Synthetic Isoprene Rubber Research Articles

Natural and synthetic isoprene rubbers obtained using Ziegler–Natta catalysts

Objectives. To compare the properties of rubber compounds and rubbers based on natural rubber RSS1 and synthetic isoprene rubbers obtained using Ti, Nd, Gd catalysts, both when used individually in the formulation of rubber compounds and when synthetic analogues partially replace natural rubber.Methods. Rubber compounds were prepared using a laboratory roll and a 100 cm3 rubber mixer. For rubber compounds, the following factors were determined: Mooney viscosity, cohesive strength, and vulcanization characteristics. For rubbers, the following factors were determined: physical and mechanical parameters, Shore A hardness, rebound resilience, and volume loss upon abrasion.Results. Based on the results of the rubber compound tests, the study showed that compounds based on all the synthetic polyisoprenes studied are significantly inferior to compounds based on natural rubber in terms of cohesive strength. The partial replacement of natural rubber with synthetic rubber (regardless of the type of catalytic system) leads to a significant decrease in the cohesive strength of the blends. Despite the differences observed in the properties of the rubber compounds, the results of the rubbers based on individual rubbers do not manifest significant differences.Conclusions. The study demonstrated the influence of defects (oligomers, gel, low molecular weight fractions, branches, and 3,4-units) in the structure of synthetic polyisoprenes on the cohesive strength index of rubber compounds based on them, in which the number of 3,4-units plays a decisive role. The study also showed the potential of studying synthetic polyisoprenes as analogues of natural rubber in formulations of rubber compounds in the aims of resolving the problem of import substitution in the tire and rubber goods industry.

Confinement of Oligopeptides by Terminally Functionalized Polyisoprene to Improve Their Mechanical Strength, Creep Resistance, and Antifatigue Properties.

A small amount of terminal polar phase endows natural rubber (NR) with excellent comprehensive properties superior to those of synthetic isoprene rubber. In this work, the comprehensive properties of synthetic rubber were remarkably improved by introducing a stable terminal nanoconfinement structure by combining terminal hydroxyl groups and pentapeptide molecules noncovalently into the same phases. The results show that the stable terminal phases hardly affect the free chain motion but enhance the entanglement. Under cyclic loading, the terminal polar phases undergo hierarchically structural changes such as reversible dissociation of the weak bonds, phase deformation, and crystalline reorganization, all of which dissipate the stress and are beneficial for high strength and extensibility. At the same time, synthetic rubbers demonstrate much superior fatigue resistance and lower hysteresis relative to NR and maintain comparable dimensional stability. This strategy suggests that the comprehensive properties of elastomers can be regulated and upgraded by facile terminal noncovalent interactions.

Investigation of dielectric parameters of structural nanocomposites based on polyethylene

The dependence of the dielectric constant and specific volume resistance of a structural composite based on (80 wt%) synthetic isoprene rubber and (20 wt%) low density polyethylene on the content of nanosized particles of aluminum fillers, Nalchikin and carbon black in small quantities is shown graphically. Using an electron probe method for studying the microstructure of a structural material, a hydrostatic weighing method based on determining the density of a composite by its double weighing and an electron shadow microscope, this paper presents models and physical mechanisms that lead to extrema in the permittivity and conductivity of composite materials.

Synergistic effect of cuttlebone particles and non‐rubber components on reinforcing ability of natural rubber and synthetic isoprene rubber composites

AbstractThe comparison of the reinforcing ability of cuttlebone (CTBO) particles in natural and synthetic isoprene rubber (NR and IR, respectively) composites were investigated. The CTBO particles could reinforce in both NR and IR composites. However, the improvement of tensile properties in CTBO‐filled NR composites was higher than that of IR composites due to the presence of non‐rubber components in NR. The non‐rubber components promoted the strong interfacial adhesions with filler and rubbery matrix to increase the bound rubber content. These results affected the increase of the stress softening degree, hysteresis loss, residual strain during cyclic deformation and the volume fraction of constrained rubber region (immobilized area of rubber) in CTBO‐filled NR composites. The atomic force microscopy evidently revealed good compatibility between the CTBO particles and the NR matrix due to the presence of organic components from CTBO particles and from non‐rubber components in NR. Accordingly, the CTBO particles and non‐rubber components play important roles in improving the properties of green rubber composite materials.

