Mechanical Properties Of Rubber Research Articles

Revealing the Effect of the Length of Chains on Rubber Mechanical Properties by the Two‐Component Quantum Mechanical Gaussian Model

AbstractThe special mechanical properties of natural rubber originate from the stretching of the network chains (i.e., cis‐1,4‐polyisoprene chains) in the rubber network. The chains with various lengths exhibit various relative extensions, leading to various normalized energy contributions to the mechanical properties of rubber. However, the stretching behaviors of cis‐1,4‐polyisoprene chains with different lengths are not studied clearly. Here, the stretching behavior, which is the basis for analyzing the normalized energy contribution, is obtained by the modified freely jointed chain model. Next, using a new statistical model, i.e., the two‐component quantum‐mechanics Gaussian (TCQMG) model, the relative extension–length relationship of network chains is determined. Combining the above results, the energy contributions of network chains with different lengths are analyzed. The results show that long and short chains show different stretching states. The following can be explained by these results: short chains play an important role in the mechanical properties of rubber. As the network chain density increases, the average length of the chains decreases, leading to the variation of the normalized extensions. It is found that the variation of the normalized extensions is responsible for both the effects of the network chain density and network chain length on the mechanical properties of rubber.

Ageing Behavior of Rubber Compounds Prepared with Different ZnO Types

Zinc oxide is considered as the most widely used activator that influences curing reaction kinetics and promotes short sulphide crosslinks to achieve higher crosslink density in rubber compounds. Besides its effect on curing process, it has beneficial effects on the physical and mechanical properties of rubber as well. However, its level should be minimized in rubber compounds because of its toxicity for human health and environment, especially on aquatic wildlife. One of the potential routes for decreasing ZnO level is to use composite ZnO materials where ZnO particles are coated. In this study, composite ZnO materials having ZnO:CaCO3 ratio as 40:60, 60:40 and 90:10 are used in SBR/BR compounds and their effects on mechanical properties under ageing conditions are investigated and compared with the conventional white seal ZnO and active ZnO types. The findings have shown that all composite materials have no negative effect on mechanical properties under ageing conditions, thus they can be used as alternative materials to conventional activators.

Recycling of landfill waste tyre in construction materials: Durability of concrete made with chipped rubber

The goal of current research is to study the effect of waste tyre as a replacement for coarse aggregate at high levels in concrete for non-structural applications to address one of the serious environmental concerns. To reach this aim, waste rubber in a size range of 10–15 mm which needs less energy and cost for grinding compared to fine rubber was used. The total volume of coarse aggregate was substituted by rubber at the rates of 25%, 50%, 60%, 70% and 80%. Mechanical properties were studied through compressive and flexural strength and hardened density tests. Moreover, durability was comprehensively investigated via water absorption, drying shrinkage, electrical resistivity, chloride migration, carbonation resistance and resistance against acid attack tests. Sound absorption performance of different mixes at low and high frequencies were also compared to monitor the impact of rubber content. The results indicated that by the addition of rubber mechanical properties reduced, nevertheless, durability improved. Using rubber enhances the concrete ductility and reduces the density making it appropriate for lightweight concrete. The chloride migration coefficient was reduced up to 80% and electrical resistivity increased up to 87%, by using 80% rubber. Besides, rubberised concrete developed in this research demonstrated superior functional advantages over plain concrete in terms of acoustic performance and sustainability. Despite having lower strength by using rubber in concrete, rubberised concrete made with high content of cost-effective coarse rubber particle is appropriate for non-structural usages particularly in regions where either possibility of aggressive environment is a concern or noise attenuation is critical.

Hybrid viscoelastic damper using natural rubber compound, waste of rubber tire crumb with various compacted sands (iron sand, natural sand, and silica sand) to increase damping property for non-engineered buildings

