Properties Of Rubber Compounds Research Articles

Influence of process parameters of a continuous final mixer on the properties of carbon black/rubber composites

Abstract As the final stage of the mixing process, the final mixing has a profound impact on the properties of rubber compounds. The influence of the process parameters of a continuous final mixer on the properties of carbon black/rubber composites is studied. It is found that there are two factors affecting the performance of the composite: the rotating speed of the dual rotors and the temperature of the continuous final mixer. When the temperature is unchanged, the extruding temperature of the final-mixing rubber compound increases with increasing rotating speed, and the Mooney viscosity, T10, T90 and rolling resistance gradually decrease. The Payne effect decreases first and then increases, and the overall trend gradually decreases. When the rotating speed is constant, as the temperature of the continuous final mixer rises, the extruding temperature also rises, and the temperature difference between feeding and extruding increases. Mooney viscosity and tensile strength increase. The Payne effect is more significant. T10, T90 and rolling resistance gradually decrease. The M300 of a vulcanized sample shows the following laws: When the control temperature is low, the influence of rotational speed is small, the fluctuation range is small, and has a steady rising trend; however, when the temperature is higher, M300 fluctuates greatly under the influence of rotational speed. The optimal process parameters of the rubber continuous final mixer are determined: the double rotor speed is 30RPM, and the temperature control temperature is 60–70 °C.

Correlations between lipid contents of natural rubber and tensile properties of natural rubber-based compound, using attenuated total reflection Fourier transform infrared spectroscopy

In this study, the lipid contents of different kinds of natural rubber were measured by attenuated total reflection–Fourier transform infrared spectroscopy. The correlation between these amounts were considered with the tensile properties of natural rubber compounds. The Pearson correlation coefficients were more than −0.9 for all cases, which confirms that the models are acceptable. These models were applied for the estimation of tensile properties in the case study. It was observed that the tensile strength, elongation at break, modulus 100%, and modulus 300% can be predicted by errors of about 4%, 17%, 18%, and 18% respectively. This is a simple, fast, and nondestructive way to estimate the tensile properties before the compound preparation.

Calcium-Lignosulfonate-Filled Rubber Compounds Based on NBR with Enhanced Physical-Mechanical Characteristics.

Calcium lignosulfonate in the amount 30 phr was incorporated into rubber compounds based on pure NBR and an NBR carbon black batch, in which the content of carbon black was 25 phr. Glycerine, as a cheap and environmentally friendly plasticizer, was applied into both types of rubber formulations in a concentration scale ranging from 5 to 20 phr. For the cross-linking of rubber compounds, a sulfur-based curing system was used. The work was aimed at the investigation of glycerine content on the curing process and rheological properties of rubber compounds, cross-link density, morphology and physical-mechanical properties of vulcanizates. The results show that glycerine influences the shapes of curing isotherms and results in a significant decrease between the maximum and minimum torque. This points to the strong plasticizing effect of glycerine on rubber compounds, which was also confirmed from rheological measurements. The application of glycerine resulted in better homogeneity of the rubber compounds and in the better dispersion and distribution of lignosulfonate within the rubber matrix, which was subsequently reflected in the significant improvement of tensile characteristics of vulcanizates. A higher cross-link density as well as better physical-mechanical properties were exhibited by the vulcanizates based on the carbon black batch due to the presence of a reinforcing filler.

Enhancement of the properties of carbon-black-filled natural rubber compounds containing soybean oil cured with peroxide through the addition of coagents

Due to the hazard of the commercial rubber processing oil such as distillate aromatic extract (DAE), many rubber researchers play attention to find the green alternatives. Vegetable oils seem to gain a lot of attraction for this. It is not just only due to their environmentally friendly nature but also their abundance and affordable cost. The use of soybean oil (SBO) for the carbon black-filled rubber compounds was focused here and comparatively discussed with the use of DAE. Furthermore, this work also proposed the way to improve the mechanical properties and environmental endurance of the rubber compounds containing SBO by adding coagents. There were two types of coagent including trimethylolpropane trimethacrylate (TMPTMA) and triallyl isocyanurate (TAIC) used here. It was found that the cure time, cure rate index, and cure reaction rate constant of SBO-added rubber compounds with and without coagents were higher than those of DAE-added rubber compounds, whereas the activation energy of SBO-added rubber compounds was lower than the one with DAE. Without coagent, the mechanical properties of rubber compounds with DAE and SBO are equal. However, the addition of coagents improved the mechanical properties of rubber compounds containing SBO. The modulus at 100% strain, modulus at 200% strain, and tensile strength of TMPTMA-added rubber compounds increased by 41%, 48%, and 15%, respectively, whereas the rubber compounds with TAIC increased by 7%, 8%, and 20%, respectively, when compared to the one with SBO alone. Interesting, the SBO-added rubber compounds with and without coagents showed better thermal aging and ozone resistances than the DAE-added rubber compounds. All results showed that the presence of coagents especially TMPTMA gave the SBO-added rubber compound with the superior performance to the DAE-added rubber compound and the SBO-added rubber compound without coagent.

