Rubber Compounds Research Articles

Effect of Shea butter as plasticizer on natural rubber-carbon black reinforced composites

This paper presents the effect of eco-friendly plasticizer, Shea butter oil (SBO) in rubber compounding involving Carbon black (CB)-filled Natural rubber (NR). The SBO based compounds (SBC) was systematically investigated and the results were compared with compositions prepared with Petroleum-based oil (PO). Although, some of the measured properties were comparable between SBC and POC, however, the SBC generally exhibited better properties compared to the POC. For example, the SBC coded NS5: (NR-50 parts per hundred parts of rubber (phr) CB-5phr SBO) and NS40 (NR-50 phr CB-40 phr SBO) obtained 7 and 17% greater than NT5 (NR-50 phr CB-5phr PO) and NT40 (NR-50 phr CB-40 phr PO), respectively, based on 300 and 100% modulus ratio (M300/M100). In terms of reinforcement measured by bound rubber content, BR (%), NS5 and NS40 recorded higher BR (%) of 9 and 48% than NT5 and NT40, respectively. The NS5 > NT5 by 12 and 7% in terms of crosslinking density and rebound resilience, respectively. Also, the NS5 > NT5 and NS40 > NT40 by 40 and 75%, respectively, in terms of fatigue life behavior. Such enhancement has been linked to successful distribution of the CB particles assisted by SBO within the matrix of NR. While the SBO is economical and has high potential to substitute the PO which is already suspected to be carcinogenic and environmentally unfriendly, SBO has exhibited good plasticizing effect for rubber compounding, especially as curing activators for recipe intended for manufacturing rubber articles.

Influence of functionalized S–SBR on silica–filled rubber compound properties

Styrene–butadiene–Rubber, SBR, is most often used in tread compounds in order to improve the Rolling Resistance (RR). The functionalized SBRs are used to increase the polymer–filler interaction in the compound to improve RR. In this study, the effect of different types of functional groups in SBR was investigated. Several types of functionalized S–SBR’s were synthesized by anionic polymerization: (i) SBR with an amine group at one end of the polymer chain, (ii) SBR with an alkoxy silane group at one end (iii) SBR with an amine group at one end and an alkoxy silane group at the other end of the polymer chain. A model reaction of silanization was conducted in a solvent to estimate how the amine functional group affects the silanization. Silica filled compounds were prepared with these SBR types. Payne effect and bound rubber measurement were done. The model silanization reaction of TESPT (Bis(triethoxysilylpropyl)tetrasulfide) with silica in the presence of amine shows that a higher amount of ethanol (EtOH) is released from TESPT compared to the amine free system. This result indicates that the silanization reaction can be accelerated by the presence of an amine functional group at the SBR polymer chain used in silica–filled compounds. The amine functionalized SBR and the alkoxy silane functionalized SBR show less Payne effect of the compounds which indicates that both functional groups can decrease the filler–filler interaction. More chemical bound rubber was obtained in branched SBRs compared to the corresponding linear SBRs. A branched polymer chain has a higher molecular weight compared to the linear type. Therefore, when one branched polymer chain reacts with silica or creates a silica–silane–polymer bond, more bound rubber can be obtained for the branched than for the linear type. The compound of the SBR with the alkoxy–silane functional group shows lower tan δ compared to the non–functionalized SBR and the amine functionalized SBR compounds. The influence of the type of functionalization of the SBR on tan δ at 70 °C was more significant in branched SBRs than in linear SBRs, due to the before–mentioned effect of the functional group on silanization and bound rubber.

Elucidation of the role of ZnO in sulfur cure in novel EPDM-CTS blends

A new concept is introduced in this study, suggesting the role played by the ZnO crystal in sulfur crosslinking polymers, particularly, rubber blends of EPDM-CTS. The study is conducted in a polymer blend of ethylene propylene diene terpolymer (EPDM) and cyclic tetrasulfide (CTS). CTS is a reactive low molecular weight polymer, which can act as a sulfur donor. It is proposed that the sulfur crosslinking occurs at the surface of the ZnO crystals. A reaction site is created on the surface of the ZnO crystal by the reaction with stearic acid, which creates a “template” or active site on the surface as a catalytic site for the CTS reaction to take place. Various experiments are performed to substantiate the newly proposed role the crystalline ZnO structure plays in influencing the initiation of the sulfur crosslinking. The investigation is conducted in rubber compounds in the absence of fillers and other additives and additionally in chemical model studies. The analyses conducted in rubber compounds are performed on fully or partially cured rubber to study the evolution of the chemical process involved in the CTS reaction and the curing of the rubber blends. Step-cured compound allows analyses of the transformation of the ZnO crystal size during the sulfur crosslinking process, and the ability to gauge the step transformation that the ZnO crystal is undergoing during the crosslinking process. Additional chemical model studies are used in the study of the influence of the ZnO crystal on sulfur crosslinking, to confirm the reaction path and by-products of reaction. Lastly, quantum mechanical (QM) and molecular mechanics (MM) calculations are applied in support of the suggested mechanism of reaction.