To reduce lateral deformation due to earthquake shake has been carried out by strengthening techniques. Such techniques require additional structural elements such as bracing or shear wall, if not applying additional new materials on beams or columns such as CFRP. This study focuses on the formation of the hybrid rubber dampers from materials such as natural rubber compound (NRC), waste of rubber tire crumb (WRTC), compacted natural sand, iron sand, and silica sand. The main goal of this research is to investigate the dynamic properties of hybrid materials of compacted various sands encapsuled with the NRC and WRTC compound. Nonetheless, the mechanical properties of rubber, such as tensile strength and modulus of elasticity, were also tested. In this research, the specimens were in the form of a square block of 100 x 100 mm2 base and 25 mm thickness and consisted of two types of specimens for reference i.e., fully natural rubber compound (NRC) and blended NRC with 25% by volume of the WRTC, namely MRTC. Furthermore, other three types of hybrid viscoelastic dampers (HVD) were also provided i.e., 1) compacted natural sand, 2) compacted iron sand, and 3) compacted silica sand, which were all wrapped with WRTC in a proportion of 3:4 by volume. The results show that the addition of the MRTC reduces the tensile strength and elastic modulus in comparison to the NRC but increases the damping properties. Moreover, the elaboration of compacted natural sand, iron sand, and silica sand in the HVD also shows an increase in the damping properties up to 200%.

Optical Characteristics of Stretchable Chiral Liquid Crystal Elastomer under Multiaxial Stretching

AbstractChiral liquid crystal elastomers (CLCEs) are soft photonic materials that exhibit both the photonic characteristics of nanoscale periodic helical structures and mechanical properties of rubber. Owing to its elasticity, the structural color of CLCEs can be tuned through mechanical deformations known as mechanochromism. Thus far, there is significant research attention to exploring the mechanochromism of CLCEs. However, most studies have only discussed the color shifting of CLCEs under uniaxial deformation. Therefore, the optical and chiral structural deformation behaviors of CLCEs under multiaxial stress are not well understood. This study investigates multiaxial (uniaxial, biaxial, and out‐of‐plane) stretching‐induced helical structure change and the resulting optical properties of CLCEs. The results confirm that uniaxial stretching leads to a loss of intrinsic circular polarization selectivity in CLCEs due to helix unwinding deformations, while biaxial and out‐of‐plane stretching maintain circular polarization.

Novel perspectives on self-monitoring internal rubber failure using piezoresistivity

Carbon black (CB) fillers are often used to increase the ultimate strength and durability of rubber products. Incidentally, CBs are also electrically conductive and this property at low filler concentrations was successfully exploited by several researchers to monitor changes in mechanical properties of rubber by piezoresistance evaluation.In the present work, piezoresistive response of deformed natural rubber (NR) filled with higher concentrations of CB, which are often encountered in rubber products under dynamic loading conditions like tires, conveyor belts, vibration dampers and the like was investigated. Unfortunately, high carbon black content significantly decreased piezoresistive signal, severely limiting the self-monitoring capability. Moreover, unexpectedly high and undesirable for electromechanical application such as precursor of shoulder peak phenomenon (PSPP) and shoulder peak phenomenon (SPP) were observed.However, these otherwise undesirable phenomena in a noble way was used for self-monitoring the rubber integrity during cyclic deformation. The gradual increase in residual strain, indicating rubber matrix fatigue, was clearly related to changes in experimentally detectable electrical resistance as a function of PSPP and SPP.The study is optimistic of a new concept for self-monitoring and forecasting rubber structure degradation under long-term cyclic loading predictable from simple obtainable piezoresistive response.

Prediction of the optimal vulcanization of a fiber‐reinforced elastomeric isolator made of natural rubber‐ethylene propylene diene monomer blend

AbstractTo seismically isolate a structure, it is possible to interpose a rubber device between the foundation and superstructure that increases the period of the superstructure, a feature that allows the structure to be “transparent” to the seismic excitation. A package of several rubber pads typically constitutes a seismic isolator; they are 10–20 mm thick vertically interspersed with either steel laminas or fiber‐reinforced polymer dry textiles suitably treated. So, the rubber has a primary role and must be vulcanized correctly to create the polymer cross‐linking properly. All rubber mechanical properties are strongly affected by curing temperature and curing time. Under vulcanization is a typical production error that suppliers make in large‐scale productions, especially when the size of the devices is considerable. It is common to deal with elastomeric isolators where rubber pads have been treated at a largely suboptimal temperature. This article proposes a numerical model for predicting the cross‐linking degree of rubber pads used in seismic isolation and made by a natural rubber‐ethylene propylene diene monomer rubber compound. The aim is to correctly define the optimal curing temperature and exposition time for producing a rubber quadruple shear test specimen and a fiber reinforced elastomeric isolator (FREI). The model is a kinetic one and takes into consideration the induction time. An experimental investigation has been conducted to validate the model with visible inspections and hardness measurements taken on the rubber pads (quadruple shear specimens) and the rubber devices. The results have shown the reliability of the new numerical model proposed, with a homogeneous mechanical properties distribution obtained within the rubber pads and the FREI.

