SKI-3 Rubber Research Articles

INFLUENCE OF THE FRACTIONAL COMPOSITION OF SHUNGITE AND ITS COMBINATION WITH MINERAL MICROFIBERS ON THE PROPERTIES OF RUBBERS

The influence of the fractional composition of shungite from the Zazhoginskoye field (Republic of Karelia) on the kinetic, elastic-strength properties, linear combustion rate, and erosion resistance of rubber based on synthetic isoprene rubber SKI-3 was studied. The effectiveness of using a combination of mineral fillers (shungite and kaolin microfibers) to increase the resistance of rubbers to erosion entrainment under the influence of high-temperature gas flows is shown.

STUDY OF PROPERTIES OF ISOPRENE OLIGOMERS OBTAINED BY MICROWAVE IRRADIATION OF SKI-3 RUBBER

The present article proposes a method for production of low molecular weight rubber in microwave irradiation field. Isoprene rubber SKI-3 (10% solution in toluene) was used as the initial reactant. The effect of MWI power change (144 W, 450 W, 675 W, 900 W) on the degree of destruction was studied. The degree of destruction was measured based on the change in viscosity average molecular weight. The findings of the experiment data analysis indicate that the destruction process occurs in correspondence with the following dependency: the increase in the microwave irradiation power raises the destruction degree. At the same time, a decrease in molecular weight was observed. Furthermore, it was found that the use of phospholipids as modifiers also affects the destruction process. The increase in phospholipids content in toluene-SKI-3 system reduces the degree of polyisoprene destruction regardless of the microwave irradiation power. It is demonstrated by the fact that rubber molecular weight is subject to a lower decrease in systems with higher phospholipids content. Phospholipids perform two functions. Firstly, they act as a stabilizer that inhibits the rubber destruction process. Secondly, varying their content allows controlling the destruction degree and obtaining oligomers with predetermined molecular weight. The obtained oligomers were used as SKI-3 isoprene rubber modifiers. It is observed that that the introduction of oligomers into rubber mixtures in the amount of 7 and 10 parts by weight per 100 parts by weight of rubber increases its cohesive strength. Furthermore, vulcanizates containing oligomers are characterized by improved physical and mechanical properties.

Research of Structure and Properties of Rubber Mixtures with Adhesion Additives on the Basis of Carbamide

The effect of new adhesion promoters on the bond strength of rubber compounds with rubber cord based on synthetic isoprene rubber SKI-3, as well as on the structure of their vulcanizates, is investigated. The synthesized additives were taken as adhesion promoters: 2,4-diphenylcarbamidotoluene (DPKT); 2-isocyanatophenylcarbamidotoluene (IPCT) and the industrial promoter is Manobond 680C. Tests were conducted to determine the adhesion strength to the metal cord and the density of the cross-linking of the obtained rubber compounds by the dosage of additives. It is determined that the maximum value of adhesion had mixture containing 1.2 parts by weight of 2-isocyanato-phenylcarbamidotoluene and Manobond 680C. It was found that the introduction of additives DPCT and IPCT leads to the formation of additional cross-links in the vulcanizates. Rubbers containing additives in an amount of 0.4-1.2 parts by weight have the highest density of crosslinking. The studies made it possible to hypothesize the relationship between the particle size and the electrokinetic potential of blocked urea-based isocyanates with the strength of brass-metal cord-rubber bonding. The results obtained indicate that the greater the electrokinetic potential of the synthesized additives and the lower the average particle size, the better the additive is distributed in the rubber compound and affects the formation of the adhesive layer at the brass-metal cord-rubber interface.

Modified Silica Filler as a Promoting Agent of Adhesion of Rubber to Metal Cord

In order to increase the strength of the adhesive bonding of rubber based on SKI-3 rubber substance to metal cords, the effect of adhesion-promoting agents, which are silicic filler modified by metal ions of variable valency (Co and Ni), has been investigated. It is shown that such adhesion-promoting agents do not have a significant effect on the technological and physicomechanical properties of rubber at room temperature, but increase the resistance of vulcanizates to elevated temperatures (up to 100°C) and increase the strength of the rubber–metal cord connection under the influence of aggressive factors in the process operation of metal cord products.

New Antiozonants for Rubber Compounds Based on Oxyalkylated Derivatives of 4-Aminodiphenylamine

This paper sets out the properties and the results of the testing of new antiozonants 2PPD and 3PPD in place of standard and imported 6PPD and IPPD which are used in the production of mechanical rubber goods and tyres (in the sidewall, tread, and other elements). The proposed method for producing the new antiozonants makes it possible to organise their industrial production by low-cost technology, in contrast to 6PPD and IPPD production technology. The raw materials for the new antiozonants include ethylene and propylene glycols, available in Russia, and 4-aminodiphenylamine, imported for the production in Russia of antioxidant S789, which is widely used in the production of large-tonnage rubbers, in particular synthetic isoprene rubber SKI-3, over 70% of the volume of which is exported. A number of advantages of 3PPD over imported stabilisers have been established. These include a greater effectiveness in protecting rubber compounds against thermal oxidation and ozone cracking by comparison with the stabilisers it is replacing. The shortcomings of the new antiozonant (in terms of the form in which it is produced and in terms of its influence on the vulcanisation kinetics) are considered, and various ways to overcome these shortcomings are presented.