Effect of Wet Mixing on Properties of Radial-Orientation Basalt Fiber-Reinforced Rubber Compounds.

The effects of wet mixing and traditional mixing on the properties of radial-orientation basalt fiber-reinforced rubber products were studied through experiments. The results show that compared with traditional mixing, the basalt fibers under the wet mixing conditions can more effectively enhance the physical and mechanical properties of composites. The properties of the composites, such as carbon black dispersion, filler dispersion, rolling resistance and wet-sliding resistance, were the best after the latex and carbon black were premixed and then mixed by a mixer. Through extrusion experiments with the developed short-fiber radial-orientation die, it can be found that the fluidity of composites after extrusion is enhanced. Through analysis utilizing an electron microscope, it is shown that when the BFs added with KH550 (3-Aminopropyltriethoxysilane) were modified by KH560 ((3-Glycidyloxypropyl)trimethoxysilane), the interface layers of BF (basalt fiber)–KH560–NR and BF–KH550–NR were formed, which improves the adhesion between BFs and the rubber matrix. Qualitative characterization experiments on the orientation direction of the vulcanized composites were carried out through the experiments; that is, the qualitative characterization experiments on the segmented cutting and vulcanization of the composites in the radial direction showed that the short-fiber radial-orientation die could greatly improve the radial orientation degree of the short fibers in the radial direction. After adding KH560, the performance of the composites reinforced by the short fibers was improved to a certain extent compared with those without KH560. By adding DZ (N,N-Dicyclohexyl-2-benzothiazolsulfene amide) and CTP(cytidine triphosphate disodium) into the vulcanization system, the curing process of compounds in mixing and extrusion was delayed and the scorching resistance of short-fiber-reinforced composites was enhanced. Under the same conditions, the properties of the compounds after extrusion were greatly improved compared with those without extrusion.

Waste of brewing production - a coagulating agent in the technology of extraction of emulsion rubbers from latex

Today, there is a growing interest in the production of synthetic polymers, which are widely used in the production of modern materials. Of particular interest is the manufacture of rubbers by emulsion polymerization. Rubber compounds and vulcanizates made on their basis have characteristics due to which they are actively used in various industrial sectors. The coagulation process in the production of emulsion polymers increases environmental stress. Sodium chloride used at some enterprises as a coagulating agent is consumed in large quantities - up to 200 kg / t of rubber, and increases environmental pollution. In the presented work, for the first time, the possibility of recycling the beer production residue - inactivated yeast, which is proposed to be used to reduce the aggregative stability of disperse systems, is considered. The introduction of yeast into the emulsion polymer isolation technology makes it possible to reduce the amount of sodium chloride in the waters discharged from the enterprise. The use of a system based on a protein coagulant contributes to the complete release of coagulum from latex at a consumption of inactivated yeast in the amount of 10-15 kg/t of rubber. The most effective results were obtained when yeast preliminarily acidified with sulfuric acid was used in this process, which led to the charging of the nitrogen atom of the protein component. It is noted that the best temperature regime for the process of coagulation of latex particles is 1-20 ℃. An increase in temperature to 60 ℃ leads to an increase in the consumption of coagulant up to 25 kg/t of rubber. The ratios of the consumption of sulfuric acid and acidified yeast have been optimized, allowing to obtain the most complete coagulation of the latex. It has been established that the rubbers isolated using food production waste meet the requirements for rubbers of the SKS-30ARK brand according to the main physical and mechanical indicators.

