcanizate in terms of coherence and tensile properties after renewed vulcanization. As the composition of passenger car tire granulate is very complex, the usefulness of the Horikx-Verbruggen analysis as optimization parameter for the de-vulcanization process was limited. Instead, stress-strain properties of re-vulcanized de-vulcanizates were used. The capacity of the twin-screw extruder was limited by the required residence time, implying a low screw speed. A best tensile strength of 8 MPa at a strain at break of 160% of the unblended renewed vulcanizate was found under optimal conditions.
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Rajan, Rejitha, Siby Varghese, Meera Balachandran, and K. E. George. "RESPONSE SURFACE METHODOLOGY: A TOOL FOR ASSESSING THE ROLE OF COMPOUNDING INGREDIENTS IN PEROXIDE VULCANIZATION OF NATURAL RUBBER." Rubber Chemistry and Technology 89, no. 2 (June 1, 2016): 211–26. http://dx.doi.org/10.5254/rct.15.84864.
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ABSTRACT Response surface methodology was used for assessing the role of various compounding ingredients, including zinc oxide, antioxidant, coagent, oil, and filler, in peroxide vulcanization of natural rubber. A face-centered central composite design with four factors at three different levels was used to obtain the relationship between vulcanizate properties and the level of ingredients. The four factors selected were filler and oil ratio and the contents of zinc oxide, antioxidant, and coagent. The filler and oil ratio was kept constant throughout the experiment. The vulcanizates were evaluated for their mechanical properties: tensile strength, elongation, modulus (M100), tear strength, hardness, compression set (70 and 100 °C), and crosslink density. Regression equations were generated to model the properties of interest, and response surfaces and contour diagrams were plotted.
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Maciejewska, Magdalena, and Anna Sowińska-Baranowska. "The Synergistic Effect of Dibenzyldithiocarbamate Based Accelerator on the Vulcanization and Performance of the Silica-Filled Styrene–Butadiene Elastomer." Materials 15, no. 4 (February 15, 2022): 1450. http://dx.doi.org/10.3390/ma15041450.
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This work focused on studying the effect of dibenzyldithocarbamate vulcanization accelerator on the curing characteristics and performance of styrene–butadiene elastomer (SBR) filled with nanosized silica. A dibenzyldithocarbamate derivative was applied as an additional accelerator to enhance the efficiency and the rate of sulfur vulcanization in the presence of two other accelerators, i.e., N-cyclohexyl-2-benzothiazole sulfenamide (CBS) and/or 1,3-diphenylguanidine (DPG). Furthermore, the possibility of reducing the amount of zinc oxide (ZnO) and the elimination of CBS and DPG from elastomer compounds using dibenzyldithiocarbamate accelerator was tested. Dibenzyldithocarbamate derivative applied with other accelerators (especially CBS) effectively enhances the efficiency of SBR vulcanization by reducing the optimal vulcanization time and increasing the crosslink density of the vulcanizates despite the lower amount of ZnO. Moreover, vulcanizates with dibenzyldithocarbamate demonstrate higher tensile strength while having a smaller content of CBS or DPG compared to the reference SBR composites. Thus, the synergistic effect of dibenzydithiocarbamate derivative on the vulcanization and performance of SBR was confirmed. Furthermore, dibenzyldithocarbamate derivative enables the amount of ZnO to be reduced by 40% without harmful influence on the crosslink density and performance of the vulcanizates. Finally, it is possible to replace CBS with a dibenzyldithiocarbamate derivative without the crosslink density and tensile strength of the vulcanizates being adversely affected, while improving their resistance to thermo-oxidative aging.
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Munirah, N. R., N. Z. Noriman, M. Z. Salihin, Sung Ting Sam, Mohd Mustafa Al Bakri Abdullah, Kamarudin Hussin, H. Rosniza, and M. F. Omar. "The Effects of Trans-Polyoctylene Rubber (TOR) on the Cure Characteristics and Swelling Behaviour of Activated Carbon Filled Styrene Butadiene Rubber (SBR) Vulcanizates." Materials Science Forum 857 (May 2016): 164–68. http://dx.doi.org/10.4028/www.scientific.net/msf.857.164.
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Compatibilizer is one of the processing aids used for rubber compounding which helps the incorporation of filler in rubber. In this study, the effect of trans-polyoctylene rubber (TOR) as compatibilizer on the cure characteristics and swelling behaviour of activated carbon filled styrene butadiene rubber (SBR) vulcanizates were studied as a function of TOR loading. Both uncompatibilized and compatibilized SBR vulcanizates with different TOR loading (2, 4, 6 and 8 phr) were prepared using two-rolls mill at room temperature. It was observed that the cure time (tc90) of compatibilized SBR vulcanizates was shorter than that of the uncompatibilized SBR vulcanizate and decreased with increasing of TOR loading up to 6 phr. The minimum torque (ML) of the uncompatibilized SBR vulcanizate was lower compared to the compatibilized vulcanizates. In contrast, the uncompatibilized SBR vulcanizate has higher maximum torque (MH) compared to the compatibilized SBR vulcanizates. As the TOR contents increased, the ML increased but MH gradually decreased. It was also reported that the value of cure rate index (CRI) of the compatibilized SBR vulcanizates increased with the increment in addition of TOR. The result also showed that the compatibilized SBR vulcanizates had lower crosslink density than that of the uncompatibilized SBR vulcanizate and slightly decreased with increasing TOR loading.
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Mori, Kunio, Satoshi Kaneda, Kentaro Kanae, Hidetoshi Hirahara, Yoshiyuki Oishi, and Akira Iwabuchi. "Influence on Friction Force of Adhesion Force between Vulcanizates and Sliders." Rubber Chemistry and Technology 67, no. 5 (November 1, 1994): 797–805. http://dx.doi.org/10.5254/1.3538711.
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Abstract The effects of vulcanizate and slider surface free energy—as well as the adhesion force (P) between them—on friction the force (F) and the coefficient of friction (μ) has been investigated. SBR and NBR vulcanizates were prepared using three molds differing in surface free energy. The mold with a high surface free energy gave a vulcanizate surface possessing polar groups. The mold with low surface energy gave a vulcanizate surface with many nonpolar groups. The coefficient of friction increased with the surface free energy of SBR and NBR vulcanizates. With SBR vulcanizate (surface free energy, 31.3 mJ·m−2) and teflon slider (surface free energy, 28.1 mJ·m−2) combination having the least surface free energy, the coefficient of friction was constant at greater than a 0.2N load. With vulcanizates and an aluminum slider with high surface free energy, friction force could be detected even at zero load because of the adhesion force at the interface. Friction force increased linearly with adhesion force between vulcanizates and sliders when the physical properties of the vulcanizates and net work chain density were constant. The present results clearly demonstrate the contribution of adhesion force to the friction of vulcanizates.
