Butadiene Rubber Vulcanizates Research Articles

Synergistic effect of a new binary accelerator system on curing characteristics and properties of styrene–butadiene rubber vulcanizates

Synergistic effect of a new binary accelerator system on curing characteristics and properties of styrene–butadiene rubber vulcanizates

Preparation and Characterization of Activated Palm Kernel Shell/Carboxylated Nitrile Butadiene Rubber (APKS/XNBR) Vulcanizate

Malaysia is one of the most important palm oil producers and exporters in the whole wide world. There has been a rapid development of new palm oil plantations and palm oil mills in this country. The palm oil industry plays a vital role in the economic growth of Malaysia. However, as the palm oil industry grows bigger and wider, a huge amount of palm oil waste is produced which is an alarming issue considering it can cause pollution and have a negative effect on the environment. Raw Palm Kernel Shell (PKS) derived from palm oil waste can be converted into Activated Palm Kernel Shell (APKS) which has the potential to be a value-added biofiller in rubber vulcanizates. Thus, in this study, APKS is prepared through a carbonization process at a temperature of 900 °C and an activation process via steam treatment and used as filler in Carboxylated Nitrile Butadiene Rubber (XNBR). The aim of this study is to evaluate the influence of different loading ratios of APKS on theswelling index measurement, bound rubber content (BRC), abrasion resistance, compression set, and hardness of XNBR vulcanizates. APKS is incorporated in XNBR at different loading ratios, ranging from 0 to 50 phr and these APKS-filled XNBR vulcanizates are prepared with a two-roll mill. The overall physico-mechanical properties of APKS-filled XNBR vulcanizates showed increment in terms of BRC, compression set, and hardness as the loading ratio of APKS increased. XNBR vulcanizates with a higher loading ratio of APKS also showed a decrease in swelling index measurement and volume loss which would indicate high abrasion resistance. These results could be attributed to the porosity of APKS as shown in the morphological analysis which provided a high surface area of contact for crosslinking and mechanical interlocking. This proves APKS could potentially be a semi-reinforcing filler for rubber vulcanizates, especially for XNBR vulcanizates as XNBR vulcanizates were able to achieve high abrasion resistance and high hardness with the incorporation of APKS. With this, the conversion of PKS into APKS could help to reduce palm oil waste and provide an environmentally friendly, sustainable biofiller option to rubber researchers and manufacturers who are looking for an alternative to petroleum-based fillers. This would be very beneficial for both the palm oil industry and the rubber industry.

A comparative study for the main properties of silica and carbon black Filled bagasse-styrene butadiene rubber composites

A comparative study has been done to investigate the effect of carbon black (CB) and fumed silica (Si) on the physico-mechanical and thermal properties of Bagasse/styrene-butadiene rubber (B-SBR) composites. Based on the incorporation of 25 phr from natural ground bagasse powder (GBP) as a supplement reinforcing filler in styrene butadiene rubber (SBR) vulcanizates, two identical sets of formulations have been prepared using different concentrations (20, 40, 60 and 80 phr) of carbon black and silica as the main reinforcing fillers in SBR composites. The ground bagasse powder (GBP) employed in this work, has a selective grain size distribution ranging from about 20–180 μm. As well, 2.5 phr of maleic anhydride (MA) was incorporated to improve the interfacial adhesion between SBR and bagasse. The distinguishing effect of different fillers on the rheological properties was clearly established. Tensile strength, elongation at break, modulus at 100% elongation (M 100), hardness (Shore A), abrasion loss, degree of swelling, as well as, thermal gravimetric analysis (TGA) of the rubber vulcanizates were studied. The prepared samples were morphologically analysed by scanning electron microscopy (SEM). The tensile strength and M 100% values of carbon black-filled compounds were obviously higher than those of the silica filled ones. In addition, hardness, wear and swelling properties were improved more and more by increasing the filler content. Whereas, the Si filled B/SBR showed a decreasing trend in elongation at break values but with an evidently higher plateau than that of CB filled ones. Overall, the CB filled vulcanizates recorded dominant mechanical properties compared to the Si filled vucanizates. On the other hand, both fillers offered a noticeable improvement in thermal stability, but with a preference favored for the silica filled compounds. Furthermore, the findings for SEM were found to be in agreement with the observed mechanical properties. This study summarizes a detailed discussion of the emerging green technologies for tyre production and depicted comprehensive data from the available literature.

