Synthetic Isoprene Rubber Research Articles

Predicting the Dynamic Characteristics of Vibration-isolating Rubbers Based on Natural and Synthetic Rubbers

The principal vibration-isolating characteristics of rubbers based on natural rubber and a combination of synthetic isoprene and butadiene rubbers were determined. The static and dynamic moduli, the hysteresis losses, and the logarithmic decrement were measured on an Yerzley mechanical oscillograph (manufactured by the US company Tavdi) in accordance with ASTM D-945. The changes in these characteristics were measured in the process of heat ageing. To convert the data to room temperature, the Arrhenius equation was used. The main changes in the static modulus occur in the first three years, and the main changes in the dynamic modulus in the first five years. Their ratio and the natural frequencies are different for various rubbers and for different storage and service times. The resonance zones are also different. It is concluded that, when predicting the useful life of the vibration isolator, it is necessary to assess all the dynamic and static parameters for each individual case.

Chlorinated Isoprene Rubbers in Adhesive Composites

Now there is not a single area of industry that can do without adhesive elastomer materials. Composites based on synthetic rubbers comprise 75% of the total volume of adhesive materials produced, which is due to the combination of unique properties typical of the elastomer base of the adhesive. The base of many imported adhesives for the bonding of rubber to metal is chlorinated natural rubber. As an alternative, chlorinated synthetic isoprene rubber has been proposed, developed at the Scientific Research Institute for Synthetic Rubber in St Petersburg. The chlorinated isoprene rubber was compared with imported chlorinated natural rubber in adhesive composites, and the physicomechanical properties of mixes based on a blend of chlorinated rubber and nitrile butadiene rubber were investigated. The investigation was conducted on chlorinated natural rubber of grade Pergut S20, chlorinated isoprene rubber SKI-3, and nitrile butadiene rubbers of grades BNKS-28AMN and SKN-26S. The influence of the ratio of chlorinated rubber to nitrile butadiene rubber and the technological factors of mix preparation on the properties of films produced from them was established. It was shown that, in terms of the level of properties, home-produced chlorinated rubber can be used as the base for adhesives for hot bonding of rubber to metal instead of imported Pergut S20.

Adhesive properties of rubbers with promoters based on modified silica filler

The influence of new adhesion promoters on the strength of bonding between unfilled rubber materials based on synthetic isoprene rubber SKI-3 and a brass-plated metal cord was studied. The synthesized adhesion promoters are silica fillers modified with cobalt, nickel, or a combination of cobalt and nickel, and they contain on their surface a lower number of ions of metals with variable valency compared to industrial cobalt stearate. It was shown that, among the synthesized adhesion promoters, silica fillers modified with cobalt are the most promising.

Determination of configurational–isomeric composition of synthetic isoprene rubbers using NMR spectroscopy

Production pieces of synthetic isoprene rubbers are studied using the nuclear magnetic resonance spectroscopy method. The measurements are performed by 1Н and 13С NMR spectroscopy with variation of the conditions of sample preparation and taking and processing of spectra, which allows improving the accuracy of quantitative analysis of the content of monomer units characterized by different configurations.

加硫ゴム表面にブリード・固着化させたワックスのオゾン遮断効果

Effect of wax on ozone degradation of vulcanized rubber was investigated at temperatures between -30 °C and 40 °C. The vulcanized rubber was prepared by mixing synthetic isoprene rubber with CB, sulfur, ZnO, stearic acid, accelerator and wax, followed by heating at 160 °C for 8 min. It was further heated at 23 °C, 40 °C and melting temperature of each wax for 72 hours under 20% stretching, in order to segregate the wax onto the surface of the vulcanized rubber as a bleeding. Ozone exposure tests of the vulcanized rubber were carried out at the temperatures between -30 °C and 40 °C in the presence of 50 pphm ozone for 24 and 168 hours, respectively. Crack propagation of the ozone-degraded rubber was observed with a digital microscope. The wax, bleeding onto the surface of the vulcanized rubber, was found to improve the ozone resistance of the rubber as compared with an ordinary bloomed wax.