An Investigation of the Effect of Taurit Filling of Rubber Mixes for the Coating of Radial Lorry Tyre Breakers

The results of investigating the effect of the shungite analogue Taurit (grade TSD) on the properties (measured on an RPA 2000 instrument) of a breaker rubber mix and of a rubber compound based on synthetic isoprene rubber SKI-3 are set out. Different methods of introducing Taurit have been tested: 10 parts into the rubber at the stage of its production; 10 parts into the standard rubber mix at the first stage of mixing; 10 parts into the rubber subjected to preliminary mechanical plasticisation in a laboratory internal mixer at a temperature of 100°C. The introduction of Taurit into the rubber in small quantities in order to reduce the proportion of rubber constituent in the rubber mix has also been tested. The test results have been compared with results for standard rubber mixes and rubber compounds. When Taurit is introduced into rubber at the stage of its production, the cohesive strength of the rubber mix and the rate of its vulcanisation and also the dynamic modulus components G′ and G″ are increased. When Taurit is introduced into plasticised rubber, again G′ and G″ are increased, there is an increase in plasticity, and the elastic recovery of the rubber mix is reduced. The breaker rubber compound from this mix has the best adhesion to metal cord and the highest dynamic strength. Data on the Payne effect indicate a better carbon black particle distribution when Taurit is introduced into the rubber at the stage of its production. Reduction in the proportion of rubber constituent in the rubber mix leads to a deterioration in the carbon black particle distribution.

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.

The Effect of New Antiagglomerators of the Quantislip Series for Solution-Polymerised Rubber on the Properties of cis-1,4-polyisoprene

The results of pilot-plant tests of SKI-3 isoprene rubber containing a series of Quantislip™ rubber crumb antiagglomerators (AAs) are presented. Tests were conducted at OAO ‘Sintez Kauchuk’, with the AAs introduced at the degassing stage. The new Quantislip AAs, developed by OOO ‘NPP Kvalitet’, ensure a reduction in calcium and chlorine ions in wastewater and in its alkalinity. An improvement in the elastic strength properties of carbon-black-filled vulcanisates based on cis-1,4-polyisoprene (SKI-3) and containing AAs was shown. For the production of SKI-3 rubber, an optimum AA composition – Quantislip of grade BM-2R – was developed. When BM-2R is used, stearic acid, formed in standard rubber with a calcium stearate suspension as AA, is eliminated. The possible mechanism of improvement in the strength properties of carbon-black-filled vulcanisates based on SKI-3 is discussed. This is possibly due to an improvement in rubber–filler interaction as a result of there no longer being any competition between segments of macromolecules and stearic acid for active centres when carbon black is adsorbed on the surface.

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.

Simple and low-cost method for processing of waste from production of 2,6-di-tert-butyl-4-methylphenol to give a high-efficiency stabilizer of rubbers and biodiesel fuel

Technologically simple and low-cost method is suggested for processing of wastes from manufacture of ionol, a resin from the rectification stage, by isolation of 4,4′-ethylenebis(2,6-di-tert-butylphenol) via dissolution in hexane with the subsequent crystallization. A high activity of the product as a stabilizer of SKI-3 rubber and biodiesel fuel was demonstrated.

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.

Synthesis of polyfunctional sulfur-containing oligomers and their effection SKI-3 rubber and its vulcanizates

Polysulfide oligomers with sterically hindered phenolic fragments were prepared. Their effect on the antioxidative stability and kinetics of vulcanization of rubber stocks based on SKI-3 rubber was examined.

Characteristics of the Stabilising Action of Phenolic Antioxidant 4,4'-Bis(2,6-Di-Tert-butylphenol) in the Ageing Processes of Rubbers