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.

INFLUENCE OF MICROSPHERES ON PROPERTIES OF AGGRESSIVE RESISTANT RUBBERS

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.

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.

Parameterization of the structures arising in the deformation of elastomers

The phase structure of synthetic isoprene rubber samples subjected to stretching was studied by transmission electron microscopy. A procedure for determining the fractal dimension of extended one-dimensional structures arising during deformation was proposed. Image parametrization, being the extraction of substantial acting parameters, their description, and quantitative estimation of the obtained parameters, made it possible to characterize each stage of the deformation. A combination of standard methods of studying electron microscopic images using the fractal theory to describe the supramolecular and phase structures of elastomers allows one to understand the mechanism of the deformation process and the nature of the structures arising in structure rearrangement.

PROCESSING–PROPERTY RELATIONSHIPS IN WHEAT PROTEIN–UNVULCANIZED ISOPRENE RUBBER COMPOSITES

ABSTRACT An optimized set of processing parameters was determined for trypsin hydrolyzed gliadin protein (THGd, from wheat) and unvulcanized synthetic isoprene rubber (IR) composite compounds. The compounding temperature, time, and shear dependency of the THGd:IR compounds were investigated with rheology, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). Individual protein aggregates measuring ∼64 × 280 nm, with a length-to-width aspect ratio of ∼4.3, were agglomerated within the IR matrix, as measured in SEM-EDX micrographs. A higher compounding temperature (T = 150 °C) was favorable for good protein aggregate dispersion and deagglomeration, which resulted in IR reinforcement, as demonstrated by up to a 65% increase in storage modulus (G′). The tan δ was lowered by the addition of the THGd protein to IR, indicating less mechanical energy was lost as heat in the composites. As the compounding speed, that is, shear rate, was increased from 30 to 60 rpm at constant temperature (T = 150 °C), the average agglomerate size and G′ were minimally affected, but the loss tangent (tan δ) was increased, indicating an increase in IR degradation with shear rate. By drying the THGd hydrolysate at a slower rate or to a greater solids content, the composite G′ was increased and tan δ was decreased. In the slow-dried THGd hydrolysate, protein aggregates were less resistant to breakup during processing, indicating that the protein preparation was an important processing parameter.

Adhesive Compounds Based on Chlorinated Polyisoprenes

Adhesive compounds based on chlorinated natural rubber of foreign (Pergut S20) and domestic chlorinated polyisoprene (Cl-SKI-3 and Cl-SKI-5) production are investigated for a compound rubber based on a NBR-26 nitrile butadiene rubber–St3 connection. The optimum solvent for the fabrication of adhesive compounds based on chlorinated isoprene rubbers is determined using a thermodynamic approach. The resistance of chlorinated natural rubber (Pergut S20) and synthetic isoprene (Cl-SKI-3 and Cl‑SKI-5) rubbers to the action of high temperatures is determined via TGA and DSC. The possibility of the use of domestic chlorinated polyisoprenes based on SKI-3 and SKI-5 rubbers for the industrial production of elastomeric adhesives is shown.