The Morphology and Strength of Composites Based on an Isoprene Elastomer and Polyethylene, Modified with Fillers of Different Nature

An investigation was made of the effect of different additions of nanoparticles on the morphology, density, and strength of composites based on synthetic isoprene rubber (SKI-3) and low-density polyethylene (LDPE). The extremal dependence of strength and density on the concentration of nanoparticles was established.

Computational Experimental Studies on Magnetoelastic Effects in a Metal Filled Elastomer

The article presents experimental data from a study of the magnetoelastic effect in metal filled elastomers. The matrix material is a synthetic isoprene rubber and a functional filler is magnetite finely dispersed granules. The dependencies of the magnetic field near the sample on the strain and stress are given.

Effect of glycoluril and its derivatives on the flame resistance and physico-mechanical properties of rubber

The effect of bicyclic bisureas (glycolurils) and their derivatives functionalized with hydroxymethyl, halomethyl, and dimethoxyphoshorylmethyl groups on the flame resistance and physico-chemical properties of synthetic isoprene and divinyl rubbers was studied, and the procedures for preparing these agents were suggested. The rubbers with the addition of the synthesized bicyclic bisureas demonstrated satisfactory levels of flame resistance and physico-mechanical parameters.

The influence of adhesion promoters on elastic and strength properties and structure of elastomeric compositions

The effect of new promoters on the adhesion of elastic and strength properties unfilled elastomeric compositions based on synthetic isoprene rubber SKI-3 and also on the structure of their vulcanizates are investigated. Synthesized adhesion promoters constitute silica fillers modified with cobalt, nickel, and a combination of cobalt and nickel. They contain on the surface a reduced number (compared with industrial stearate, cobalt) ions of metals of variable valence. Tests are carried out to determine the dependency of changes of the tensile strength, the elongation at break and the density of the crosslinking of rubbers on dosages of the investigated adhesion promoters and amounts of metal ions on their surface. The effect of type and dosage of the synthesized promoters of adhesion of rubber to steel brassedcord on heat aging resistance of elastomeric compositions are established. It is established that the vulcanizates containing synthesized adhesion promoters have greater high temperatures resistance as compared with the rubber materials containing industrial cobalt stearate. Increasing dosages of modified silica acid fillers in elastomeric compositions, quantity of metals on their surface leads to the decrease of the resistance of vulcanizates to heat ageing. While Nickel ions have less oxidation effect on rubber, compared to cobalt ions that may be due to their lesser activity It is determined that the introduction of adhesion promoters leads to the formation of additional cross-linking. It is revealed that use the mineral promoters in the elastomeric compositions affects less the density of cross-linkage of rubber after heat aging as compared with the cobalt stearate. When administered in an elastomeric composition the silica modified nickel, increasing the crosslinking density of rubber upon exposure to elevated temperatures was observed.

Influence of the structure of organic peroxides on the efficiency of modification of SKI-3 rubber with dicarboxylic acid anhydrides in solution

The efficiency of modification of synthetic isoprene rubber with maleic and endic anhydrides in solution was examined as influenced by a number of initiator systems: dicumyl, dibenzoyl, and dilauroyl peroxides.

Study on Strain-induced Crystallization of Cross-linked Natural Rubber Revealed by Synchrotron X-ray

Characteristics of strain-induced crystallization (SIC) are described on sulfur cross-linked and peroxide cross-linked natural rubber (NR) and synthetic isoprene rubber (IR). Simultaneous tensile and wide-angle X-ray diffraction measurements using synchrotron radiation systems were carried out in order to elucidate SIC. The stretched molecular chains acted as initiating species of the crystallization, while surrounding chains contributed to the crystal growth. Stretching ratio at the onset of SIC (αc) decreased with an increase of network-chain density (ν) for peroxide cross-linked NR (P-NR), while it remained constant for sulfur cross-linked NR (S-NR). But, dependence of relative crystallization rates on ν was similar for both P-NR and S-NR. Calculated entropy differences between the undeformed and the deformed states at αc were equal for P-NR regardless of ν, whereas it became smaller with the increase of ν for S-NR. The SIC behavior of P-NR was in agreement with the prediction on homogeneous or uniform networks by Flory. Network in sulfur cross-linked IR (S-IR) was composed of domains of high ν value embedded in the rubbery network matrix, which gave a characteristic feature in its SIC. Mechanical propeties of S-NR and P-NR are also discussed from the viewpoint of their SIC behaviors on the basis of the network structures.