T/41 4,4ʹ-Bis(2,6-di-tert-butylphenol) (BP) is of great interest to scientists and practitioners on account of its high stabilising effectiveness in processes of ageing of carbonchain polymers, primarily elastomers. In all probability it can be assumed that the high potential of the stabilising action of BP is connected with its ability readily to be oxidised to 3,3ʹ,5,5ʹ-tetratert-butyl-4,4ʹ-diphenoquinone (DPQ) under conditions of thermal oxidation of polymers with the formation of an equilibrium system and with subsequent participation of the products of transformation in the inhibition of the thermo-oxidative degradation of polymers [1]. With the aim of obtaining experimental proof of the proposed hypothesis, it was of interest to conduct a comparative study of the anti-oxidative activity of BP and DPQ, and also model mixtures based on BP and DPQ, under conditions of ageing of rubbers. Investigations were conducted under standard conditions adopted in factory practice at the Nizhnekamskneftekhim Open Joint Stock Company. Specimens of butyl rubber, SKI-3 polyisoprene rubber, and SKD-N polybutadiene rubber containing the investigated and industrial antioxidants were oxidised in hot air at 140°C for 90 min (for SKI-3) and 120 min (for SKD-N and butyl rubber). The indices of retention of the properties of the rubber were the values of the Mooney viscosity and elastic recovery 60 s after the viscometer rotor had stopped [2]. Testing of butyl rubber specimens under ageing conditions showed (Table 1) that the greatest effectiveness is exhibited by BP which in its stabilising properties is superior to industrial antioxidant 2,2ʹ-methylenebis(4methyl-6-tert-butylphenol) – AO-2246 – which is currently used at Nizhnekamskneftekhim. DPQ is markedly less effective than antioxidants BP and AO-2246 in stabilising the physicomechanical properties of butyl rubber. It was shown that, for rubber SKI-3 (Table 2), both BP and DPQ are effective stabilisers, and also mixtures based on them. These stabilisers ensure retention of the physicomechanical properties of SKI-3 at the level of the amine antioxidant Dusantox-1 widely used in industry, and they perform considerably better than phenolic antioxidant AO-2246. The index used in evaluating the stabilising properties of antioxidants in SKI-3, characterising the viscosity gradient over a prescribed period from the start of rotor rotation J, again indicates the effectiveness of the stabilisers investigated (see Table 2): reduction in this index corresponds to an increase in the antioxidative stability of the rubber [2]. Physicomechanical tests of SKD-N also showed the high effectiveness of the antioxidants investigated (Table 3). In the presence of individual DPQ, the Mooney viscosity of SKD-N rubber hardly changed under ageing conditions. Industrial AO-2246 proved to be considerably less effective in the stabilisation of SKD-N than DPQ, BP, or their mixtures. Kauchuk i Rezina, No. 3, 2006, pp. 17–19

Polyfunctional complex sulfur-containing additives to SKI-3 rubber and vulcanizates thereof

The performance of new polyfunctional additives containing bis(2,6-di-tert-butyl-4-hydroxyphenyl) polysulfide and dicyclopentadiene-sulfur copolymer was studied with respect to SKI-3 and vulcanizates thereof. These additives act not only as stabilizers but also as vulcanizing agents improving a number of physicomechanical characteristics of the vulcanizates.

New oligomeric thioether antioxidants for polymers

Polyfunctional oligomeric antioxidants with a sterically hindered phenolic fragment were prepared. The influence of these antioxidants on oxidation and degradation of SKI-3 rubber was analyzed.

Salts of sulfaminic and nitrosulfonic acids — their synthesis and thermal transformations

A crystalline potassium salt of sulfaminic acid and some fractions of amorphous potassium salts of nitrosulfonic acids were obtained from a nitro-oligomer of the polyisoprene rubber SKI-3 by treating it with potassium hydrogensulfite. Crystalline Ba, Pb, Cd and Mg salts were also obtained. Their behavior on dynamic heating in air and nitrogen was also studied. The crystalline salts under study as well as the free sulfaminic acid were found to have similar thermal transformations and considerable thermal stability: they retain their weight up to about 300°. Some of these salts are crystal hydrates and are dehydrated in the temperature range 110–150°. The initial decomposition temperature of the free sulfaminic acid according to the DTA curve is 230°. The principal decomposition of amorphous potassium salts begins above 200°, showing endothermal effects between 250 and 300° and exothermal ones at about 300 and 410°. The composition and the constituent functional groups of the obtained salts were determined using elementary and thermal analysis, as well as IR spectroscopy and chemical methods.

Change in the optical properties of ski-3 rubber in deformation, fatigue, and thermal and radiation aging

Optical methods can be used in studying the kinetics of mechanical fatigue, thermal, and radiation aging; some general characteristics and differences in the development of these processes in elastomers with higher extinction can be detected with them. The sensitivity of the measurements is increased by the rational selection of the light wave-length of preliminary homogeneous biaxial stretching. A decrease in the thickness attained by deformation by one order of magnitude did not convert the optical medium to the class of singly scattering media, but the changes in the optical properties in aging were more pronounced against the background of decreasing extinction.

Efficiency of antiozonants under conditions of static load. Dependence on deformation, content of the additive and ozone concentration

The influence of uniaxial elongation (10 to 160%) on the efficiency of various antiozonants was studied in radiation and sulphur-crosslinked synthetic rubber SKI-3 (poly- cis-1,4-isoprene). The activity of the antiozonant was evaluated from the time dependence of stress. The experimental data are explained by assuming that the antiozonant fulfils two simultaneous functions by reacting with ozone and participating in the formation of a protective surface layer.

Kinetics of the growth of cracks on polyisoprene vulcanizates in ozone

The kinetics of growth of cracks on synthetic polyisoprene SKI-3 rubber vulcanizates in ozone has been studied by optical microscopy. The mean value of crack surface is used as a measure of the degree of cracking. The growth of crack surface comprises two stages; namely, a relatively slow one at the beginning of the process and a faster one which proceeds at a constant rate. Empirical dependences which describe this process at various ozone concentrations are suggested. A physical interpretation of the constants in these expressions is presented.