A green dual-phase carbon-silica nanohybrid derived from black liquor lignin for reinforcing styrene-butadiene rubber

In rubber industry, lignin has been investigated as a potential alternative of fossil-derived carbon black (CB) for several decades. However, due to poor dispersity, big particle size and incompatibility with rubber, lignin cannot achieve the same reinforcing effect as CB by direct dry mixing. Here, a new and green dual-phase carbon-silica nanohybrid (LDPCS) was successfully prepared from black liquor lignin (BLL) and sodium silicate through a simple co-gelation/self-assembly and carbonization process. The preparation mechanism and process as well as the morphology and properties of LDPCS were investigated and discussed in detail. The results indicated that the hydroxymethylation and silane modification of BLL could improve its affinity with SiO2 sols, thus facilitating the co-gelation of BLL and SiO2 sols to inhibit the growth of SiO2 particles. During subsequent acid precipitation, silane modified hydroxymethylated BLL (SiHM-BLL) was self-assembled around SiO2 particles to form nanosized SiHM-BLL-SiO2 hybrids. After carbonization, SiHM-BLL-SiO2 nanohybrids were converted into LDPCS with small primary particle size of 60–90 nm, high specific surface area of 82.19 m2/g, relatively loose secondary aggregation structure and graphitic microcrystals in the carbon framework. With incorporating LDPCS into styrene-butadiene rubber (SBR) by direct dry mixing, LDPCS showed a superior reinforcing capability for SBR as compared with CB, which was ascribed to the nanoscale dispersion of LDPCS, robust C/SiO2 interfaces and high affinity with SBR matrix. This work provided a new insight into the fabrication of novel hybrid nanofiller from lignin and broadened the potential applications of lignin in rubber compounds and beyond.

Composition and processing influence on the performance of graphene-containing SBR/BR rubber compounds

Composition and processing influence on the performance of graphene-containing SBR/BR rubber compounds

QUEST FOR SUSTAINABLE CURATIVES FOR CHLOROPRENE RUBBER: A COMPREHENSIVE REVIEW

ABSTRACT Chloroprene rubber (CR) is one of the most versatile synthetic rubbers suitable for numerous industrial applications. For years, zinc oxide (ZnO) has been satisfactorily used as the vulcanization activator for CR, typically with organic accelerator(s). Ethylene thiourea (ETU) is the most widely used accelerator, offering the best balance between cost and performance in CR vulcanizates. Recently, the ZnO level in rubber compounds has become a pressing issue because of its harmful environmental impacts. ETU is classified as a substance of potentially serious health risks. It is therefore imperative to identify sustainable crosslinking additives for CR from both technical and commercial standpoints. The key purpose of this review is to collate the significant lines of technological advances made to identify proecological curative options for CR and update the information up to the current year. In preparation for this review, pertinent scholarly articles on the curing of CR, published in scientific journals mainly in the past two decades, were assessed. Since the scope of this review is to capture the significant technical information available in the public domain, the reference list is therefore not necessarily an exhaustive one. Reports dealing with proprietary chemicals or undisclosed technical strategies are beyond the purview of this review.

Developing a Rubber basedNanocomposite

Polymer compounds such as Natural Rubber (NR), which consists of compounds such as isoprene, are capable of being processed for the manufacture of a range of rubber based products for a large variety of applications. The properties of a natural rubber compound are susceptible to enhancements in their properties through the incorporation of nanofillers into its matrix. This study addresses the preparation of a natural rubber based nanocomposite that utilizes graphene as a nanofiller for the facilitation of the required enhancement in the rubber compounds properties. The nanocomposite specimens used in the study were prepared by means of acid-coagulation. The acid-coagulation formulation utilized was adapted from methodologies employed in commercial applications. The enhancement in the rubber properties due to the incorporation of the nanofiller was validated by means of mechanical testing. Prior to the testing, the applicable standard for tensile property testing was identified to be ASTM D412. Through the acclaimed standard, a mould to facilitate the preparation of the required specimens was 3D printed from PETG. The primary aim of the study was to determine the effect of large concentrations of graphene (beyond 2.5wt %).The results from the mechanical testing of the acid-coagulated samples exhibited enhancements in the elongation at break and tensile strength between unfilled NR and the graphene filled NR nanocomposite. With the incorporation of 5wt% of graphene, the elongation at break of the rubber increased to 687%, showing a 25% increase. The tensile strength of the rubber increased to 4.07 MPa, showing an enhancement of 102% in comparison to the pristine rubber compound. KEYWORDS: Natural Rubber, Graphene, Acid-Coagulation, Tensile strength, Elongation at break.

Analysis of tire wear airstrip particles (TWAP)

Tire wear is a main contributor to microplastics. As we cannot fully avoid tire wear, otherwise we could not brake and stop, new solutions are needed to address this problem. Not only on roads tire wear is released to the environment, even more can be found at airports. The advantage there is that the Tire Wear Airstrip Particles are gathered while cleaning the pavement. This collection is an opportunity to recycle and add new value to it. Whereas rubber powder is a common way to recycle and reuse end-of-life-tires as raw material in rubber compounds, the question is if TWAP is reusable in the same or similar way. In this study TWAP and rubber powder from truck tire treads are analyzed and compared with regard to their morphology, particle size distribution and composition. The particle size distribution of TWAP is broader than rubber powder containing also much smaller particles. The mineral content of TWAP is about 60%. These minerals can be residues of the pavement, brake wear but also rubber ingredients. In comparison to rubber powder, the impurities of TWAP are expected to have an impact with regard to potential applications and should be better separated.