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Verbruggen, M. A. L., L. van der Does, W. K. Dierkes, and J. W. M. Noordermeer. "EXPERIMENTAL VALIDATION OF THE CHARLESBY AND HORIKX MODELS APPLIED TO DE-VULCANIZATION OF SULFUR AND PEROXIDE VULCANIZATES OF NR AND EPDM." Rubber Chemistry and Technology 89, no. 4 (December 1, 2016): 671–88. http://dx.doi.org/10.5254/rct.16.83776.
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ABSTRACT The theoretical model developed by Charlesby to quantify the balance between cross-links creation of polymers and chain scission during radiation cross-linking and further modifications by Horikx to describe network breakdown from aging were merged to characterize the balance of both types of scission on the development of the sol content during de-vulcanization of rubber networks. There are, however, disturbing factors in these theoretical considerations vis-à-vis practical reality. Sulfur- and peroxide-cured NR and EPDM vulcanizates were de-vulcanized under conditions of selective cross-link and random main-chain scissions. Cross-link scission was obtained using thiol-amine reagents for selective cleavage of sulfur cross-links. Random main-chain scission was achieved by heating peroxide vulcanizates of NR with diphenyldisulfide, a method commonly employed for NR reclaiming. An important factor in the analyses of these experiments is the cross-linking index. Its value must be calculated using the sol fraction of the cross-linked network before de-vulcanization to obtain reliable results. The values for the cross-linking index calculated with sol-gel data before de-vulcanization appear to fit the experimentally determined modes of network scission during de-vulcanization very well. This study confirms that the treatment of de-vulcanization data with the merged Charlesby and Horikx models can be used satisfactorily to characterize the de-vulcanization of NR and EPDM vulcanizates.
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Thomas, Shaji P., Saliney Thomas, C. V. Marykutty, and E. J. Mathew. "Evaluation of Effect of Various Nanofillers on Technological Properties of NBR/NR Blend Vulcanized Using BIAT-CBS System." Journal of Polymers 2013 (September 17, 2013): 1–10. http://dx.doi.org/10.1155/2013/798232.
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Owing to processing ease and resistance to oils and chemicals, NBR is widely used in many industries. But since neat NBR has only poor tensile properties, it is better to use suitable blends of NR and NBR after incorporating appropriate nanoingredients before vulcanization. It is well established that nanoparticles can be easily dispersed in a more uniform pattern in polymer matrix, thereby enhancing the technological properties of the elastomer vulcanizate. Since there are no systematic comparative studies on technological properties of NBR/NR blend containing different nanoingredients, efforts have been made in this study to investigate cure and technological properties like tensile properties, tear resistance, compression set, hardness, abrasion loss and swelling value of NBR/NR (80/20) blend vulcanizates containing stearic acid-coated nano-zinc oxide (ZOS), nano-BIAT, nano-silicate-coated CaCO3, PEO-coated calcium silicate, and surface-modified carbon nanotubes (CNT). XRD and electron microscopy have been used for morphological analysis. The nano ingredients were effective in enhancing the technological properties of the vulcanizates. Among the nanofillers, modified CNT was found to impart superior properties to NBR/NR blend due to more intercalation.
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Joseph, Anu Mary, Benny George, Madhusoodanan K. N., and Rosamma Alex. "EFFECT OF DEVULCANIZATION ON CROSSLINK DENSITY AND CROSSLINK DISTRIBUTION OF CARBON BLACK FILLED NATURAL RUBBER VULCANIZATES." Rubber Chemistry and Technology 89, no. 4 (December 1, 2016): 653–70. http://dx.doi.org/10.5254/rct.16.84819.
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ABSTRACTCarbon black filled natural rubber (NR) vulcanizates were devulcanized at ambient temperature in a two roll mill. The effect of cure system, that is, conventional vulcanization (CV), semiefficient vulcanization (semi EV), and efficient vulcanization (EV) systems, used for vulcanization of the original sample, on the efficiency of devulcanization was studied. The efficiency of devulcanization expressed as percentage devulcanization of the samples calculated from residual crosslink density measurements was correlated with the sol fraction of the devulcanized samples based on Horikx analysis. Using chemical probe analysis, we determined (i) the crosslink distribution pattern of the original sample, (ii) the extent to which the different types of crosslinks—that is, polysulfidic, disulfidic, and monosulfidic crosslinks—have been debonded or broken during the shearing process in the two roll mill, and (iii) the pattern of bond formation during revulcanization. Mechanical shearing predominantly breaks the majority crosslink type (polysulfidic crosslinks in CV and semi EV cure systems and disulfidic crosslinks in EV samples). Irrespective of the significant reduction in total crosslink density in all three sets of samples, chain shortening reactions similar to the post-crosslinking chemical reactions at curing temperatures also occur during mechanical shear at ambient conditions, which increased the absolute value of monosulfidic links in CV and semi EV systems. However, in the devulcanized EV system, the absolute value of polysulfidic crosslinks increased, which might be due to the re-crosslinking of the cleaved bonds. All the devulcanized samples were revulcanized, and the mechanical and morphological properties were analyzed. The percentage retention of the vulcanizate properties after revulcanization of the devulcanized samples correlated very well with efficiency of devulcanization.
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Dziemidkiewicz, Anna, Magdalena Maciejewska, and Martyna Pingot. "Thermal analysis of halogenated rubber cured with a new cross-linking system." Journal of Thermal Analysis and Calorimetry 138, no. 6 (November 2, 2019): 4395–405. http://dx.doi.org/10.1007/s10973-019-08881-7.
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Abstract The aim of this work was to examine the influence of new curing agents proposed for brominated butyl rubber (BIIR) on the cross-linking process of rubber compounds and the thermal behavior of the vulcanizates. Rubber blends that were filled with carbon black and contained acetylacetonates of different transition metals in the presence of triethanolamine (TEOA) as new cross-linking agents were prepared. The performed studies showed that metal acetylacetonates (Me(acac)) are effective cross-linking agents for BIIR, which was confirmed by high values of the torque increment (∆M) and significant cross-linking degree of the vulcanizates (α(T)). The most active curing agent seems to be iron acetylacetonate (Fe(acac)). Its application results in a shorter optimal vulcanization time, lower onset vulcanization temperature and similar vulcanization enthalpy compared to the BIIR cured with a sulfur curing system. The BIIR vulcanizates cured with Me(acac) reveal good mechanical properties with tensile strengths in the range of 9–14 MPa and better damping properties comparing to the sulfur-cured rubber. The proposed curing agents do not significantly affect the thermal stability of the BIIR vulcanizates.