Biobased epoxidized natural rubber/sodium carboxymethyl cellulose composites with enhanced strength and healing ability

Conventional vulcanized rubbers cause a non-negligible waste of resources due to the formation of 3D irreversible covalently cross-linked networks. The introduction of reversible covalent bonds, such as reversible disulfide bonds, into the rubber network, is an available solution to the above problem. However, the mechanical properties of rubber with only reversible disulfide bonds cannot meet most practical applications. In this paper, a strengthened bio-based epoxidized natural rubber (ENR) composite reinforced by sodium carboxymethyl cellulose (SCMC) was prepared. SCMC forms a mass of hydrogen bonds between its hydroxyl groups and the hydrophilic groups of ENR chain, which gives the ENR/2,2′-Dithiodibenzoic acid (DTSA)/SCMC composites an enhanced mechanical performance. With 20 phr SCMC, the tensile strength of the composite increases from 3.0 to 10.4 MPa, which is almost 3.5 times that of the ENR/DTSA composite without SCMC. Simultaneously, DTSA covalently cross-linked ENR with the introduction of reversible disulfide bonds, which enables the cross-linked network to rearrange its topology at low temperatures and thus endows the ENR/DTSA/SCMC composites with healing properties. The ENR/DTSA/SCMC-10 composite has a considerable healing efficiency of about 96 % after healing at 80 °C for 12 h.

Significant Influence of Bound Rubber Thickness on the Rubber Reinforcement Effect.

In this work, the contribution of different types of carbon blacks (N115, N330, N550, N660) and their primary and secondary thermally cracked recovered carbon blacks to the mechanical properties of NR composites was evaluated. The thermally cracked recovered carbon blacks were prepared by cracking the rubber composites at 500 °C and de-hybridizing them at 900 °C. The characterization of the thermally cracked recovered carbon blacks by scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy showed that carbon blacks after primary and secondary thermal cracking recovery were more prone to aggregation and exhibited a higher degree of carbon defects. The number and type of functional groups on the surface of these carbon blacks were significantly reduced. For NR composites with pristine samples added, the mechanical properties and the bound rubber content tests showed that the mechanical properties of the NR composites became weaker with the increase in carbon black particle size. The bound rubber content also decreased with increased carbon black particle size. The mechanical properties of the NR composites reinforced with carbon black recovered by primary and secondary thermal cracking would therefore decrease. The results of AFM and DSC tests further confirmed the decreasing trend of bound rubber. The present work demonstrates the effect of bound rubber content variation on the mechanical properties of rubber, demonstrates the morphology of bound rubber more visually, and provides new insights into the reinforcement theory of CB.

The effect of temperature and vulcanisation time on the thermal and mechanical properties of rubber used in tires

ABSTRACT The thermal and mechanical properties of rubber used in tires were measured experimentally. The effect of temperature on the thermal properties and the effect of vulcanisation time on the mechanical properties are analyzed. The specific heat capacity and thermal conductivity both increase with increasing temperature, and the specific heat capacity and thermal conductivity are approximated as linear functions of temperature. The tensile strength, elongation at break and abrasion properties of vulcanizate are significantly affected by the vulcanisation time. As the vulcanisation time increases, the tensile strength first increases and then decreases, and the elongation at break changes with the vulcanisation time on the contrary. The wear volume of tread rubber first decreases and then increases with the increase of vulcanisation time. At the positive vulcanisation time, the tensile strength of the vulcanizate reached the maximum value, while the elongation at break and wear volume reached the minimum value.