Isoprene rubber filled with silica generated in situ

AbstractWe modified synthetic isoprene rubber by means of the in situ generation of silica particles through the sol–gel process starting from tetraethoxysilane (TEOS) as an inorganic oxide precursor. Different reaction conditions were investigated with variations in the initial TEOS content, the reaction time of the sol–gel process, and the presence of a coupling/surfactant agent (octyltriethoxysilane). Organic–inorganic hybrid materials with a silica content up to 70 phr were obtained with the complete conversion of TEOS to silica for a long enough sol–gel reaction time. A very homogeneous dispersion of silica particles was observed in all cases together with a very good adhesion between the filler and matrix. The size of the in situ generated silica was controlled by the appropriate addition of octyltriethoxysilane. Swelling and extraction tests and dynamic mechanical analysis indicated that the vulcanization process of isoprene rubber was perturbed by the sol–gel process; this led to a slight decrease in the crosslinking degree. However, a significant reinforcing effect due to the presence of silica particles was observed for all of the investigated samples. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Development of technology for the production of microspherical alumina support for the alkane dehydrogenation catalyst: II. The influence of hydrothermal treatment conditions on the operational characteristics of microspherical alumina support and chromium oxide/alumina catalyst for the dehydrogenation of iso-butane

For the purpose of improving the mechanical strength and reducing the abrasive activity of micro-spherical chromium oxide/alumina catalysts for the processes of alkane dehydrogenation in fluidized bed, we have developed technology for the production of new highly durable boehmite support with the use of technical aluminum trihydrate as an initial raw material. The technology includes two consecutive stages: the dehydration of aluminum trihydrate and the subsequent hydrothermal treatment of dehydration product into boehmite. Part II covers the results on the influence of conditions for the hydrothermal treatment of aluminum trihydrate dehydration products in an industrial autoclave of special construction on the phase composition, physicomechanical and structural characteristics of boehmite support, the acidic properties of its respective oxide form and chromium oxide/alumina catalyst based on this support and also on the catalytic properties of this catalyst in the reaction of iso-butane dehydrogenation into iso-butylene. It has been shown that differently sized boehmite crystallites and also gibbsite are formed in the volume of microgranule under hydrothermal conditions of χ-Al2O3 dehydration depending on a chosen regime (temperature, time). For the production of iso-butane dehydrogenation selective chromium oxide/alumina catalyst with the minimal content of strong acidic sites, catalyzing the cracking reactions, it is necessary to provide such hydration conditions, under which large (43–47 nm) boehmite crystals are formed. The appearance of strong acidic sites is caused by small boehmite crystals and the presence of nonhydrated χ-Al2O3 phase. In the absence of the impurity gibbsite phase, the highly durable microgranules of boehmite support and catalyst are formed. The conditions, providing the complete χ-Al2O3 hydration into macrocrystalline boehmite, have been defined. The application of the developed two-stage technology gives the iso-butylene yield of 45–49%, the selectivity of 88–90%, and the abrasivity of 0.10 g/(m2 h). The given technology for the production of catalyst is realized in an industrial unit with the capacity of 100 t per month at OAO Karpov Mendeleevsk Chemical Plant (Mendeleevsk). Industrial catalyst lots are currently under operation at the Synthetic Isoprene Rubber Plant of OAO Nizhnekamskneftekhim.