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.

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.

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.

Verification of the probability of elastomers degradation in natural environments

Abstract A wide range of elastomers allows to manufacture products that meet high demands of consumers. They are prepared from a mixture of several rubbers, rubber chemicals, additives and reinforcing materials (fibres), which allows you to obtain the desired properties of the products. The other components of rubber compounds are fillers, carbon blacks and plasticizers. Rubber chemicals supplement the mixture in small quantities of related products, which affect vulcanization and regulate their properties, so they have an irreplaceable role in the preparation of rubber products. The aim of experimental part is to assess the properties of the degradation environment on samples of rubber composites to change their properties. The result of the performed mechanical tests to evaluate and compare the obtained values of mechanical properties of rubber compounds and to predict the possibility of biological degradation of the tested material.

Influence of Mixed Sulfur and Peroxide Curing Systems on Cross‐Linking and Properties of Rubber Compounds Based on EPDM

AbstractIn this work, sulfur vulcanization system, peroxide vulcanization system, and combined sulfur and peroxide curing systems are applied for cross‐linking of rubber compounds based on ethylene propylene diene monomer rubber. The goal is to investigate the influence of curing system composition on cross‐linking and properties of rubber formulations. The combination of both vulcanization systems in cross‐linking of rubbers combines the pattern of carbon–carbon linkages and sulfidic bridges, which gives the real presumption to modify physical–mechanical properties of final vulcanizates. The results reveal that the combination of vulcanization systems affects the curing characteristics, cross‐link density as well as physical–mechanical properties of tested materials. In comparison with vulcanizates cured only with sulfur or peroxide system, rubber compounds cross‐linked with mixed sulfur and peroxide curing systems exhibite higher tensile strength and elongation at break.

Monitoring of shear heating effects during injection molding of rubber to improve the process control

This work aims to get new insights into the “process monitoring tool” proposed by the authors for the online monitoring of the shear heating phenomenon during injection molding of technical rubber parts. The online monitoring is based on direct measurement of the surface rubber temperature (shear heating temperature, TSH) by an infrared thermal camera of the rubber as it leaves the extruder barrel of the injection molding machine. The measured rubber temperature is a process indicator giving the thermal history of the rubber compound injection and process safety. Therefore, this fast process control is applied to industrial applications to investigate the processing behavior of ethylene acrylate (AEM) rubber compounds. In particular, the relationships between TSH vs injection pressure, vs injection speed, vs screw speed rotation and vs screw length over diameter ratio (L/D ratio) and vs AEM rubber compound properties variation due to exceeding the shelf life are investigated. The results show that TSH is manly influenced by the screw L/D ratio, followed by injection pressure and screw speed rotation (especially if are set to higher levels), whereas the injection speed is the least effective parameter to reduce TSH. Furthermore, a previously found robust correlation between the shear heating parameter (ηSH) and the minimum torque measured in rheometric laboratory tests (ML) is used to show the noteworthy deviation from the proportional trend when the AEM rubber compound exceeded it shelf life. Therefore, the coefficient of determination of {text{log}}eta_{{{text{SH}}}} vs ML curves provides a good indication of process stability, while it is running.

The link between swelling ratios and physical properties of EPDM rubber compound having different oil amounts

This new observation demonstrated that an increase in oil amounts within ethylene propylene diene monomer (EPDM) compounds decreased the crosslink density and the storage modulus but increase the elongation at break after tensile testing. The compounds with high oil amounts were observed to release oil particles when dissolved in toluene solutions and that increased their swell ratios. Consequently, the crosslink density had a perfect negative linear correlation with the elongation at break and a strong power-law correlation with the swell ratios. This work guides the material chemists and engineers during compound formulations when an increase in oil amounts is required.

Design of self-healing styrene-butadiene rubber compounds with ground tire rubber-based reinforcing additives by means of DoE methodology

In the effort to find a balance between the mechanical properties of self-healing styrene-butadiene rubber (SBR) compounds, before and after a macroscopic damage, a study based on the use of devulcanised tire residue (dGTR) as reinforcement has been carried out. Two full factorial designs and their analysis of variance (ANOVA) were used to overcome the challenge of relating the multiple microstructural variables of dGTR to the mechanical properties of the compounds in pristine and healed states. The design of experiments (DoE) predict that the use of dGTR-based reinforcements, with a decrease in network density higher than 50%, enables the incorporation of more than 40 phr of reinforcing filler, increasing the tensile strength in the pristine state (more than 4 times) and mitigating its negative effect on the healing process. Experimental tests have validated these theoretical predictions. This research demonstrates that it is not necessary to control the selectivity of the devulcanisation process. Therefore, it has been demonstrated that only by increasing the dGTR surface network density breakage it is possible to incorporate significant amounts of the residue from simple recycling processes in order to improve the performance of high value-added rubber formulations, such as self-healing materials.