Payne effect and Mullins effect of silica filled butadiene rubber nanocomposites vulcanizates and their unextractable gels

Rubber nanocomposites exhibit strain softening under large-amplitude oscillation shear and large-strain cyclic tension while the mechanisms remain unresolved. Herein we systematically investigate the Payne effect and Mullins effect of unfilled and silica filled butadiene rubber (BR) vulcanizates to clarify the impacts of crosslinking density, sol fractions, and filler content. During large-amplitude oscillation shear, the critical strain amplitude for the onset of Payne effect is closely related to storage modulus in the linear viscoelastic region. During cyclic tension deformations, the recovery hysteresis energy and accumulating softening energy are involved in the local deformation of the rubber matrix, which is promoted by the filler phase. These findings are illuminative for optimizing performance of rubber nanocomposite products by controlling the nonideal network structure of viscoelastic rubber matrix.

Nonlinear viscoelastic behavior and their time-temperature superposition for filled styrene butadiene rubber compounds and vulcanizates

The nonlinear viscoelastic behavior of rubber composites is of great practical importance in their processing as well as the application. In this paper, nonlinear viscoelastic behavior for vulcanized and unvulcanized filled styrene butadiene rubbers (SBR), SBR/carbon black (CB) composites, were mainly investigated. Besides the conventional Payne effect, frequency (ω) sweep tests at different strains (linear and nonlinear viscoelastic regions) were performed to get more information about viscoelastic response, especially in nonlinear region that close to actual driving conditions. Conductivity synchronization test was also operated to explore the evolution of CB agglomerates. It reveals that the filler network structure recovers slowly but the rubber network recovers rapidly during an increasing and decreasing strain sweep cycle. At large strain, rheological parameters of vulcanizates change significantly with increasing ω. A pseudomaster curve based on the ω sweep at large strain and different temperature can be obtained both for compounds and vulcanizates, indicating that the time-temperature superposition is also applicable to the nonlinear viscoelastic behavior. Similar linear and nonlinear viscoelastic behaviors of filled vulcanizates to that of unfilled vulcanizates demonstrate the same mechanism of viscoelastic response. The loss modulus peak of filled vulcanizates primarily comes from the Rouse movement of rubber chains between crosslinking points. Under large strain, the strain amplication effect of particles hardly influence the characteristic relaxation time of Rouse movement between crosslinking points.

Fly Ash from Lignite Combustion as a Filler for Rubber Mixes. Part I: Physical Valorization of Fly Ash.

The potential use of fly ash (FA) originating from lignite combustion at the Belchatow Power Plant (Poland) as filler for rubber mixes was evaluated. Samples of fly ash collected from heaps created in different years were compared according to their chemical and phase composition, particle size distribution, and morphology. The sieve fractionation of fly ash results in size fractions of different chemical structures, phase compositions, and morphologies, reflected in changes to their specific surface area, surface energy, and activity in rubber mixes. Fractionation turned out to be more effective than grinding from the point of view of using ash as a filler for rubber mixes, because it results in higher specific surface area (SSA) and chemical composition differentiation. Carbon black can be replaced by up to 40% by weight with the fly ash fraction (FFA) of dimensions below 125 µm, without any significant deterioration in the mechanical properties of styrene butadiene rubber (SBR) vulcanizates filled with 50 phr of active carbon black (N 220). Despite the larger fly ash fraction of grain dimensions in the range between 125 and 250 µm presenting the highest specific surface area, the particle size adversely affects its strengthening effect in rubber. Taking into account all the tests performed, ranging from morphology, Payne effect and bound rubber, to mechanical and abrasion tests, the highest potential effectivity is presented by a sample containing 30 phr of N 220 and 20 phr of FFA of grain sizes from 63 to 125 µm. The obtained results indicate that fractionation seems to be an effective physical method of fly ash valorization.