Hydrolyzed wheat protein as a self-assembled reinforcing filler in synthetic isoprene rubber vulcanizates

Trypsin hydrolyzed gliadin (THGd) from wheat protein is utilized as a reinforcing filler in synthetic rubber. THGd self-assembles into a reinforcing filler phase during sulfur vulcanization of synthetic cis-1,4-polyisoprene rubber (IR), as observed by an increase in the β-sheet aggregation absorbance in Fourier transform infrared (FTIR) spectroscopy. The curing process is studied using differential scanning calorimetry (DSC). THGd filler interferes with the curing process resulting in more incomplete cure and a reduced induction time. Young’s modulus (E) increases with protein concentration, curing time, and silane coupling agent concentration. Moduli comparable to or greater than the IR Control are achieved at all tested protein loadings of 4–16 parts per hundred rubber (phr). Hysteresis decreases with curing time showing the formation of a more elastic network and increases with filler and silane concentration showing energy dissipation through filler re-arrangement and rubber molecule-filler particle detachment, respectively. Reduced swelling is observed with the addition of silane coupling agent as there are more protein-rubber interactions. The results suggest that quantities of THGd greater than 4 phr reinforce the rubber phase through continued aggregation into protein β-sheet nanostructures.

Agricultural proteins as multifunctional additives in ZnO‐free synthetic isoprene rubber vulcanizates

ABSTRACTCorn zein and wheat gliadin protein are compounded into synthetic cis‐1,4‐polyisoprene rubber (IR) and sulfur‐cured in a zinc oxide (ZnO)‐free system. The curing kinetics and mechanical and morphological properties are compared to a ZnO‐activated or carbon black (CB)‐reinforced cure system. The proteins provide reversion resistance and reinforcement to IR at filler loadings as low as 1 part per hundred rubber (phr). The zein‐IR composites exhibit higher moduli, better filler–matrix adhesion, and less filler agglomeration/migration than gliadin‐IR because zein is more chemically compatible with IR. The gliadin‐IR composites have a lower percent set and hysteresis, indicating the formation of an elastic restoring gliadin network. Optimal properties are achieved at 2‐phr gliadin and 4‐phr zein. At gliadin loading >2 phr and zein loading >4 phr, the protein domain size increases and mechanical properties deteriorate. At equal filler loading, property improvements over CB‐IR are observed for one or both proteins. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48141.

The Viscosity Effect of Masticated Natural vs. Synthetic Isoprene Rubber on Toughening of Polylactic Acid

This study investigated the different viscosity effects of natural isoprene rubber (NR) compared to the synthetic one (IR) on toughening of polylactic acid (PLA). Here, 15 wt% rubber was melt blended with PLA in an internal mixer at 180°C and 50 rpm. It was found that the addition of these rubbers led to a significant increase in the tensile toughness and impact strength. These rubbers were masticated at 50°C and at 200 rpm for various mastication times to reduce their molecular weights. A too-long mastication time was found to adversely affect the impact strength and tensile toughness due to the fast agglomeration of rubber particles. At a comparable viscosity, it was remarkable that the impact strength of PLA/NR was higher than that of PLA/IR regardless of the similar chemical structures probably because the presence of nonrubber components including proteins and lipids could enhance the interfacial interaction between NR and the PLA matrix.

Effect of modified keratin from renewable sources on composites properties of synthetic isoprene rubber

The present conducted research focused on elastomeric materials containing reinforcing modified keratin fibers in their composition. The applied keratin was modified by solvolysis reaction to obtain the product in the form of a hydrolysate. Then, the hydrolysate was modified by the addition reaction of keratin adduct with a plasticizer—technical stearin is commonly used in processing elastomers. The keratin hydrolysate adducts were used in a different weight proportion in the composites in which the carrier was isoprene rubber (IR; Cariflex 305). The obtained composites (rubber Cariflex composites (RC)) were subjected to a series of tests aimed at understanding the structure and interactions between biopolymers and other components of elastomeric mixtures. Mechanical properties, including hardness, the cross-linking density, and thermo-oxidative aging were investigated. Microbiological tests were carried out, which in turn allowed to determine the effect of introduced keratin in a modified hybrid form, to the elastomeric matrix. The test results indicate a significant improvement of some properties, especially when using 10 parts by weight of keratin adducts introduced into 100 parts by weight of IR rubber.