Unfilled Natural Rubber Compounds Containing Bio-Oil Cured with Different Curing Systems: A Comparative Study

This study focuses on the properties of unfilled natural rubber compounds containing bio-oils cured with a peroxide curing system and then discusses the comparisons to those cured using the sulfur system from our previous work. Two types of bio-oils, i.e., palm oil and soybean oil, were used, and distillate aromatic extract (DAE)-based petroleum oil was employed as a reference. The bio-oils caused no significant change in the vulcanization of rubber compounds cured using peroxide. However, the compounds containing bio-oils and cured with sulfur showed a faster vulcanization than the ones with DAE. The bio-oils strongly affected the crosslink density of rubber compounds in both curing systems. The use of bio-oils caused a low crosslink density due to the possible implication of curing agents to bio-oil molecules. The properties of rubber compounds dependent on the different levels of crosslink density were also investigated. The results revealed that when the crosslink density increased, the modulus, tensile strength, and hardness of the rubber compounds increased and the elongation at break and compression set decreased. The use of bio-oils in the rubber compounds cured with different curing systems gave low modulus at 300% strain, tensile strength, and hardness but high elongation at break and compression set when compared to the ones with DAE. However, no significant change was observed for the compression set of the rubber compounds cured using sulfur. With the presence of bio-oils, the properties of rubber compounds cured with sulfur system deteriorated less than those of the ones cured with peroxide.

Room temperature Self-healable and extremely stretchable elastomer with improved mechanical Properties: Exploring a simplistic Metal-Ligand interaction

The dynamic supramolecular crosslinking reactions like imine bond formation, disulfide metathesis reactions, Diels Alder reactions, metal–ligand interactions, H-bonding, and ionic interactions are broadly used for the self-healing application of elastomers. Herein, we have developed a new self-healable and extremely stretchable elastomer based on robustness and dynamic metal–ligand coordination bonds between the API ligand and the Zn2+ metal ion moieties incorporated onto the XNBR rubber backbone. The FT-IR analysis confirmed the formation of amide linkage and metal–ligand coordination bonds into the XNBR rubber backbone. The healing performance and mechanical properties of various rubber compounds depend on the dosages of metal ions and the type of crosslinking systems. The metal–ligand crosslink compounds exhibit excellent healing performance over the sulfur crosslinking system. Differential scanning calorimetry, rubber process analyzer, crosslinking density, and morphology studies are indicated to characterize the metal–ligand interactions in the XNBR rubber matrix. The metal–ligand cross-linked XNBR rubber with 3 parts of Zn2+ metal ion demonstrates an excellent healing performance of 91.2%, with the tensile strength of 5.7 ± 0.8 MPa at room temperature for 24 h is much higher than the covalently cross-linked elastomers. The metal–ligand coordination bonds are entirely dynamic and thermoreversible during the rebuilding process and obtain an excellent self-healing property than the sulfur curing system.

Sepiolite-Based Anisotropic Nanoparticles: A New Player in the Rubber Reinforcement Technology for Tire Application

Elastomer reinforcement with nanofillers has been a main rubber technology topic since the discovery of rubber vulcanization. Starting from carbon black, many researchers studied the correlations between the reinforcement of rubber and the colloidal properties of the reinforcing filler. The advent of silica allowed the experimentation of a playground of chemistries at the filler-rubber interface. In the increasing complexity of nowadays car manufacturer requests, reinforcing fillers play a pivotal role in determining the set of properties, which make a specific compound suitable for its applications. This effort of continuous improvement of rubber compound properties is pushing the tire industry towards novel solutions, and the silica/CB filler reinforcing technology will likely soon accept at least a third reinforcing filler as a major constituent of rubber compounds. While all major tire manufacturers build continuous knowledge on candidates such as carbon allotropes and 2-D nanoclays, Pirelli is paving the way for Sepiolite-derived nanofillers. Being Sepiolite naturally sourced, safe, and chemically playful, this unique 1-D phyllosilicate bears the promise of changing the game of elastomer nano-reinforcement, with the optional characteristic of giving mechanical anisotropy to the rubber compound. In this review, the historical progress on rubber reinforcement with sepiolite will be summarized, with an example of application in a commercially available Pirelli product, progenitor of the Smart-Net Silica® technology.