The application of nano silica as a potential, cost-efficient green filler in acrylonitrile butadiene rubber vulcanizates containing carboxy-terminated liquid natural rubber

The challenge of sustainable development demands renewable natural sources. Natural rubber is one of the major plantation crops in the equatorial region, where there is a tremendous scope for tapping solar energy. The carboxy-terminated liquid natural rubber (CTNR) was commercially prepared by the sunlight irradiation of a solution of maleic anhydride and masticated natural rubber. Carboxy-terminated liquid natural rubber (CTNR) can be used as a polymeric plasticizer in acrylonitrile butadiene rubber (NBR) vulcanizates. As a reinforcing filler in rubber products, bio compatible green silica is rapidly replacing carcinogenic carbon black. This paper describes the cost-effective application of eco-friendly nano silica, which can improve the tensile properties, rebound resilience, compression set, ageing and oil resistance and reduce the heat build-up of the NBR vulcanizates. The properties of nano silica–filled NBR vulcanizates containing CTNR (NS NBR -CTNR) were compared with those containing amorphous silica. The enhancement in properties, exhibited by NS NBR-CTNR vulcanizates, may be attributed to the increased bound rubber content resulting from the large surface area of the nano-sized filler. The superior retention of properties after ageing and oil extraction shown by NS NBR-CTNR vulcanizates may be due to the better rubber filler interaction, ionic crosslinking and co–cross-linking of CTNR to NBR. The use of a combination of a conventional plasticizer and CTNR in nano silica–filled NBR is found to be promising.

Enhanced performance of cellulose nanofibre reinforced styrene butadiene rubber nanocomposites modified with epoxidised natural rubber

The present work focuses on the potential use of Pandanus kaida proproot cellulose nanofibre as reinforcing filler for styrene butadiene rubber (S) vulcanizates in the presence of epoxidised natural rubber (E) as modifier. The incompatibility between the polar cellulose and non-polar styrene butadiene rubber can be overcome by the use of epoxidised natural rubber (E). This is a facile process compared to other strategies where cellulose nanofibers are chemically modified thus making the process expensive. Initially, cellulose nanofibre was extracted from Pandanus kaida prop root via hydrothermal assisted oxalic acid hydrolysis. FESEM image revealed that cellulose nanofibres (PN) had a diameter of around 15–30 nm. S/PN masterbatches were prepared via latex stage mixing, co-coagulated, later melt-mixed with E and other compounding ingredients followed by vulcanisation. The investigation of mechanical properties revealed that PN nanofiber at 5 phr loading (S/PN5) resulted in enhanced properties. For further improvement, epoxidised natural rubber (E) was used as modifier at various loadings in S/PN5. At 1 phr of E loading (S/PN5/E1), the tensile strength, modulus, tear strength and abrasion resistance index improved significantly by 150%, 47%, 93% and 19%, respectively, compared to S gum vulcanizates. Strain sweep studies indicated better fibre-matrix interaction in the presence of E1. DMA studies revealed a higher storage modulus, lower damping, higher cross-link density and lower adhesion factor for S/PN5/E1 composites.

Relationships between properties and rapid gas decompression (RGD) resistance of various filled nitrile butadiene rubber vulcanizates under high-pressure hydrogen

We evaluated the crosslink density, permeability, tensile properties, hardness of NBR vulcanizates, featuring different fillers and contents, and correlated the properties of the filled nitrile butadiene rubber (NBR) vulcanizates with their resistance to rapid gas decompression (RGD). Also, we investigated the relationship between the relative change in the properties of filled NBR vulcanizates, induced by exposure to high-pressure hydrogen, and their RGD resistance. The crosslink density, tensile strength, hardness of filled NBR vulcanizates, the associated solubility coefficient, as well as the resistance of the filled NBR vulcanizates to high-pressure hydrogen increase with increasing filler content while the RGD resistance, elongation at break, permeability coefficient of the filled NBR vulcanizates, as well as the associated diffusivity coefficient of hydrogen decrease. These results indicate that the properties of NBR vulcanizates are closely related to their resistance to high-pressure hydrogen. The properties of filled NBR vulcanizates are impaired by exposure to high-pressure hydrogen, regardless of filler type and content, and the relative change in their elongation at break and volume is related to their RGD resistance. In addition, the properties and resistance to high-pressure hydrogen of HAF and silica-filled NBR vulcanizates are superior to those of MT-filled NBR vulcanizates. Therefore, HAF and silica-filled NBR vulcanizates are more suitable for application in high-pressure hydrogen facilities. Additionally, the compatibility of filled NBR vulcanizates can be estimated to some extent through relative change in elongation at break and volume resulting from exposure to high-pressure hydrogen.