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Mori, Kunio, Yoshiyuki Oishi, Hidetoshi Hirahara, Naoaki Kumagai, and Kazuo Tanno. "Electropolymerization of Aniline on Conductive Vulcanizates and Charge-Discharge Properties." Rubber Chemistry and Technology 66, no. 5 (November 1, 1993): 806–16. http://dx.doi.org/10.5254/1.3538345.
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Abstract To obtain electrode materials with good charge-discharge properties, the electrochemical polymerization of aniline on conductive vulcanizates containing Ketjin black was investigated along with the charge-discharge properties of these materials. When EPDM vulcanizates containing Ketjin black greater than 20 phr were used as working electrodes, the polymerization of aniline occurred easily and conductive laminates of vulcanizate and polyaniline were obtained. This required an EPDM vulcanizate conductivity of more than 0.1 S/cm. The selection of elastomers and solvents for the electrochemical reaction is important. A combination of EPDM and water solvent was found to be suitable for the electrochemical polymerization of aniline. Polyaniline products on vulcanizate electrodes had lower film densities than polypyrrole products, and exhibited greater adhesion to the vulcanizates than to Pt electrodes. Li battery cells, using these polyaniline vulcanizate electrodes, possessed remarkably higher charge-discharge capacity and greater cycles life than the polyaniline Pt electrode. The vulcanizate electrode retained good charge-discharge properties even at a current density exceeding 1.0 mA/cm2.
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Chanpon, Kannika, Anoma Thitithammawong, Charoen Nakason, and Azizon Kaesaman. "Effect of Unmodified and Modified Epoxidized Soyabean Oils on Properties of Black-NBR Compounds and Black-NBR Vulcanizates." Advanced Materials Research 844 (November 2013): 49–52. http://dx.doi.org/10.4028/www.scientific.net/amr.844.49.
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In this study, feasibility of using epoxidized soyabean oil (ESO) and n-phenyl-p-phenylenediamine modified ESO (pA-m-ESO) as rubber processing oil in a formulation of carbon black filled acrylonitrile butadiene rubber (NBR) compound was investigated. It is seen that properties of the NBR compounds (i.e., total mixing energy, dump temperature, Mooney viscosity and curing characteristic) with using the DOP and the ESO were comparable, unlike the compound with using the pA-m-ESO. However, after vulcanization the NBR vulcanizate with using the DOP showed superior modulus, tensile strength and hardness than those of the others. This is due to interaction between the processing oil and the NBR phases as well as reinforcing effect of the carbon black on NBR molecules. However, no differences of dispersion and distribution of carbon black in the NBR vulcanizates with varying types of processing oil were observed.
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Sowińska, Anna, Magdalena Maciejewska, and Anna Grajewska. "Bis(trifluoromethylsulfonyl)imide Ionic Liquids Applied for Fine-Tuning the Cure Characteristics and Performance of Natural Rubber Composites." International Journal of Molecular Sciences 22, no. 7 (April 1, 2021): 3678. http://dx.doi.org/10.3390/ijms22073678.
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The goal of this work was to apply ionic liquids (ILs) with bis(trifluoromethylsulfonyl)imide anion (TFSI) for fine-tuning the cure characteristics and physico-chemical properties of elastomer composites based on a biodegradable natural rubber (NR) matrix. ILs with TFSI anion and different cations, such as alkylpyrrolidinium, alkylammonium, and alkylsulfonium cations, were applied to increase the efficiency of sulfur vulcanization and to improve the performance of NR composites. Thus, the influence of ILs on the vulcanization of NR compounds, as well as crosslink density and physical properties of NR vulcanizates, including tensile properties, thermal stability, and resistance to thermo-oxidative aging was explored. The activity of ILs seems to be strongly dependent on their cation. Pyrrolidinium and ammonium ILs effectively supported the vulcanization, reducing the optimal vulcanization time and temperature of NR compounds and increasing the crosslink density of the vulcanizates. Consequently, vulcanizates with these ILs exhibited higher tensile strength than the benchmark without IL. On the other hand, sulfonium ILs reduced the torque increment owing to the lower crosslinking degree of elastomer but significantly improved the resistance of NR composites to thermo-oxidation. Thus, TFSI ILs can be used to align the curing behavior and performance of NR composites for particular applications.
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Munirah, N. R., N. Z. Noriman, M. Z. Salihin, H. Kamarudin, M. H. Fatin, S. T. Sam, and A. M. Mustafa Al Bakri. "The Effects on the Cure Characteristics and Physical Properties of Bamboo Activated Carbon Filled Styrene Butadiene Rubber (SBR) Compounds." Applied Mechanics and Materials 815 (November 2015): 24–28. http://dx.doi.org/10.4028/www.scientific.net/amm.815.24.
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The role of activated carbon (AC) in rubber compounds was investigated to better understand the reinforcing mechanism. The activated carbon filled styrene butadiene rubber vulcanizates (SBR-AC) using bamboo activated carbon as filler were prepared by using two-roll mill and cured at 160 °C. AC filler loading from 10 to 50 phr (part per hundred rubber) were used in this study. Study into the influences of filler loading on the cure characteristics, swelling behaviour and physical properties (hardness and resilience) of SBR-AC vulcanizates were carried out. It was observed that SBR-AC vulcanizates has better cure characteristics compared to the styrene butadiene rubber gum vulcanizate (SBR-GV) which is a non-filled vulcanizate. The results showed that the scorch time (ts2) decreased with increasing filler loading. The cure time (tc90) slightly decreased up to 20 phr before a rise as the filler loading increased. The minimum torque (ML) of SBR vulcanizate increased and the maximum torque (MH) decreased up to 20 phr but then increased with increasing filler loading. The cure rate index (CRI) of SBR-GV vulcanizate was higher than that of all SBR-AC vulcanizates. Up to 20 phr of filler loading, the CRI increased before a decline occurred as the filler loading increased. As expected, the hardness value of SBR-AC vulcanizates was higher compared to SBR-GV vulcanizate which has lower resilience. The hardness and crosslink density showed an increasing trend meanwhile the resilience was adversely affected by the increase in filler loading. Bamboo activated carbon showed some potential enhancement on the reinforcing and physical properties of the vulcanizates.
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Maciejewska, Magdalena, and Monika Siwek. "The Influence of Curing Systems on the Cure Characteristics and Physical Properties of Styrene–Butadiene Elastomer." Materials 13, no. 23 (November 25, 2020): 5329. http://dx.doi.org/10.3390/ma13235329.