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.

Detailed understanding of the carbon black–polymer interface in filled rubber composites

To characterize the nature of the interface between styrene-butadiene rubber (SBR) and carbon black (CB) in a filled rubber compound, we introduce an extraction protocol that uses toluene solvent in a high-pressure autoclave with sequential temperature steps of 90, 110, and 150 °C. This new approach removes unbound and physically bound (physisorbed) polymer from the CB-filled SBR compound to leave only chemically bound polymer which is 0.86% (0.0172 g polymer/g CB) and not zero as implied from extrapolating prior literature results. Rheological time sweeps on the unfilled gum SBR indicate that significant crosslinking can occur during annealing at 150 °C for this unsaturated polymer. This was the motivation for using the sequential extraction procedure versus direct extraction at 150 °C which gives a nearly six-fold higher amount of unextracted polymer due to such crosslinking. Analysis of the temperature dependence of bound rubber from 23 to 150 °C indicates that the physical interactions between the polymer and CB surface have a weaker component with a desorption energy (Ed) of 6.8 kJ/mol and a stronger component with Ed = 90.7 kJ/mol, the latter requiring an extraction temperature of 110 °C to remove the majority of it from the CB.

The Effect of Graphene Ultrasonic Coating on Recycled Rubber

Herein, the mechanical behavior of a graphene‐recycled rubber compound is investigated by performing static and dynamic tests. Water‐based graphene suspension is deposited on recycled rubber pads via an electrostatic addition process. Results on tensile and compression tests indicate a significant improvement of the compound in strength and in damping. They also indicate that the compound experiences significant elongation (up to 500%) as well as withstands high tensile forces, 300% greater than the force that the recycled rubber mix would withstand. The effective compression modulus of the compound is also shown to increase by about 3.2 times at 10% strain with respect to the one for the recycled rubber mix. Results suggest that the graphene‐recycled rubber compound can deliver a sustainable solution for vibration mitigation applications.

An experimental study on a novel reclaimed rubber compound for fiber-reinforced seismic isolators

Classical rubber seismic isolators reinforced with steel shims are generally large, heavy, and expensive so rarely used for housing buildings. In the last few years, different technologies have been investigated and fiber reinforced elastomeric isolators (FREIs) demonstrated to be a promising option. Only by properly combining a lower cost of raw materials including the manufacturing process and an easier installation process can result in a cost-effective solution. In the present study, novel reclaimed-rubber FREIs reinforced with low cost fabrics were designed and manufactured. A reclaimed compound (RC) has been developed resulting in mechanical properties not significantly different from virgin rubber. Mechanical characterization of the RC showed a typical response of soft compound even if with lower tensile deformation capacity. RC adhesion with polyester and nylon fabrics was investigated in order to prevent debonding between different layers. In this regard recycled-rubber FREIs with polyester and nylon fabrics were manufactured and tested in unbonded configuration. The devices showed promising performance and paved the way for the development of low-cost and environmental-friendly seismic isolators for housing buildings.

Online characterization of ambient temperature influence on die swell behavior of rubber compound

In this study, the influence of the ambient temperature in the range of 20–60 °C on the die swell behavior of rubber compound were studied by a capillary rheometer with new designed external heating device. The results demonstrated that the die swell ratio (B) increased rapidly in the initial phase and reached a stable value after a certain time. The time dependence of B was then calculated based on the experimental data using Burger's model. In addition, it can be found that B was proportional to the ambient temperature of the extrudate, since the relaxation time decreased obviously with increasing ambient temperature. At the constant time of 130 min, B in the range of 20–60 °C were 1.393, 1.405, 1.420, 1.425 and 1.438 mm, respectively. Furthermore, an equation was established to describe the relationship among the B, test time and ambient temperature. The calculated value was consistent with experimental data, which was 1.447 and 1.449 mm, respectively. While the equation was not applicable when the ambient temperature lay above 70 °C due to the decreased interaction between rubber and carbon black. It was also found that the contraction effect played a significant role on the behavior of die swell. B of the extrudate under 60 °C and 70 °C was reduced by 1.5% and 1.2%, respectively.