Characterization of Natural Rubber, Styrene Butadiene Rubber, and Nitrile Butadiene Rubber Monomer Blend Composites Loaded with Zinc Stearate to Be Used in the Solid Tire Industry

Vulcanization is an important step in the manufacture of solid tires in which the crosslinking process occurs. In vulcanization, the materials commonly used as activators and coactivators are ZnO and stearic acid, respectively. In this research, ZnO and stearic acid were replaced with zinc stearate to improve the characteristics of vulcanized rubber. Zinc stearate was applied in four formulas with a composition of 5 to 9 phr. A formula that is often used in the rubber industry was used as a comparison, and ZnO and stearic acid of 5 phr and 2.5 phr, respectively, were applied. The rubber compound for solid tire production was developed using an open mill at a compounding temperature of 45 °C ± 5 °C. The vulcanization process of developing the rubber compound into vulcanized rubber was carried out at 150 °C for 20 min. Rubber compound test results showed that the use of zinc stearate at a ratio of 8 phr accelerated the curing time (t90) between 58.3% and 69%, the scorch time (ts2) between 22.4% and 95.5%, and the torque delta (Δs) between 17.67 and 24.21 kg-cm. In addition, the vulcanized rubber mechanical properties test results for the compression set parameter increased between 28.6% and 57.1%. Scan results with SEM–EDS showed that using ZS could improve the homogeneous distribution of the material in the vulcanized matrix of solid tire rubber.

Numerical and experimental analysis of free vibrations and static bending of a sandwich beam with a hyperelastic core

In the present paper, the hyperelastic behavior of a sandwich beam and isotropic beam is numerically and experimentally analyzed. To this end, the sandwich beam has a natural rubber-made core, and metal skin is made of aluminum; the isotropic beam is built of natural rubber. Free vibrations and quasi-static bending are investigated for both sandwich and homogeneous beams. Also, an axial tensile test is conducted based on ASTM D412 standard to obtain the natural rubber's mechanical properties. In the experimental bending test, the displacement and strain contour are extracted by the Digital image correlation method.

Study of the influence of temperature-time conditions of vulcanization on the properties of elastomer compositions

The article was devoted to the study of the influence of temperature-time conditions of vulcanization on the kinetic parameters of structuring of rubber compounds and the physical and mechanical properties of rubbers. The object of the study was an elastomeric composition based on natural rubber and containing a sulfur curing system. The investigated rubbers were obtained under various time conditions and temperatures of 143, 160 and 170°C. It was determined that with an increase in the vulcanization temperature, the values ​​of the minimum torque decrease by 11.6–15.6%, and the maximum torque increase by 3.5–4.1%, at the same time the density of rubber cross-linking increases by 6.2– 7.5%. Analysis of the results of determining the physical and mechanical parameters of rubbers revealed that at a temperature of 143°C the vulcanization time does not significantly affect the elastic-strength parameters of rubbers and vulcanizates are characterized by the highest values of tensile strength both before and after thermal aging. It has been established that with an increase in the vulcanization temperature, side processes are activated, leading to a decrease in the elastic-strength properties of rubber (a decrease in tensile strength by 9.2–16.4% and elongation at break up to 7.2%). Vulcanizates obtained at 170°C are characterized by the lowest indicators of elastic-strength properties, hardness Shore A and rebound resilience, which is due to the density of the network and the nature of cross-links. The research results showed that when choosing the final vulcanization mode, especially for multilayer products, it is necessary to take into account not only the energy consumption in the production of finished products, but also the influence of temperature and time parameters on the complex of physical and mechanical properties of each component of the product.

BREAK OF A CABLE OF A CABLE ROPE

Establishing the influence of changes in time properties of rubber on the stress state of the rubber-traction body with a damaged cable. The method of research consists in the analytical solution of the model of the humorous traction body taking into account the rupture of the continuity of the cable and the change in the properties of the rubber. The dependences of the change of the stress state of the traction body of the humotross with the broken structure due to the rheology of the rubber shell are established. An algorithm for determining the stress state of a rubber traction body in case of a broken one is formulated. Structure and manifestations of rubber shell rheology. It is shown that the loads on the cables caused by the discontinuity of one of them lead to a local redistribution of forces almost only between two cables - damaged and adjacent; in case of damage non-extreme cable forces change almost only in three cables - damaged and two related to it. At the same time there are no extreme values ​​of internal efforts of loading of cables depend on the change in the shear modulus of the rubber material over time. Significant rubber shifts were detected occur between the damaged rope and adjacent to the length of the rope; shear angles the rubber between other cables is much smaller relative to the displacements in the local redistribution zone forces and stresses and change slightly due to the aging of the rubber over time. The mechanism of influence of changes of properties of rubber on pressure is established the condition of the traction body, taking into account the rupture of the continuity of the cable and changes in the properties of the rubber. Taking into account the dependence of the stress-strain state of the rope with local violations of the cable base from changes in the mechanical properties of rubber provides the ability to predict the stress state of the rope to improve safety and reliability the use of rubber traction bodies that have a significant service life. Further research should focus on the development of a method of continuous automatic control of rope damage in the rope.