Influence of coagents on Payne effect of butadiene rubber vulcanizates

Gum vulcanizates exhibit Payne effect and weak strain overshooting behavior, which is usually forgot in rubber industry. Herein the Payne effect of butadiene rubber (BR) vulcanizates is investigated for clarifying the effect of crosslinking density and sol content mediated by using coagent in conjugation with dicumyl peroxide. Toluene extraction and paraffin swelling of the vulcanizates are performed for clarifying the contribution of sol fraction and chains entanglement. The results show that the Payne effect and weak strain overshooting of gum vulcanizates are closely related to effective crosslinking density rather than network defects. This work is helpful for understanding the nonlinear rheological responses of the gum vulcanizates with defective network structure.

Rheological and Mechanical Properties of Silica/Nitrile Butadiene Rubber Vulcanizates with Eco-Friendly Ionic Liquid.

In this paper we designed greener rubber nanocomposites exhibiting high crosslinking density, and excellent mechanical and thermal properties, with a potential application in technical fields including high-strength and heat-resistance products. Herein 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) ionic liquid was combined with silane coupling agent to formulate the nanocomposites. The impact of [EMIM]OAc on silica dispersion in a nitrile rubber (NBR) matrix was investigated by a transmission electron microscope and scanning electron microscopy. The combined use of the ionic liquid and silane in an NBR/silica system facilitates the homogeneous dispersion of the silica volume fraction (φ) from 0.041 to 0.177 and enhances crosslinking density of the matrix up to three-fold in comparison with neat NBR, and also it is beneficial for solving the risks of alcohol emission and ignition during the rubber manufacturing. The introduction of ionic liquid greatly improves the mechanical strength (9.7 MPa) with respect to neat NBR vulcanizate, especially at high temperatures e.g., 100 °C. Furthermore, it impacts on rheological behaviors of the nanocomposites and tends to reduce energy dissipation for the vulcanizates under large amplitude dynamic shear deformation.

High permittivity ceramics-filled acrylonitrile butadiene rubber composites: influence of acrylonitrile content and ceramic type

Influence of acrylonitrile content and ceramic type on cure characteristics, mechanical, morphological, and dielectric properties of acrylonitrile butadiene rubber (NBR) vulcanizates was examined. Two types of ceramic filler, namely barium titanate (BT) and calcium copper titanate (CCTO), were synthesized by solid-state reactions. The ceramic powders were then characterized by X-ray diffraction, particle size analyzer, and scanning electron microscopy (SEM). Ceramic/rubber composites were then mixed in an internal mixer at 60 °C and a rotor speed of 60 rpm. Two acrylonitrile contents of NBR, namely 33 wt% and 42 wt%, were tested. Incorporation of ceramic fillers in NBR matrix and increasing acrylonitrile content shortened scorch and cure times, but increased minimum, maximum, and delta torque. Furthermore, SEM results revealed that the BT-filled NBR composites showed better filler–matrix interactions than the CCTO-filled NBR composites. This matches the better mechanical and dielectric properties of the BT-filled NBR composites.