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The goal of this work is to study the influence of different curing systems on the cure characteristics and performance of styrene–butadiene elastomer (SBR) filled with carbon black or nanosized silica. A multifunctional additive for rubber compounds, namely Activ8, was applied as an additional activator and accelerator to increase the efficiency of sulfur vulcanization and to reduce the content of zinc oxide elastomers cured in the presence of 2-mercaptobenzothizole or 1,3-diphenylguanidine as a primary accelerator. The influence of the curing system composition on the crosslink density and physical properties of SBR vulcanizates, such as mechanical properties, thermal stability, and resistance to thermo-oxidative aging, is also reported. Activ8 effectively supports the vulcanization of SBR compounds, especially filled with nanosized silica. It reduces the optimal vulcanization time of SBR compounds and increases the crosslink density of the vulcanizates. Moreover, vulcanizates with Activ8 exhibit higher tensile strength and better damping properties than elastomer with zinc oxide. Activ8 allows the amount of ZnO to be reduced by 40% without detrimental effects on the crosslink density and mechanical performance compared to the vulcanizates conventionally crosslinked with ZnO. This is an important ecological goal since ZnO is classified as being toxic to aquatic species.
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Nasruddin, Nasruddin, and Tri Susanto. "Study of the Mechanical Properties of Natural Rubber Composites with Synthetic Rubber Using Used Cooking Oil as a Softener." Indonesian Journal of Chemistry 20, no. 5 (July 18, 2020): 967. http://dx.doi.org/10.22146/ijc.42343.
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This research aims to study the mechanical properties of natural rubber composites with nitrile butadiene rubber and ethylene propylene diene monomer rubber. Composite fillers consisted of kaolin, and softener using used cooking oil. The study was carried out by the method of mastication, vulcanization, and maturation of the compound into rubber vulcanizates. The vulcanization and mastication process is carried out in the open mill. The maturation of the compound into rubber vulcanizates from the results of mastication and vulcanization was carried out using semi-automatic heat press and press at a temperature of 130 °C ± 2 °C for 17 min. Based on data from testing the mechanical properties of five samples from five formulas, the mechanical properties of composite rubber are affected by the ratio of natural rubber, synthetic rubber, kaolin, and used cooking oil as a softener. The difference in the results of vulcanizates rubber testing of natural rubber composites with synthetic rubber is not only influenced by the ratio of the composite, but also by the degree of cross-linking between the material molecules.
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Maciejewska, Magdalena, and Anna Sowińska-Baranowska. "Bromide and Chloride Ionic Liquids Applied to Enhance the Vulcanization and Performance of Natural Rubber Biocomposites Filled with Nanosized Silica." Nanomaterials 12, no. 7 (April 4, 2022): 1209. http://dx.doi.org/10.3390/nano12071209.
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In this study, the possibility of using ionic liquids (ILs) as auxiliary substances improving the vulcanization and physicochemical properties of natural rubber (NR) biocomposites filled with nanosized silica was investigated. Hence, the influence of ILs with bromide and chloride anions and various cations, i.e., alkylimidazolium, alkylpyrrolidinium and alkylpiperidinium cation, on the curing characteristics and crosslink density of NR compounds was determined. Furthermore, the effect of nanosized silica and ILs on the functional properties of the obtained vulcanizates, including mechanical properties under static and dynamic conditions, hardness, thermal stability and resistance to thermo-oxidative aging, were explored. Applying nanosized silica improved the processing safety of NR compounds but significantly increased the optimal vulcanization time compared to the unfilled rubber. ILs significantly improved the cure characteristics of NR compounds by increasing the rate of vulcanization and the crosslink density of NR biocomposites. Consequently, the tensile strength and hardness of the vulcanizates significantly increased compared to that without ILs. Moreover, the use of nanosized silica and ILs had a favorable impact on the thermal stability of the vulcanizates and their resistance to prolonged thermo-oxidation.
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Bieliński, Dariusz M., Katarzyna Klajn, Tomasz Gozdek, Rafał Kruszyński, and Marcin Świątkowski. "Influence of n-ZnO Morphology on Sulfur Crosslinking and Properties of Styrene-Butadiene Rubber Vulcanizates." Polymers 13, no. 7 (March 26, 2021): 1040. http://dx.doi.org/10.3390/polym13071040.
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This paper examines the influence of the morphology of zinc oxide nanoparticles (n-ZnO) on the activation energy, vulcanization parameters, crosslink density, crosslink structure, and mechanical properties in the extension of the sulfur vulcanizates of styrene-butadiene rubber (SBR). Scanning electron microscopy was used to determine the particle size distribution and morphology, whereas the specific surface area (SSA) and squalene wettability of the n-ZnO nanoparticles were adequately evaluated using the Brunauer–Emmet–Teller (BET) equation and tensiometry. The n-ZnO were then added to the SBR in conventional (CV) or efficient (EV) vulcanization systems. The vulcametric curves were plotted, from which the cure rate index (CRI) rate of the vulcanization and the activation energy were calculated. The influence on the mechanical properties of the SBR vulcanizates was stronger in the case of the EV curing system than when the CV curing system was used. Of the vulcanizates produced in the EV curing system, the best performance was detected for n-ZnO particles with a hybrid morphology (flat-ended rod-like particles on a “cauliflower” base) and high SSA. Vulcanizates produced using the CV curing system showed slightly better mechanical properties after the addition of nanoparticles with a “cauliflower” morphology than when the rod-like type were used, irrespective of their SSA. In general, nanoparticles with a rod-like structure reduced the activation energy and increased the speed of vulcanization, whereas the cauliflower type slowed the rate of the process and the vulcanizates required a higher activation energy, especially when using the EV system. The crosslink structures were also more clearly modified, as manifested by a reduction in the polysulfidic crosslink content, especially when n-ZnO activators with a rod-like morphology were applied.
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Anjum, Hirra, Syed Waqas Ahmad, Rabia Sharif, and Muhammad Tausif. "Effect of filler type and composition on the mechanical, thermal, and dynamic mechanical properties of PS/SBR vulcanizate." Journal of Polymer Engineering 36, no. 6 (August 1, 2016): 607–14. http://dx.doi.org/10.1515/polyeng-2015-0066.