The effect of woven oil palm empty fruit bunches (OPEFB) filler fiber on the mechanical properties of natural and synthetic rubber

Oil palm empty fruit bunches (OPEFB) are biomass from palm oil (CPO) processing which can be produced into long lignocellulose and made of yarn as raw material for woven textiles for sandwich biocomposite applications. The purpose of this study was to obtain a biocomposite sandwich variation of natural rubber, butyl, and silicone reinforced with OPEFB woven fibers at optimum filler concentration by studying mechanical properties. The biocomposite of rubber sandwiches with OPEFB fiber reinforced with concentrations of 14, 20, and 28 sheets with a size of 10 x 10 x 1 cm. The methodology used was layered printing with constant pressure and heat using a hot press. The best fiber concentration based on mechanical properties was a composite with a fiber concentration of 28 sheets on 70 shore A hardness natural rubber. This was because the fibers in the composite functioned as load bearers, where this containment was carried out by the distribution of stress. The more fiber concentration, the more effective and uniform distribution of stresses will be, so that an increase in the mechanical properties of the composite occurs. The mechanical properties of rubber have been shown to increase with the addition of fiber as a reinforcing material, the ratio of the impact strength of rubber (control) and fiber-reinforced rubber was lower than that of fiber-reinforced rubber. The natural rubber had an impact strength of 48 kJ/m2, while natural rubber with fiber reinforcement had a higher impact strength value of 321.40 kJ/m2.

Influence of various factors on surface properties of elastomeric materials based on nitrile butadiene rubbers

Objectives. The influence of the technological additive content and accelerated aging conditions on the surface energy and elastic-strength properties of nitrile butadiene rubbers with an average acrylic acid nitrile content and rubbers based on them were studied in the paper.Methods. The free surface energy of the samples was determined under the standard conditions and in the accelerated aging conditions with the use of the Owens, Wendt, Rabel, and Kaelble method.Results. It was shown that the elastomeric materials surface energy is influenced by surfactants such as rosin and stearic acid, which are typical ingredients of rubber compounds. It was also found that the thermal aging effect on the physical and mechanical properties of rubbers based on nitrile butadiene rubbers depends on the method of rubber isolation from latex and on the nature of the surfactant components in the samples.Conclusions. The analysis of the results obtained shows that the change in the vulcanizates physical and mechanical properties, depending on the technological additive content and the temperature effect, occurs along with a change in the critical surface tension.

Investigation of a static rope with a cable break

Abstract. Establishing the influence of changes in the temporary properties of rubber on the stress state of the rubber traction body with a damaged cable. The method of research consists in the analytical solution of the model of the humorous traction body taking into account the rupture of the cable continuity and the change in the properties of the rubber. The dependences of the change of the stress state of the traction body of the humotross with the broken structure due to the rheology of the rubber shell are established. An algorithm for determining the stress state of a rubber traction body in case of its failure is formulated. It is shown that the loads on the ropes caused by the rupture of one of them lead to a local redistribution of forces almost only between two cables - damaged and adjacent; when damaged, non-extreme cable forces change in almost only three cables - damaged and two related. There are no extreme values of the internal load forces of the cables, which depend on the change of the shear modulus of the rubber material over time.
 Construction of a method for determining the influence of impulses of individual cables of a cable rubber rope on its stress state.
 Development and solution of the model of stress-strain state of the cable rubber rope with breaks in the continuity of the cables.
 Methods of determining the stress state of a cable rope with a damaged cable.
 The mechanism and nature of the influence of the impulses of the continuity of the cable of the cable rubber rope on its stress-strain state.
 The developed method allows to take into account the influence of cable bursts on the stress state of the humorous cable rope of arbitrary design. Its application will allow to reasonably determine the minimum reserves of strength under the condition of safe use of the rubber rope, including in case of rupture of individual cables.
 The mechanism of influence of change of properties of rubber on pressure is established by a condition of a traction body taking into account a rupture of continuity of a cable and change of properties of rubber. Taking into account the dependence of the stress-strain state of the rope with local violations of the cable base on changes in mechanical properties of rubber provides the ability to predict the stress state of the rope to improve safety and reliability of rubber traction with a long service life.