PERFORMANCE EVALUATION OF HYPERELASTIC MODELS FOR CARBON-BLACK–FILLED SBR VULCANIZATES

ABSTRACTThe performance of four recently developed hyperelastic material models (HM models) was evaluated by using stress–stretch relationships of filled styrene butadiene rubber vulcanizates with different contents of carbon black (CB) tested under uniaxial tension (UT), pure shear (PS), and equi-biaxial tensile (BT) conditions. The stress–stretch relationships for the PS and BT tests were obtained with a specially designed specimen having higher accuracy than those obtained with an ordinary specimen. The performances of the HM models were compared via the following three evaluations: (1) ability to reproduce the UT, PS, and BT tests; (2) ability to predict the PS and BT test results with material constants identified from the UT test; and (3) correlation between the identified material constants and CB contents. The evaluations based on a combination of the stress–stretch relationships with high accuracy and four recently developed HM models revealed that the HM model activates only the I1 term, which is the first invariant of the right Cauchy–Green tensor, exhibiting good reproducibility and predictability.

Synthesis of 2-Alkylbenzimidazole moiety as a novel antioxidant and its effect on physico-mechanical and electrical properties of acrylonitrile butadiene rubber

In the present work, 2-propyl-, and 2-heptyl-, 1H-benzo[d]imidazole were prepared by condensation reaction of o-phenylenediamine with n-butanoic acid and n-octanoic acid, respectively. The prepared products were characterized by FT-IR, 1H-NMR spectroscopy and melting point. These products were incorporated into acrylonitrile butadiene rubber (NBR) composites with two different fillers (Silica and High Abrasion Furnace carbon black HAF) as an antioxidant additive with different concentrations from 1up to 2 phr as a comparison with 2,2,4-trimethyl-1,2-dihydroquino-line (TMQ) as a traditional antioxidant. Their effects on the rheometric, physico-mechanical and electrical properties of NBR composites were evaluated. Thermo-oxidative aging was carried out for NBR composites and distribution of the prepared products observed by Scanning Electron Microscope (SEM).The results showed that the prepared products can act as highly efficient antioxidants in acrylonitrile butadiene rubber vulcanizates comparing with commercial antioxidant TMQ and revealed that there was enhancement in mechanical properties of NBR composites that containing the prepared products, as well. The results also illustrated that the optimum ratio from 2-alkylbenzimidazole incorporated into acrylonitrile butadiene rubber vulcanizates is 1.5 phr if compared with the same ratio from traditional antioxidant (TMQ).

Cradle-to-cradle approach to waste tyres and development of silica based green tyre composites

This work is about simultaneous devulcanization and chemical functionalisation of waste styrene butadiene rubber vulcanizate (SBR) using thermo-mechanical treatment and sulphide based multifunctional devulcanizing agent. The as-grown compounds are reinforced with nano-silica and re-vulcanized to prepare rubber composites. The curing and processing characteristics, and mechanical performance are further compared with those of conventional silica based green tire formulations. The extent and quality of devulcanized rubber are monitored through the measurement of sol content, inherent viscosity of sol fraction, cross-link density and degree of devulcanization as a function of cross-link density. By our method based on restoring the curing and other processing parameters, the revulcanized composites offer ∼11 MPa tensile strength, ∼26 MPa tear strength together with elongation at break value as much as 450 %. Such values are comparable with those of the composites consisting of the associated fresh components of the systems. Surprisingly, the higher storage modulus and lower tan⁡δ of SBR-devulcanized SBR-silica composite as compared with standard counterpart sample (SBR-silica composite) confirms magnificent dynamic mechanical performance of the composites. This work may pave a new route for reuse of waste tyre in tyre production.

The rheometric, mechanical and morphological properties of carbon black filled styrene butadiene rubber vulcanizates in presence of alkanolamide

Properties of carbon black (CB)-filled styrene-butadiene rubber (SBR) vulcanizates include rheometric, mechanical and morphological in presence of alkanolamide were studied. The synthetic rubber was filled by CB at a settled loading at thirty parts per hundred rubber (phr). The alkanolamide was derived from ethanolamine and refined bleached deodorized palm stearin and it was incorporated into CB-filled SBR at one, three, five and seven phr. From the results, it was found that alkanolamide was a rubber chemical as a co-curing and plasticizing material. As a co-curing material, it reduced the times to cure and scorch of filled SBR vulcanizates. As a plasticizing material, it reduced minimum torque or viscosity but raised the elongation at break. The properties of torque difference, tensile moduli, hardness, tensile strength and resilience of CB-filled SBR vulcanizates were also raised due to the presence of alkanolamide. The presence of a five phr of alkanolamide was the optimum concentration for CB-filled SBR whatever was tested by morphological study. The fractured vulcanizate of CB-filled SBR with the five phr of alkanolamide demonstrated greatest surface roughness and matrix tearing.

