Reinforcement Of Rubber Research Articles

High-Performance Nitrile Butadiene Rubber Composites with Good Mechanical Properties, Tunable Elasticity, and Robust Shape Memory Behaviors

Considering technical requirements in the oil industry, the reinforcement of nitrile butadiene rubber (NBR) becomes an important issue. In this article, dual cross-linking networks, composed of cov...

Roles played by novolac resin on rubber compounding, reinforcement and nonlinear rheological behaviors

Reducing the energy consumption of rubber compounding and mediating nonlinear rheological responses of rubber nanocomposites are of great significance in the rubber industry. Herein a low glass transition temperature novolac type phenol-formaldehyde (PF) resin was investigated as a secondary filler that can not only reduce input mechanical compounding power but also be able to reinforce rubber in combination with carbon black (CB). Comparative studies about reinforcement and nonlinear rheological behaviors were performed for compounds with CB, PF or both. It is shown that a partial replacement of PF can act in synergism in the thermal stabilities and take similar reinforcement effect as CB-filled compounds below and above glass transition temperature of PF. Elastic and viscous nonlinearities of dual filler compounds can be effectively retarded and lessened above glass transition temperature of PF because of reduced strain amplification effect.

Synergistic Effect of Calcium Carbonate and Biobased Particles for Rubber Reinforcement and Comparison to Silica Reinforced Rubber

Silica is a standard commercial filler to reduce rolling resistance of tires. The co-filler of nano-size calcium carbonate and bio-based particles also produce reinforced rubber with similar tensile properties and rolling resistance as silica reinforced rubber. A synergistic effect between calcium carbonate and soy protein nanoparticles was observed to produce reinforced rubber with good tensile properties and low rolling resistance. The protein increases the effective crosslink density and moduli of calcium carbonate reinforced rubber. Stearic acid coated calcium carbonate particles have a greater reinforcement effect than the uncoated calcium carbonate particles. Mechanical properties of the composites can be adjusted through the complimentary effect of these two fillers. The composite that contains 60% protein and 40% coated calcium carbonate has mechanical properties comparable to that of the silica reinforced rubber. The temperature and strain dependent dynamic mechanical properties, as well as the stress relaxation behaviors of these rubbers, reveal synergistic effect between the co-fillers. This development demonstrates an economical method to produce useful reinforced rubbers.

Contribution of filler–filler interaction and filler aspect ratio in rubber reinforcement by silica and mica

The reinforcement degree offered by silica as a spherical filler with low aspect ratio and high filler–filler interaction was compared with mica as a platelet filler with higher aspect ratio and lower filler–filler interaction. By replacing half of the carbon black with silica or mica in a typical formulation, rubber composites were prepared and their properties were evaluated under two conditions: In the first one, the impact of increasing the amount of a chemical surface modifier, namely silane TESPT (bis triethoxysilylpropyl tetrasulfide), was investigated and in the second one, the increasing amount of a physical modifier namely DPG (diphenyl guanidine) on the performance of the two fillers was explored. The resulting composites were subjected to physico-mechanical experiments including the bound rubber, tensile test, and the dynamic mechanical thermal analysis (DMTA). Results indicated that the greater amount of filler–filler interaction resulting from the higher SiO2 and hydroxyl content in silica has a dominating role over the aspect ratio of mica which is then led to a remarkable difference in their bound rubber. However, the mica-containing composites were capable of competing with silica when the DPG was used. Nevertheless, the compound only containing carbon black with 19.7 MPa of tensile strength and 24.4 kgf/cm of tear strength showed the best mechanical properties among other fillers, and by replacing 30 phr carbon black, these properties decreased approximately 15 ± 3%. Based on DMTA findings, promising data were obtained for the mica-reinforced rubbers with regard to the tire application.

Impact of Gamma Radiation and Rice Husk Nanosilica on the Physico-Mechanical Properties of Styrene Butadiene Rubber/Natural Rubber Blend

Silica is the major inorganic constituent of the rice husk. High-surface area amorphous silica, Extracted Nanosilica (ENS), was developed by washing out the rice husk, followed by combustion and finally chemically treated. ENS was characterized by FTIR, XRD and TEM techniques. Reinforcement of natural rubber (NR)/styrene butadiene rubber (SBR) blend with varying ratio of ENS, namely 5, 10 and 20 phr, and separately with 20 phr Hisil (commercial silica) was established. Vulcanization of the produced composites was applied by gamma irradiation at a total dose range from 50 to 200 kGy. The radiation-cured nanocomposites were examined via mechanical, physical and thermal investigations. The SEM micrographs affirmed the homogenous distribution of silica particles throughout the polymer matrices. The results ensured noticeable enhancement in the investigated properties of the nanocomposites.

Cellulose Nanofibers Isolated from the Cuscuta Reflexa Plant as a Green Reinforcement of Natural Rubber.