Use of exhausted biosorbent ash as ecofriendly filler in natural rubber

Biosorption is a promising cost-effective clean-up technology for treating wastewater laden with heavy metals. However, the commercial application of biosorption technologies has been limited because a large amount of toxic waste is left behind in this process. The post-sorbents need to be handled in a way that does not negatively affect the environment. In this research, one possibility to solve this problem was proposed and developed: incineration of used adsorbent, followed by the use of the obtained ash as a filler in rubber production. The results showed that the addition of biosorbent ash does not significantly affect the rubber mechanical and elastic properties. The ash addition affected only the beginning of the vulcanization by increasing the activation energy of the curing chemical reaction. This property can be used to prevent the premature start of vulcanization. Furthermore, it was determined whether and to what extent the ash-filled rubber releases metal ions in contact with water. Results showed that the amount of copper leached from rubber samples was negligible compared to the copper that remained permanently built in the rubber. Therefore, this novel approach to utilizing saturated biosorbents as rubber fillers is acceptable from the environmental safety perspective. © 2022 Society of Industrial Chemistry.

Seismic performance of Unbonded Fiber-Reinforced Elastomeric Isolators (UFREI) made by recycled rubber. Influence of suboptimal crosslinking

Seismic base isolation is considered effective to reduce the vulnerability of structures and it represents an optimal retrofitting solution in terms of reliability and effectiveness. Nowadays, one of the most promising devices is the Unbonded Fiber Reinforced Elastomeric Isolator (UFREI), which is considered a low-cost device, thanks to its lightweight, easy installation, and the total absence of steel. The rubber used to assemble the devices must be vulcanized correctly to create the polymer crosslinking to be ready for structural application. All rubber mechanical properties are strongly affected by curing temperature and curing time. In this paper, a series of experimental tests and numerical analyses have been performed to investigate the influence of crosslinking on the seismic performance of UFREIs made of regenerated Ethylene Propylene Diene Monomer (EPDM) combined with glass fiber reinforcement. Two prototypes have been considered, one vulcanized correctly at 150 °C for 40 min and the other at 130 °C for 40 min. Results obtained from Finite Element (FE) cyclic shear tests analysis and nonlinear time history analyses of a preliminary structural application have shown that the devices vulcanized at 130 °C for 40 min, although having suboptimal crosslinking density, are suitable to isolate low-rise masonry buildings properly.

Vulcanization degree influence on the mechanical properties of Fiber Reinforced Elastomeric Isolators made with reactivated EPDM

Rubber is well known as the basic material for some structural devices, such as seaport fenders and seismic isolators. In practice, to seismically isolate a structure it is necessary to interpose between the foundation and the superstructure a rubber device that increases the period of the superstructure, a feature that allows the structure to be "transparent" to the seismic excitation. A seismic isolator is constituted typically by a package of several rubber pads 1–2 cm thick vertically interspersed with either steel laminas or FRP dry textiles suitably treated. In this latter case the isolator is called FREI (Fiber Reinforced Elastomeric Isolator). FREIs exhibit light weight, easy installation and low cost. In this study, recycled rubber in the form of reactivated EPDM has been used to produce very low cost FREIs, combined with glass fiber reinforcement. To be ready for structural application, the rubber used must be vulcanized correctly to properly create the polymer crosslinking. However, all rubber mechanical properties are strongly affected by curing temperature and curing time. Here, the mechanical properties of a typology of FREI conceived and produced by the authors in prototypes are evaluated through a series of experimental tests and numerical computations, taking into account the different levels of vulcanization degree. Shore A hardness test, uniaxial tensile test, and relaxation test have been conducted and verified through Finite Element (FE) modeling. All collected data allow to precisely determine the curing time and temperature to use in the industrial production to obtain optimal output mechanical properties for FREIs.