Study of non-negligible chemical reduction of ZnO in the rubber industry

Although the presence of small portion of zinc in the tire industry has been employed as activator, it should be concerned as the non-negligible chemical toxics and risks. The aim of this work was to study the effect of zinc oxide (ZnO) on physical and mechanical properties of tire rubber compound. The control characteristics of the composites were determined by the composites of practical compounds and vulcanizates by filling of sulfur and curing of a hot press machine. The properties of the composites, i.e. Mooney viscosity, curing time, tension, etc, were characterized. Generally, ZnO could work coupled with stearic acid (SA), the experimental was prepared by reducing ZnO at 20% and reducing stearic acid at approximately ratio to prevent excessive amount. The comparative data revealed the trend of the changes in the physical and mechanical properties just not lower at the same percentage. This recognized study supports the high possibilities in enhancing low ZnO and stearic acid content typical.

Finite Element Analysis of elastomer: Case study – Rolling resistances of pneumatic and solid tyres

EU tyre labelling rules have been applied since November 1st, 2012, to inform about the performances of tyres on fuel efficiency (rolling resistance), safety (braking on wet surfaces) and noise (external noise). The tyre labels help customers to make their purchase decisions by trade off on tyre performances and prices. Consequently, manufacturers have to engineer their products so that their tyres are classified on top of the label categories. Tyre rolling resistance involves in many kinds of tyre knowledge such as rubber formulations, tyre structures and tyre tread patterns. Generally, 70% of tyre rolling resistance depends on the hysteresis properties of rubber compounds and 30% depends on other properties such as road conditions, tyre pressures, load carrying, vehicle speeds, and tyre tread designs. From this point of view, even if rubber compounds are formulated to have good hysteresis properties, they can help reduce tyre rolling resistance up to 70%. If tyre rolling resistance needs to be further reduced, tread designs have to be considered. Therefore, this case study will show how to reduce tyre rolling resistance by using Finite Element Analysis (FEA). Pneumatic light truck tyres were used to study their tread patterns, tread depths and contact areas affecting their rolling resistances, while solid tyres were used to study on their tread patterns, tread depths, contact areas and tyre structures affecting their rolling resistances. The FEA results showed that tread patterns had high effects on rolling resistance of pneumatic light truck tyres while they had little effects on solid tyres. Contact areas and tread depths affected rolling resistances of both tyres. Increase in contact areas reduced tyre rolling resistances while increase in tread depths resulted in higher tyre rolling resistances.

Hybrid In Situ Reinforcement of EPDM Rubber Compounds Based on Phenolic Novolac Resin and Ionic Coagent

For the design of stretchable and flexible high-performing materials, the reinforcement of elastomeric grades plays a crucial role. State-of-the-art fillers such as carbon black benefit from a high reinforcement but often negatively affect the processing and mixing properties of rubber compounds. To overcome this drawback, the synergistic properties of hybrid in situ filler systems are studied for EPDM compounds comprising a phenol novolac resin and ionic coagents such as zinc (meth)acrylates (ZD(M)A. With the help of a combined novolac/ZD(M)A system, the compounds could be tailored in a unique way towards higher toughness and enhanced cross-link density. Further, the fracture surface of the EPDM–novolac compounds was analyzed by scanning electron microscopy, revealing a significant change of the morphology from rough and disordered to smooth and homogenous for samples with coagents. In addition, the results clearly showed that the introduction of ionic coagents is able to compensate shares of carbon black filler in the EPDM compound. The toughening of samples with zinc (meth)acrylates is attributed to the synergistic formation of an interpenetrating polymer-filler network by simultaneous covalent and ionic cross-linking.

The rheological and mechanical properties of natural rubber/graphene composites

This research focuses on the use of graphene as a filler for natural rubber (NR). The purpose of using graphene is to improve the mechanical properties of rubber compounds and their processing characteristics. Graphene (G) consists of carbon atoms and is an essential filler for polymers to enhance electrical and mechanical properties. The addition of graphene to rubber can improve the wear resistance and mechanical strength of rubber products. Thus, the effect of the graphene filler composition is interesting to study. Variety of graphene loads (10, 20, and 30 part hundred rubber (phr)) were combined with a variety of sulfur fillers (S) (10 and 20 phr) and then composited with natural rubber. The effect of variations in a load of graphene and sulfur fillers on the rheological properties, abrasion resistance, and compression set were studied. The results showed that the optimal combination of the G/S load variation was 20/10 phr. It leads to a more extraordinary strengthening ability that is binding rubber molecules so that the interactions occurred, both physical and chemical, could be formed better with the NR molecular chain. This resulted in distinct rheological properties enhancement such as torque modulus and curing time. In contrast, the mechanical properties like abrasion resistance and compression set were still good. The FTIR Spectra of natural rubber-graphene composites confirmed that good filler disperses were obtained due to several intramolecular interactions of carbon graphene with NR molecules. Graphene can be used as a filler for rubber products, mainly rubber, abrasion, and compression resistant, and an alternative for commercial fillers.