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Abstract Dynamic vulcanization is an eminent industrial process to enhance the physical, thermal, and rheological properties of polymer composites. The present experimental study comprised the formation of polystyrene (PS) and styrene butadiene rubber (SBR) composites using three different types of fillers, namely, kaolin, talc, and rice husk powder (RHP), whereas dicumylperoxide was added as a cross-linking agent. Further, the filler loading was varied from 0 to 20 parts per hundred of resin (phr) for all types (i.e. RHP). The mechanical (i.e. tensile strength, elongation at break, and impact strength), thermal (i.e. melting point and softening point index), and dynamic mechanical properties of each composite were measured and compared with each other. The results indicate that kaolin-based vulcanizate showed better mechanical, thermal, and dynamic mechanical properties compared to that of talc and RHP vulcanizate. Furthermore, it can be observed that the mechanical, thermal, and dynamic mechanical properties of PS/SBR vulcanizates are the function of filler loadings for all three types of fillers (i.e. kaolin, talc, and RHP). In addition, high-temperature storage properties (i.e. loss modulus and storage modulus) were also investigated for better design and material optimization. The study may be helpful to the tribological applications in material selection and design.
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Pajtášová, Mariana, Zuzana Mičicová, Darina Ondrušová, Slavomíra Božeková, Róbert Janík, Beáta Pecušová, and Lukáš Raník. "Use of waste materials in rubber matrix." MATEC Web of Conferences 157 (2018): 07009. http://dx.doi.org/10.1051/matecconf/201815707009.
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The presented paper deals with the use of waste materials as ecological fillers into rubber matrix. Waste materials were used as partial replacement of the commercial filler – carbon black, designated as N339. These prepared rubber compounds were characterized on the basis of the rheology and vulcanization characteristics – minimum torque (ML), maximum torque (MH), optimum time of vulcanization (t(c90)), processing safety of compound (ts), rate coefficient of vulcanization (Rv). In the case of the prepared vulcanizates, physical-mechanical properties (tensile strength, tensibility and hardness) and dynamic-mechanical properties (storage modulus, loss modulus, loss angle tan δ) were investigated. Using the dependency of loss angle on temperature, the selected properties for tyre tread vulcanizates were evaluated, including traction on snow and ice, traction on the wet surface and rolling resistance.
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Munirah, N. R., N. Z. Noriman, M. Z. Salihin, H. Kamaruddin, M. H. Fatin, S. T. Sam, A. M. Mustafa Al Bakri, and H. Rosniza. "The Effects on Cure Characteristics, Physico-Mechanical Properties and Morphology of Bamboo Activated Carbon Filled Styrene Butadiene Rubber (SBR) Vulcanizates." Key Engineering Materials 673 (January 2016): 131–40. http://dx.doi.org/10.4028/www.scientific.net/kem.673.131.
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The role of activated carbon (AC) in rubber compounds was investigated to better understand the reinforcing mechanism. The activated carbon filled styrene butadiene rubber vulcanizates (SBR-AC) using bamboo activated carbon as filler were prepared by using two-roll mill and cured at 160 °C. AC filler loading from 10 to 50 phr (part per hundred rubber) were used in this study. Study into the influences of filler loading on the cure characteristics, swelling behavior, physical properties (hardness and resilience), mechanical properties (tensile properties) and morphology of SBR-AC vulcanizates were carried out. It was observed that SBR-AC vulcanizates has better cure characteristics compared to the styrene butadiene rubber gum vulcanizate (SBR-GV) which is a non-filled vulcanizate. The results showed that the scorch time (ts2) decreased with increasing filler loading. The cure time (tc90) slightly decreased up to 20 phr before a rise as the filler loading increased. The minimum torque (ML) of SBR vulcanizate increased and the maximum torque (MH) decreased up to 20 phr but then increased with increasing filler loading. The cure rate index (CRI) of SBR-GV vulcanizate was higher than that of all SBR-AC vulcanizates. Up to 20 phr of filler loading, the CRI increased before a decline occurred as the filler loading increased. As expected, the hardness value of SBR-AC vulcanizates was higher compared to SBR-GV vulcanizate which has lower resilience. The hardness and crosslink density showed an increasing trend meanwhile the resilience was adversely affected by the increase in filler loading. The tensile properties of SBR-AC vulcanizates also showed improvement in which the tensile strength and modulus at 100% elongation (M100) increased with increasing filler content. It has been proved in morphology study of the tensile fracture surfaces. Bamboo activated carbon showed some potential enhancement on the reinforcing and physical properties as well as mechanical properties of the vulcanizates.
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Ushmarin, Nikolay F., Evgeny N. Egorov, and Nikolay I. Kol'tsov. "The study of the possibility of using domestic burnt magnesia in oil and petrol resistant rubber." Butlerov Communications 59, no. 7 (July 31, 2019): 63–68. http://dx.doi.org/10.37952/roi-jbc-01/19-59-7-63.
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The article examines the oil-and-petrol resistant rubber mixture of type 7NO-68-1SK based on the combination of BNKS-18AMN grade butadiene-caoutchouc with polychloroprene caoutchouc of brand neoprene W. The effect of replacing imported burnt magnesia brand Remag AC on domestic burnt magnesia technical grade B on the properties of the rubber compound and vulcanizate was studied. The rubber mixture was prepared on a laboratory roll mill LB 320 160/160, and then its standard samples were vulcanized at 150 °C for 30 minutes in a two-story electrically heated press of the VP 400-2E brand. To establish the plasto-elastic properties of rubber mixture on the Mooney viscometer, MV 3000 was determined: the start time of the vulcanization, the time to reach the vulcanization mode, the initial maximum viscosity. To assess the kinetics of vulcanization of the rubber mixture on the rheometer MDR 3000 was determined: the start time of vulcanization, the time to reach the optimum vulcanization, the maximum torque. To assess the physicomechanical properties of rubber, the following were determined: conditional tensile strength; elongation at break; hardness; tear resistance and relative residual deformation under compression in accordance with the standards in force in the rubber industry. To assess the performance properties of rubber, changes in its mass were determined after aging in a mixture of isooctane + toluene, as well as standard liquid SJR–1. It has been shown that the introduction of burnt magnesia technical grade B into the rubber mixture does not lead to technological complications, magnesia is well distributed in the rubber matrix, and the magnesia agglomerates were not found on the rubber mixture sections. Replacement magnesium oxide m. Remag AC on burnt magnesia technical grade B has an impact on the plasto-elastic and rheometric properties of the rubber mixture. However of physicomechanical and operational properties vulcanizates of rubber mixture containing magnesium oxide m. Remag AC and burnt magnesiatechnical grade B, have almost the same values.
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Maciejewska, Magdalena, Anna Sowińska, and Agata Grocholewicz. "Zinc Complexes with 1,3-Diketones as Activators for Sulfur Vulcanization of Styrene-Butadiene Elastomer Filled with Carbon Black." Materials 14, no. 14 (July 7, 2021): 3804. http://dx.doi.org/10.3390/ma14143804.