Development of technology for the production of microspherical aluminum oxide supporter for the paraffin dehydrogenation catalyst

For the purpose of improving the mechanical strength and to reduce the abrasive activity of microspherical chromoalumina catalyst for the paraffin dehydrogenation in fluidized bed, technology, using technical aluminum trihydrate as an initial raw material and including consecutive stages of Al(OH)3 dehydration and hydrothermal processing of its product into boehmite, has been developed for the production of highly durable boehmite supporter. As applied to the iso-butane dehydrogenation into iso-butylene, microspherical chromoalumina catalysts, which are synthesized with the use of boehmite supporter, exceed their known industrial analogous in activity, selectivity and physicomechanical properties. The technology of supporter and iso-butane dehydrogenation catalyst is realized at OAO Karpov Mendeleevsk Chemical Plant (Mendeleevsk) for the production with the capacity of 100 t per month. Industrial catalyst lots are under operation at the Synthetic Isoprene Rubber Plant of OAO Nizhnekamskneftechim. The given article consists of two parts. In the first one, investigation results are presented for the changes in technical properties of Al(OH)3 during its dehydration in an industrial continuous baking drum-type furnace. The changes in physicomechanical characteristics of granules at the dehydration stage are caused by phase transformations of gibbsite and boehmite, by crystalline structure rearrangements in the volume of microgranules and do not depend on mechanical loads in a baking furnace and on porous structure changes. The conditions of gibbsite complete phase change into the two-phase boehmite-χ-Al2O3 mixture with minimal reduction in the microgranules strength have been determined: Tav = 435−475°C, νTHA = 170 kg/h, and τav = 0.8 h.

Cure Kinetics Study of Unfilled and Carbon Black Filled Synthetic Isoprene Rubber

Abstract The reversion type cure kinetic and induction time models were successfully utilized to predict the isothermal and nonisothermal evolution of the state of cure in vulcanization of the unfilled and carbon black (CB)-filled IR compounds measured by APA 2000. The rate constants for the reversion reaction and the formation of the stable and unstable crosslinks and the parameters of the induction time function with the Arrhenius temperature dependences were determined from the isothermal cure measurements. The equation was proposed to adequately describe the measured dependence of the difference between the maximum and minimum torques as a function of isothermal curing temperature. The measured induction time as a function of heating rate and step temperature variation was successfully predicted based on parameters of the isothermal induction time model. Isothermal cure modeling at each curing temperature individually or at all the curing temperatures simultaneously showed the excellent agreement with the experimental data for both curing and reversion. More severe reversion in the CB-filled IR in comparison with the unfilled IR was explained by comparing their reversion rate constants.

Continuous Ultrasonic Devulcanization: Comparison of Carbon Black Filled Synthetic Isoprene and Natural Rubbers

Abstract Continuous ultrasonic devulcanization of carbon black (CB) filled isoprene rubber (IR) was carried out. Similar to unfilled IR, power consumption during the devulcanization of the filled IR increased with the increase of ultrasonic amplitude indicating a greater extent of devulcanization. This was in contrast with the devulcanization of CB filled natural rubber (NR) where power consumption showed a maximum at an intermediate amplitude suggesting a lesser extent of devulcanization at higher amplitude. Such a behavior evidently resulted from the difference in the amount of stereoregular structures in the IR and NR rubbers. Gel fraction and crosslink density of the virgin vulcanizates, devulcanizates and revulcanizates were characterized. Kinetics of revulcanization, rheological properties of the devulcanizates and mechanical properties of revulcanizates were compared with those of virgin uncured IR and their vulcanizates. The effect of processing oil on the IR vulcanization, devulcanization and revulcanization was examined indicating a slight delay of the vulcanization and lower torque without affecting the degree of reversion. The addition of oil caused more devulcanization as indicated by an increase in the ultrasonic power consumption and a reduction of the gel fraction and crosslink density of devulcanized rubbers. The revulcanization of the IR occurred without the induction period, regardless of the presence of CB and processing oil. The retarder introduced in the recipe was effective in improving the scorch safety and minimizing the reversion in revulcanization. The experimental data on normalized gel fraction versus crosslink density of filled IR and NR at low CB loadings was found to fall into the master curve, which is probably determined by the main chain structure of both rubbers consisting of cis-1,4 isoprene. At high CB loadings, some differences were observed. The simulation results predicted such a behavior.