A Study of the Dielectric Permittivity and Specific Volume Resistance of Synthetic Isoprene Rubber and Polyethylene Composites Containing Carbon Soot and Aluminum Nanoparticles

The dependences of dielectric permittivity and specific volume resistance of an 80% ISR-3 + 20% LDPE composite on the concentration of aluminum and carbon soot nanoscale particles are studied in this work. These curves are considered. When concentrations of Al and soot nanoparticles are low in the composite, the e' = e′(C) and ρV = ρV(C) curves, which do not fit the Maxwell–Wagner polarization model, are significantly changed.

Signals of Isotopomers in 13C NMR Spectra of Polyisoprene Rubbers

Analysis of 13C-satellites was carried out in the 13C NMR spectra of isoprene rubbers with a natural content of 13C carbon isotope. 13C-satellites are the signals caused by the one-bond spin–spin coupling of 13C nuclei. The spin–spin coupling 1J(13C–13C) constants, as well as the magnitude of the effect of the isotopic substitution 1Δδ13C(13/12C), were measured under magnetic shielding of 13C nuclei. The results indicate that the configurational and local conformational structure of natural and synthetic isoprene rubbers is identical.

Role of strain rate in the strain-induced crystallization (SIC) of natural and synthetic isoprene rubber

The role of strain rate ( $${{\dot \varepsilon }}$$ ) in the strain-induced crystallization (SIC) of vulcanized natural rubber (NR) and synthetic isoprene rubber (IR) was studied using in situ wide-angle X-ray scattering (WAXS) (synchrotron X-ray radiation). We developed homemade extension equipment and coupled it with the synchronized time-resolved X-ray detector system. The nucleation rate (I) was determined for a wide range of $${{\dot \varepsilon }}$$ values (0.0075 s−1–330 s−1) based on the increase in the scattering intensity (IX) as a function of time (t). We found that I is proportional to $${\dot{\varepsilon }}$$ ( $$I \propto \dot \varepsilon$$ ). Based on this result, we concluded that $$\dot \varepsilon$$ plays an important role in the kinetic mechanism of the SIC of NR and IR. The role of strain rate ( $$\dot \varepsilon$$ ) in strain induced crystallization (SIC) of vulcanized natural rubber (NR) and synthetic isoprene rubber (IR) was studied by in-situ wide angle X-ray scattering (WAXS). The nucleation rate (I) was determined by measuring the slope on the plot of the scattering intensity (IX) as a function of time (t). Various I values were determined for various $$\dot \varepsilon$$ . On the plot of I vs. $$\dot \varepsilon$$ , we found that I is proportional to $$\dot \varepsilon$$ ; I ∝ $$\dot \varepsilon$$ .

Experimental characterization and analytical modeling of a large-capacity high-damping rubber damper

This study explores the mechanical response of a high-damping rubber damper (HRD) under different loading conditions. HRD is a typical viscoelastic damper that consists of 2 layers of elastomer compound sandwiched between 3 steel plates. The elastomer compound used in this study is a synthetic isoprene rubber reinforced with carbon black and designed to provide high damping capacity with relatively low stiffness. Four damper specimens with a displacement capacity of 75 mm at 300% shear strain were fabricated. Each damper was subjected to harmonic loading to investigate the effects of strain amplitude, loading frequency, strain history, and cyclic loading on the mechanical properties of HRD. Hysteretic force–displacement loops for each loading condition were plotted, and the variations of maximum damper force, equivalent stiffness, storage shear modulus, dissipated energy, loss factor, and equivalent viscous damping ratio with different test parameters were examined. In addition, an analytical model capable of simulating behavior of HRD at various strain amplitudes and loading frequencies was proposed. The experimental results indicate that the developed HRD can provide a damping ratio ranging from 15% to 43% under different loading conditions and has relatively stable hysteresis loops under cyclic loads. In addition, the energy dissipation capacity of the damper significantly increases when the loading frequency is over 0.5 Hz without an increase in stiffness.

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.