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Zinc oxide nanoparticles (N-ZnO) and zinc complexes with 1,3-diketones of different structures were applied instead of microsized zinc oxide (M-ZnO) to activate the sulfur vulcanization of styrene-butadiene rubber (SBR). The influence of vulcanization activators on the cure characteristics of rubber compounds, as well as crosslink density and functional properties of SBR vulcanizates, such as tensile properties, hardness, damping behavior, thermal stability and resistance to thermo-oxidative aging was explored. Applying N-ZnO allowed to reduce the content of zinc by 40% compared to M-ZnO without detrimental influence on the cure characteristic and performance of SBR composites. The activity of zinc complexes in vulcanization seems to strongly depend on their structure, i.e., availability of zinc to react with curatives. The lower the steric hindrance of the substituents and thus the better the availability of zinc ions, the greater was the activity of the zinc complex and consequently the higher the crosslink density of the vulcanizates. Zinc complexes had no detrimental effect on the time and temperature of SBR vulcanization. Despite lower crosslink density, most vulcanizates with zinc complexes demonstrated similar or improved functional properties in comparison with SBR containing M-ZnO. Most importantly, zinc complexes allowed the content of zinc in SBR compounds to be reduced by approximately 90% compared to M-ZnO.
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Mandal, Swapan Kumar, Md Najib Alam, Kumarjyoti Roy, and Subhas Chandra Debnath. "RECLAIMING OF GROUND RUBBER TIRE BY SAFE MULTIFUNCTIONAL RUBBER ADDITIVES: II VIRGIN NATURAL RUBBER/RECLAIMED GROUND RUBBER TIRE VULCANIZATES." Rubber Chemistry and Technology 87, no. 1 (March 1, 2014): 152–67. http://dx.doi.org/10.5254/rct.13.87899.
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ABSTRACT Mechanochemically reclaimed ground rubber tire (GRT) was revulcanized in combination with virgin natural rubber (NR). The NR/GRT vulcanizates with GRT content 20–50 wt% were prepared and studied. Reclaiming of GRT was successfully carried out by tetra benzyl thiuram disulfide (TBzTD) in the presence of spindle oil at around ambient temperature. The cure characteristics and mechanical properties of the virgin NR/reclaimed GRT blend were studied. Increasing the reclaimed rubber (RR) content in the blend decreases the optimum cure time without altering the scorch time. The effect of carbon black was studied in NR/RR (80/20) blend vulcanizate for the ultimate use of NR/RR blend vulcanizate. Aging characteristics of different NR/RR blends were evaluated. The swelling behavior, thermo-gravimetric analysis, and dynamic mechanical properties of NR/RR blend vulcanizates were examined. The equilibrium swelling of the NR vulcanizates was reduced with increasing reclaimed rubber content. Thermal stability of the blend vulcanizates was increased with increase in reclaimed rubber content. The elastic and storage modulus of the NR/RR vulcanizates improved with increasing reclaimed rubber content. Scanning electron microscopy studies further indicate the coherency and homogeneity in the NR/RR vulcanizate.
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Krejsa, M. R., and J. L. Koenig. "Solid State Carbon-13 NMR Studies of Elastomers. XL N-t-Butyl Benzothiazole Sulfenimide Accelerated Sulfur Vulcanization of cis-Polyisoprene at 75 MHz." Rubber Chemistry and Technology 66, no. 1 (March 1, 1993): 73–82. http://dx.doi.org/10.5254/1.3538300.
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Abstract The network structure of TBSI-accelerated vulcanization of cis-polyisoprene was studied using C-13 solid-state NMR. The initial crosslink products consisted of A1c (cis) and A2c (cis) polysulfides. As the percent cure is increased, the A1c and A2c structures reduce in rank to monosulfides, and polysulfidic B1c (cis) and B1t (trans) structures are formed. During the maturation period C1c (cis) polysulfidic structures are also formed. The percent of sulfurization was shown to vary directly with sulfur concentration, while the efficiency of sulfurization (crosslink/cyclic-structure ratio) was shown to vary with accelerator content. TBSI-accelerated vulcanization was found to be more inefficient (lower crosslink/cyclic-structure ratio) than TBBS-accelerated vulcanization during the initial cure region. However, this results in shorter sulfur chains, which decreases the reactivity of TBSI vulcanizates as compared to TBBS vulcanizates during the reversion regime.
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Volfson, Svetoslav Isaakovich, N. A. Okhotina, and Alina Ildusovna Nigmatullina. "Thermoplastic Vulcanizates Filled with а Layered Silicate." Key Engineering Materials 816 (August 2019): 119–23. http://dx.doi.org/10.4028/www.scientific.net/kem.816.119.
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Oil-resistant and thermoformed thermoplastic vulcanizates based on butadiene-nitrile rubber and polypropylene were obtained, containing a layered silicate montmorillonite as a filler. The structural characteristics of composites based on thermoplastic vulcanizates were studied using the methods of fractal analysis. It has been established that the value of the static flexibility of the polymer chain of a thermoplastic vulcanizate containing montmorillonite exceeds the static flexibility of the polymer chain of an unfilled thermoplastic vulcanizate. It is shown that the introduction of montmorillonite in the amount of 1-3 pbw in thermoplastic vulcanizates leads to improved performance characteristics of the obtained composites.
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Wang, Jingyi, Yu Meng, Tao Lu, Jiabin Zhang, Huajin Wang, Jialiang Sheng, Chunhui Huang, and Zusheng Hang. "Influence of melamine formaldehyde microsphere on the vulcanization kinetics and mechanical properties of nitrile butadiene rubber." Journal of Elastomers & Plastics 51, no. 2 (April 11, 2018): 143–56. http://dx.doi.org/10.1177/0095244318769959.
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The melamine formaldehyde (MF) microsphere/nitrile butadiene rubber (NBR) vulcanizates were prepared by adding MF into NBR through mechanical mixing, followed by a vulcanization process. The influences of MF on the vulcanization characteristics, vulcanization kinetics, and mechanical properties were investigated. The results showed that MF interacted with NBR through hydrogen bonds. In addition, parameter b calculated by the ratio of modulus and strains also demonstrated the strong interaction between MF and NBR. Adding MF into NBR would reduce the curing time of NBR compounds, and increase the curing rate, as well as the cross-linked density. The vulcanization kinetics of MF/NBR compounds could be simulated accurately by Ghoreishy’s model. The mechanical properties of MF/NBR increased with the incorporation of MF. The modulus at 100%, modulus at 300%, and tensile strength of NBR vulcanizates with 20 parts per hundred rubber MF had 155, 90, and 110% increment, respectively, compared with those of neat NBR. The MF also enhanced the tear strength of NBR by 80% with a rough tear-fractured surface of NBR recorded by scanning electron microscope.