Influence of Ionic Liquids on Structure and Rheological Behaviors of Silica-Filled Butadiene Rubber

Nanoparticle dispersion is important for the performance of rubber compounds. Herein, ionic liquids (ILs) and silane are used to prepare silica-filled butadiene rubber vulcanizates. The results show that replacement of a half of silane by ILs could greatly improve the dispersions of silica and zinc oxide, restrain the migration of sulfur and other additives inside the composite, and maintain the cross-linking degree of the matrix possibly by suppressing the adsorption of sulfur and other additives by silica. The regulated filler dispersity and matrix cross-linking strongly influence the dynamic rheological behaviors of the vulcanizates as a function of silica volume fraction. In comparison with silane, the introduction of ILs could improve the reinforcement effect, reduce energy dissipation, and lower the frequency dependences of loss modulus and loss tangent in the linear region.

High scission of butadiene rubber vulcanizate under thermo-oxidation

The cross-linked structure of butadiene rubber (BR) vulcanizate presents a challenge to the environmentally benign recycling of waste tires. The high scission of BR vulcanizate was realized by thermo-oxidation in the presence of soybean oil. The effects of the mass ratio of rubber to oil (2:1, 1:1, 2:3, 1:2 and 2:5), oxidation time (0.5, 1, 2, 3, 5, 7 h) and temperature (130, 140 and 160 °C) on degradation were investigated by measuring the evolution of the sol fraction and cross-link density of degraded BR. The results showed that the BR vulcanizate was degraded effectively under thermo-oxidation (140 °C, 3 h), resulting in the highest sol fraction of 70.7%. Furthermore, the structural evolution of degraded BR was studied by gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR). Oxidation, scission and recombination of the cross-linked network of BR occurred simultaneously during thermo-oxidation. The scission of the BR vulcanizate was enhanced by suppressing the recombination of BR chains in the presence of soybean oil.

Energy dissipation accompanying Mullins effect of nitrile butadiene rubber/carbon black nanocomposites

Mullins effect of carbon black filled nitrile butadiene rubber compounds and vulcanizates during cyclic tensile deformation is investigated and the influences of thermal annealing of the stretched samples, the deformation velocity and history and the solvent swelling are discussed. The energy losses associated with recovery hysteresis and softening accompanying the Mullins effect at a given crosshead velocity are quantitatively analyzed. The results show that the recovery hysteresis involves in microscopic deformation of the rubber phase in the nanocomposites but it disappears in the swollen samples. On the other hand, the softening is associated with both the rubber and filler phases; its energy loss increases with increasing filler content and decreases significantly by swelling. Furthermore, the softening of samples stretched at room temperatures is recoverable after conditioning at 80 °C but the recovery is retarded significantly by filler. The investigation allows gaining recognition of the important role played by the viscoelastic rubber matrix and the influence of the filler.

Dynamic Moduli Mapping of Silica-Filled Styrene–Butadiene Rubber Vulcanizate by Nanorheological Atomic Force Microscopy

Atomic force microscopy (AFM) offers nanoscale mapping of materials’ properties. Especially, our modified AFM termed “nanorheological AFM” enables us to measure the accurate frequency-dependent storage and loss moduli and loss tangent over a sixth-order frequency range without any temperature control at nanoscale resolution. These dynamic properties obtained by nanorheological AFM can be compared with those using bulk dynamic mechanical analysis (DMA) measurements. In this paper, we applied this technique to silica-filled styrene–butadiene rubber (SBR) to investigate the nature of the interfacial rubber region existing between a rubber matrix and silica particles at different temperatures. The dynamics properties of the interfacial rubber region were different from those of matrix rubber regions. The master curve obtained by this technique perfectly coincided with that by bulk DMA. Furthermore, it was found that the behavior of bulk loss tangent could be predicted by the contributions from both matrix and...