Study on Strain-induced Crystallization of Crosslinked Natural Rubber by Synchrotron Radiation

The characteristics of strain-induced crystallization (SIC) are described on sulfur-crosslinked and peroxide-crosslinked natural rubber (NR) and synthetic isoprene rubber (IR). Simultaneous tensile and wide-angle X-ray diffraction measurements using synchrotron radiation systems were carried out in order to elucidate SIC, the rate of which was much faster than so called cold crystallization of NR. Onset strain of SIC of sulfur-crosslinked rubber was almost independent of network-chain density. The stretched molecular chains acted as initiating species of the crystallization, while surrounding chains contributed to the crystal growth. Deformation of crystal lattice with nominal stress was detected, which showed the strain-induced crystallites were responsible for the higher modulus upon stretching. A pantograph model describes the deformation mechanism of the rubber network. The effect of non-rubber components of NR on SIC was clearly detected, where the stress relaxation after high speed stretching gave the significant difference of SIC between NR and IR. Stearic acid did not accelerate SIC of sulfur-crosslinked NR and IR, oppositely with the cold or temperature-induced crystallization of them. The effect of carbon black filler on SIC of sulfur-crosslinked NR is also reviewed. For peroxide-crosslinked NR, SIC occurred when the deformation brought about a definite entropic state, this agrees with the theoretical prediction by Flory and is consistent with the classical theory of rubber elasticity.

Ultrasound devulcanization: comparison of synthetic isoprene and natural rubbers

Sulfur-cured vulcanizates of unfilled synthetic isoprene rubber (IR) were prepared and successfully devulcanized in a continuous co-axial ultrasonic reactor. Die pressure characteristics and ultrasonic power consumptions were measured. Network structures of the virgin vulcanizates, devulcanizates and revulcanizates were characterized by gel fraction and crosslink density according to the classic swelling method. The molecular characteristics of the sol generated by ultrasound treatment were determined by GPC. Kinetics of revulcanization, rheological properties of the devulcanizates and mechanical properties of the revulcanizates were compared with those of virgin uncured IR and their vulcanizates. In addition, a comparison of the cure behavior, devulcanization characteristics, network structures and the mechanical properties was made between IR and the natural rubber (NR) reported earlier. Simulations on the correlation of the normalized gel fraction and the normalized crosslink density show that these two rubbers have almost equivalent probability of main chain scission and crosslink rupture ratio, which is probably determined by the main chain structure of both rubbers consisting of cis-1,4-isoprene.

Structural and mechanical study of elastomers under plane deformation

The plane shrinkage of various elastomers [natural rubber, synthetic isoprene rubber, and plasticized poly(vinyl chloride)] at room temperature has been studied via direct microscopic observations. Prior to deformation, the surface of polymer samples is decorated with a thin (several nanometers) metallic layer. Further deformation leads to formation of the surface relief in the coating. An analysis of the formed microreliefs allows one to visualize and characterize the induced stress field in the sample. The shrinkage of poly(vinyl chloride) samples is accompanied by development of the uniform surface relief over the whole surface of the deformed polymer. This fact suggests a homogeneous character of the stress field and, hence, a homogeneous structure of the polymer sample. In the case of crosslinked rubbers (natural rubber and synthetic isoprene rubber), their plane shrinkage leads to the development of an irregular pattern on the polymer surface. In addition to the folded surface relief that is typical of the poly(vinyl chloride) structure, one can observe 20-to 50-μm “islands,” which are characterized by their own morphological features. Information on structural inhomogeneity of rubbers that is obtained by scanning electron microscopy correlates with the data of DSC measurements. The advantages of electron microscopic procedure for studying structural rearrangements in polymers during strain recovery of elastomers are demonstrated.

Biodegradable Protein-Containing Elastomeric Vulcanizates

Abstract The effects of leather powders, chrome tanned leather powders and keratin were studied on properties of the synthetic isoprene rubber IR and the microbiological decomposition of the resulting proteinous-elastomeric composites. The proteins were obtained from the waste of the leather industry. The incorporation of proteins into the mixes of synthetic 1,4-cis-polyisoprene provides increased recaptivities to microbiological decomposition.