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Egorov, Evgeniy N., Nikolay I. Kol'tsov, Nikolay F. Ushmarin, and Sergey I. Sandalov. "RESEARCH OF OPERATIONAL AND DYNAMIC PROPERTIES OF RUBBER FOR PRODUCTS WORKING IN SEA WATER." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 63, no. 11 (October 27, 2020): 96–102. http://dx.doi.org/10.6060/ivkkt.20206311.6307.
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The article studies the effect of trans-polynorbornene, general and special-purpose rubbers and fillers on the vulcanization characteristics of a rubber mixture, physical, mechanical, operational and dynamic properties of vulcanizates based on butadiene methylstyrene caoutchouc. The investigated model rubber mixture included SKMS-30ARK rubber, sulfur, 2,2'-dibenzthiazole disulfide, guanide F, zinc white, stearic acid, phenyl-2-naphthalamine, N-isopropyl-N'-phenyl-para-phenylenediamine, carbon blacks of grades P 514 and N 220, shungite powder and other ingredients. The rubber mixture was produced on laboratory rolls LB 320 160/160. The first (basic) version of the rubber mixture contained industrial oil I-12A as a softener. The second version of the mixture contained a modifying additive based on trans-polynorbornene and industrial oil I-12A. The third, fourth and fifth versions were prepared on the basis of a combination of rubbers SKMS-30ARK, SKN-4065 and BK-1675, including a modifying additive, as well as polyisobutylene P-118 and sevilen 11808-340. The vulcanization characteristics of the rubber mixture were studied on an MDR 3000 Basic rheometer at 150 °C for 30 min. To determine the physical and mechanical properties of rubber, standard samples of all variants of the rubber mixture were vulcanized at a temperature of 143 °C for 30 min in a vulcanization press of the P-V-100-3RT-2-PCD type. Studies of the physical, mechanical, operational and dynamic properties of rubber were carried out in accordance with the existing standards for the rubber industry. It is shown that vulcanizates containing a modifying additive have lower values of conventional tensile strength, hardness and tear resistance compared to vulcanizate of the base version of the rubber mixture and are characterized by increased dynamic and performance properties. Rubber containing a combination of butadiene-nitrile, butadiene-methylstyrene caoutchoucs and butyl caoutchouc, 10.0 mass parts sevilen 11808-340, 20.0 mass parts of trans-polynorbornene composed of in the modifying additive and 55.0 mass parts of carbon black P 324, possesses improved physical, mechanical and dynamic properties, as well as high resistance in sea water.
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Gelling, I. R., and N. J. Morrison. "Sulfur Vulcanization and Oxidative Aging of Epoxidized Natural Rubber." Rubber Chemistry and Technology 58, no. 2 (May 1, 1985): 243–57. http://dx.doi.org/10.5254/1.3536063.
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Abstract 1. Vulcanization by sulfur alone is faster and more efficient for ENR than for NR because isolated double bonds react more rapidly than contiguous double bonds. This vulcanization may be accelerated by sodium carbonate, which also protects the cured rubber against the subsequent effect of oxidative aging, and the scorch time may be increased by the addition of CTP. 2. The CBS-accelerated sulfur vulcanization of ENR is essentially similar to that of NR, although ENR reacts with MBT formed during the process. 3. The poor aging of sulfur vulcanizates of ENR is due to acid-catalyzed ring-opening reactions of the epoxide groups with the formation of ether crosslinks. The acids are produced by the thermal decomposition of oxidized sulfides. 4. The addition of a suitable base confers excellent resistance to oxidative aging upon conventional, semi-efficient, and efficient vulcanizates of ENR.
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Khachaturov, A. A., E. E. Potapov, S. V. Reznichenko, and A. N. Kovaleva. "Influence of iron ore concentrate (magnetite) on the kinetics of butadiene–styrene rubber-based blend curing in the presence of different accelerators." Fine Chemical Technologies 15, no. 5 (November 14, 2020): 46–53. http://dx.doi.org/10.32362/2410-6593-2020-15-5-46-53.
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Objectives. To investigate the possibility of using a cheaper ingredient, such as magnetite, in the synthesis of rubber compounds based on butadiene–styrene rubber by examining its effect on the process of sulfuric vulcanization of butadiene–styrene rubber in the presence of various accelerators.Methods. The influence of magnetite on the vulcanization kinetics was studied using an Alpha Technologies PRPA 2000 rotorless rheometer. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were performed using a Mettler Toledo TGA/DSC 2 device to evaluate the effect of magnetite on the butadiene–styrene rubber-based vulcanizates’ oxidation.Results. Magnetite was found to affect the kinetics of SBR-1500 butadiene–styrene rubber sulfuric vulcanization in the presence of thiazole-type accelerators (2-MBT, 2-MBS); in contrast, magnetite was inactive in the case of diphenylguanidine, sulfenamide T, and tetramethylthiuram disulfide. The obtained TGA/DSC data showed that magnetite has no significant effect on the butadiene–styrene rubber-based vulcanizates’ oxidation and thermal destruction.Conclusions. The obtained data confirmed magnetite’s capability to act as a butadiene–styrene rubber sulfuric vulcanization activator in the presence of various accelerators. The most significant effect was observed in the presence of thiazole-type accelerators.
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Ushmarin, Nikolay F., Evgeny N. Egorov, and Nikolay I. Kol'tsov. "INFLUENCE OF MICROSPHERES ON PROPERTIES OF AGGRESSIVE RESISTANT RUBBERS." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 64, no. 2 (January 29, 2021): 49–55. http://dx.doi.org/10.6060/ivkkt.20216402.6165.