Constructing a fine dispersion and chemical interface based on an electrostatic self-assembly and aqueous phase compound in GO/SiO2/SBR composites to achieve high-wear resistance in eco-friendly green tires

The hazard to the ecosystem caused by rubber microparticles generated from tire abrasion has been a constant concern. Therefore, to protect this ecosystem, the development of a tire tread with high abrasion resistance is especially significant. Herein, γ-aminopropyltriethoxysilane (APTES) was used to modify graphene oxide (GO) and silica (SiO2) to obtain GO and SiO2 with positive charges (NG and NS). Furthermore, NG and NS were electrostatically self-assembled by using maleic anhydride (MAH) hydrolysis, thereby obtaining composite particles (NG-NS) with “bridged structures”. Also, the NG-NS/styrene butadiene rubber (SBR) compounds possessing fine dispersion of NG-NS were prepared by the aqueous compounding method. During the crosslinking process, the vinyl groups in NG-NS reacted with the vinyl groups of the SBR molecule chains, thus forming strong chemical interfacial interactions between the NG-NS and rubber macromolecules. Compared with an SiO2/SBR composite, the 300 % modulus, tensile strength, abrasion resistance of the NG-NS/SBR composite were improved by 125 %, 122 %, 83.3 %, respectively. Compared with a GO/SiO2/SBR composite, heat build-up in the NG-NS/SBR was decreased by 8.2 °C.

A comparison of machine learning methods to predict rheometric properties of rubber compounds

A comparison of machine learning methods to predict rheometric properties of rubber compounds

The use of modified "neodymium" polybutadiene in the formulation of the outer lining of conveyor belts

Currently, in the formulations of conveyor belts, polybutadiene rubber used with a content of up to 50 mass parts to improve the strength and wear resistance of rubbers. The results of a study of the properties of covering rubber compounds and rubbers based on a combination of polyisoprene, styrene-butadiene copolymer and polybutadiene used for the manufacture of conveyor belts were presented. The use of modified "neodymium" polybutadiene (SKD-ND-M), in the preparation of which a polyfunctional heterocyclic compound was used as a modifier, was proposed in the formulation of the lining of conveyor belts. This sample was characterized by an increased content of 1,4-cis units, a narrow MWD and a Mooney viscosity at the level of rubbers obtained without a modifier. We used serial brands of rubbers obtained on different catalytic systems: titanium (SKD) and neodymium (SKD-ND) as reference samples. A significant reduction in energy consumption in the manufacture of rubber compounds based on modified rubber in comparison with the rubber compound based on SKD was noted. It has been established that the use of SKD-ND-M instead of SKD made it possible to achieve an improvement in the technological properties of rubber compounds and their vulcanization characteristics, to ensure the required level of physical and mechanical properties of vulcanizates and performance indicators of lining rubbers. An improvement in the tear resistance of rubbers, as well as in compression set at 100°C and 125°C, when using modified "neodymium" polybutadiene in the lining rubber formulation instead of SKD rubber, was revealed. Replacing SKD-ND with a modified analogue provided a reduction in the abrasion rate of the conveyor belt lining, which will positively affect the increase in the service life of products based on it.

Classification of Hollow Rollers of Roller Machines for the Treatment of Polymeric Materials and Rubber Compounds (Survey of Patents)

Classification of Hollow Rollers of Roller Machines for the Treatment of Polymeric Materials and Rubber Compounds (Survey of Patents)

An Ogden-like formulation incorporating phase-field fracture in elastomers: from brittle to pseudo-ductile failures.

Over the past 50 years the Ogden model has been widely used in material modelling owing to its ability to match accurately the experimental data on elastomers at large strain, as well as its mathematical properties, such as polyconvexity. In this paper, these characteristics are exploited to formulate a finite-strain model that incorporates, through the phase-field approach recently proposed by Wu (Wu 2017 J. Mech. Phys. Solids 103, 72-99) for small strains, a cohesive damage mechanism which leads to the progressive degradation of the material stiffness and to failure under tension. By properly tailoring the constitutive parameters, the model is capable of encompassing a wide range of effects, from brittle to pseudo-ductile failure modes. A plane stress problem is formulated to test the model against experiments on double-network elastomers, which display a pseudo-ductile damage behaviour at large strain, and on conventional rubber compounds with brittle failure. The results show that the proposed model is applicable to fracture coalescence and propagation in a wide range of materials. This article is part of the theme issue 'The Ogden model of rubber mechanics: Fifty years of impact on nonlinear elasticity'.