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The aim of the work is to study the effect of hollow corundum, glass and pomegranate ceramic microspheres on the rheometric characteristics of aggressive resistant rubber mixtures and the physicomechanical parameters of their vulcanizates to determine of the content of fillers of this type, which provides an improvement in the priority properties of products and, as a result, an increase in their durability. The objects of research were two rubber mixtures intended for compression molding and injection molding. The compression molding mixture is based on a combination of nitrile butadiene, isoprene and butadiene-α-methyl styrene caoutchoucs with colloidal silicic acids as the main fillers. And the injection molding mixture is based on a combination of synthetic isoprene and butadiene rubbers filled with chalk, P234 carbon black and carbon 100. We used hollow corundum (HMC-L), glass (MS-V), and pomegranate ceramic (MVMD-170) microspheres. The rheometric properties of the rubber compounds were evaluated by the values of the minimum and maximum torques, the duration of the induction period, the time to reach the technological optimum, and the maximum vulcanization rate. When testing vulcanizates, conditional tensile strength, elongation at break, tear resistance, hardness, abrasion and rebound elasticity were determined. Priority indicators were also determined that correlated to the greatest extent with the durability of the products during operation - relative changes in conditional tensile strength and elongation at break, hardness after heat aging in air and standard liquid SZhR-1, change in mass of samples after swelling in industrial oil I-20A and Nefras S-80/120. For a mixture for compression molding, the effect of the type of microspheres introduced at a dosage of 5 parts by mass per 100 parts by mass caoutchoucs, on the properties of unvulcanized mixtures and vulcanizates was studied. It was found that the rubber mixture with glass microspheres is somewhat below in vulcanization activity, and its vulcanizate in terms of abrasion resistance, heat aging, especially in air, is inferior to two mixtures and rubbers with corundum and pomegranate microspheres. In the second mixture, we tested corundum microspheres with a dosage of 3.0 to 7.0 parts by mass per 100 parts by mass of caoutchoucs while reducing by the appropriate amount of carbon black. It was found that with an increase in the dosage of microspheres, a decrease in the vulcanization activity of the mixture, minimum and maximum torques, and also their difference is observed, which indicates a slight decrease in the degree of crosslinking of rubbers. The consequence is an increase in relative lengtheningof the vulcanizates. To the least extent, this effect manifests itself with the introduction of corundum microspheres in a dosage of 3 parts by mass. Thus, the advantage of rubbers with microspheres is reduced abrasion, higher tear resistance while maintaining resistance to the action of physically and chemically aggressive environments at the level of rubbers that do not contain microspheres.
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Gibala, David, and Gary R. Hamed. "Cure and Mechanical Behavior of Rubber Compounds Containing Ground Vulcanizates. Part I—Cure Behavior." Rubber Chemistry and Technology 67, no. 4 (September 1, 1994): 636–48. http://dx.doi.org/10.5254/1.3538699.
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Abstract SBR compounds containing ground vulcanizates of known composition and cure state were prepared and the cure behavior studied. Decreases in scorch times and maximum rheometer torques were observed when ground vulcanizates were added to the SBR compounds. Two primary phenomena are proposed to explain these findings: (1) migration of sulfur from the matrix rubber to the ground vulcanizate (causing torque reduction) and (2) migration of accelerator fragments from the ground vulcanizate to the matrix (causing decreased scorch time). The first proposal is based on direct measurement of sulfur concentrations in both ground particles and the matrix. The second is based on the detection, by high performance liquid chromatography, of mercaptobenzothiazole in the extract from ground vulcanizates. The second also is inferred from the fact that ground vulcanizate particles cured with peroxide do not alter scorch time. Moreover, a compound containing sulfur and ground (accelerated-sulfur vulcanized) rubber, but no added accelerator, nonetheless exhibits acceleration of cure.
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Antunes, C. F., A. V. Machado, and M. van Duin. "Degradation of the Rubber Network during Dynamic Vulcanization of EPDM/PP Blends Using Phenolic Resol." Rubber Chemistry and Technology 82, no. 5 (November 1, 2009): 492–505. http://dx.doi.org/10.5254/1.3548260.
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Abstract Physical blends and thermoplastic vulcanizates (TPVs) based on EPDM and PP were prepared in a batch mixer. Dynamic vulcanization of TPVs using resol/SnCl2 was studied as a function of time. Static and dynamic vulcanization of EPDM in the absence of PP were also studied. Crosslinking of EPDM in the absence of PP is more efficient via static than dynamic vulcanization. For EPDM/PP-based TPVs the extent of crosslinking reaction versus time decreases as the amount of EPDM increases. Degradation of the EPDM network occurs during dynamic vulcanization, due to the combined action of shearing and high temperature, and increases as EPDM becomes more and more the continuous phase.
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Grigoryeva, O., A. Fainleib, O. Starostenko, I. Danilenko, N. Kozak, and G. Dudarenko. "Ground Tire Rubber (GTR) Reclamation: Virgin Rubber / Reclaimed GTR (RE)Vulcanizates." Rubber Chemistry and Technology 77, no. 1 (March 1, 2004): 131–46. http://dx.doi.org/10.5254/1.3547806.
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Abstract Thermochemically partially devulcanized ground tire rubber (GTRD) was revulcanized in compositions with different virgin rubbers. Two different devulcanizing groups (mixture of softeners) with and without processing oil have been used for GTR treatment. As virgin rubbers methylstyrene/butadiene (SBR), isoprene (IR) and butadiene (BR) rubbers or their combinations were selected. They were cured by using sulfur, tetramethyl thiuram disulfide (TMTD) or peroxide based vulcanizing systems. The Rubber/GTRD (re)vulcanizates with the GTRD content from 20 to 80 wt. % have been prepared and studied. Vulcanization by sulfur system was found as preferable for IR/GTRD formulations. The best properties for BR/GTRD and SBR/GTRD vulcanizates were reached with the vulcanization system based on TMTD. The co-curing in the interphase between the GTRD particles and the surrounding rubber matrix improves the mechanical properties of (re)vulcanizates obtained. The reclaimed GTRD studied has been used successfully in standard formulations for tires instead of the part of virgin rubbers.
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Layer, Robert W. "Recuring Vulcanizates. I. A Novel Way to Study the Mechanism of Vulcanization." Rubber Chemistry and Technology 65, no. 1 (March 1, 1992): 211–22. http://dx.doi.org/10.5254/1.3538601.
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Abstract Vulcanizates, to which a curative is added by swelling, can be recured to easily study a variety of aspects of the vulcanization process, such as maturation, reversion, and even how much accelerator remains active as its zinc salt at the end of the cure. In effect, vulcanizates can be viewed as high-molecular-weight model compounds. In this study, we find that recuring SBR/BR vulcanizates, to which sulfur or the sulfur donor, N,N′ -dithiodimorpholine, is added, develops the same state of cure as the same amount of sulfur (or sulfur donor) added for the initial cure. This suggests that exchange reactions occur between crosslinks and the zinc-sulfur-accelerator complex during the cure and that all of the accelerator remains as its zinc salt at the end of the cure. This last result is interesting, since it is not consistent with the current view that most of the accelerator becomes irreversibly bound to the rubber and lost during the vulcanization of polybutadiene rubbers.