In the present work, we used the steam explosion method for the isolation of cellulose nanofiber (CNF) from Cuscuta reflexa, a parasitic plant commonly seen in Kerala and we evaluated its reinforcing efficiency in natural rubber (NR). Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Thermogravimetric analysis (TGA) techniques indicated that type I cellulose nanofibers, with diameter: 10–30 nm and a 67% crystallinity index were obtained by the proposed method. The results showed that application of CNF in NR based nanocomposites resulted in significant improvement of their processing and performance properties. It was observed that the tensile strength and tear strength of NR/CNF nanocomposites are found to be a maximum at 2 phr CNF loading, which corresponds with the studies of equilibrium swelling behavior. Dynamic mechanical analysis, thermogravimetric analysis, and morphological studies of tensile fractured samples also confirm that CNF isolated from Cuscuta reflexa plant can be considered as a promising green reinforcement for rubbers.

On factors affecting surface free energy of carbon black for reinforcing rubber

Abstract The surface activity of carbon black (CB) is an important factor affecting the reinforcement of rubber. The quantitative determination of the surface activity (surface free energy) of CB is of great significance. A simplified formula is obtained to determine the free energy of CB surface through theoretical analysis and mathematical derivation. The surface free energy for four kinds of industrial CBs were measured by inverse gas chromatography, and the influential factors were studied. The results showed that the aging time of the chromatographic column plays an important role in accurate measurement of the surface free energy of CB, in comparison with the influences from the inlet pressure and carrier gas flow rate of the chromatographic column filled with CB. Several kinds of industrial CB were treated at high temperature, and the surface free energy of CB had a significant increase. With the increase of surface free energy, the maximum torque was decreased significantly, the elongation at break tended to increase, the heat generation of vulcanizates was increased, and the wear resistance was decreased.

A DEM method for simulating rubber tyres

Recently, recycled rubber tyres were found to be an economical and environmental-friendly reinforcement material in geotechnical engineering. Although the use of rubber tyre-reinforced soil has become increasingly popular, there is still a lack of a robust and systematic method to model rubber tyres when using the discrete-element method (DEM) to investigate the stress-strain responses. In this paper, DEM rubber tyres are simulated by bonding regular-packed balls, and numerically tested under tensile force using the particle flow code in three dimensions. When comparing the effects of different packings on the sample, using Young's modulus and Poisson's ratio, it was found that only body-centred-cubic packing could achieve a Poisson's ratio of 0·5 representing no volume change during the deformation of rubber. The difference between uniaxial compression and tension simulations was also compared as well as the influences of particle overlapping, particle radius and sample aspect ratio on the mechanical response of the tyre model. Finally, the DEM parameters were set to match the experimental Young's modulus data. This proposed DEM rubber tyre strips model could be a basis to study other rubber reinforcements such as tyre chips and shreds, irregular rubber buffings and granulated rubber.

Repeated vs. Acute Exposure of RAW264.7 Mouse Macrophages to Silica Nanoparticles: A Bioaccumulation and Functional Change Study.

Synthetic amorphous silica is used in various applications such as cosmetics, food, or rubber reinforcement. These broad uses increase human exposure, and thus the potential risk related to their short- and long-term toxicity for both consumers and workers. These potential risks have to be investigated, in a global context of multi-exposure, as encountered in human populations. However, most of the in vitro research on the effects of amorphous silica has been carried out in an acute exposure mode, which is not the most relevant when trying to assess the effects of occupational exposure. As a first step, the effects of repeated exposure of macrophages to silica nanomaterials have been investigated. The experiments have been conducted on in vitro macrophage cell line RAW264.7 (cell line from an Abelson murine leukemia virus-induced tumor), as this cell type is an important target cell in toxicology of particulate materials. The bioaccumulation of nanomaterials and the persistence of their effects have been studied. The experiments carried out include the viability assay and functional tests (phagocytosis, NO and reactive oxygen species dosages, and production of pro- and anti-inflammatory cytokines) using flow cytometry, microscopy and spectrophotometry. Accumulation of silica nanoparticles (SiO2 NP) was observed in both exposure scenarii. However, differences in the biological effects between the exposure scenarii have also been observed. For phagocytosis, NO production and Tumor Necrosis Factor (TNF) release, repeated exposure tended to induce fewer effects than acute exposure. Nevertheless, repeated exposure still induces alterations in the macrophage responses and thus represents a scenario to be tested in detail.

BETTER BALANCE OF SILICA-REINFORCED NATURAL RUBBER TIRE TREAD COMPOUND PROPERTIES BY THE USE OF MONTMORILLONITE WITH OPTIMUM SURFACE MODIFIER CONTENT

ABSTRACT Reinforcement of silica in tire tread compounds is known to reduce hysteresis or energy loss, which leads to a production of energy-saving tires. Even though silica–silane technology has been well established, further development to enhance its performance is still needed. One of the approaches is to use hybrid or dual filler. The use of silica-organomodified montmorillonite (MMT) dual filler in the reinforcement of natural rubber (NR) truck tire tread compounds is investigated. The NR-MMT master batches were prepared by using the in situ organomodified and latex compounding method. Because the surface-modifying agent or surfactant is a key factor in determining the level of MMT dispersion in the rubber matrix, the effect of quaternary amine salt (Q) contents on mechanical and dynamic properties of NR tread compounds reinforced by silica-MMT was studied. The results revealed that MMT and Q can effectively reduce the filler–filler interaction and complex viscosity owing to a good dispersion of MMT and silica in the NR matrix and Q, which acts as a dispersing agent in addition to the silane coupling agent used in the compound, leading to improvement in tensile, abrasion resistance, and dynamic mechanical properties with an increasing amount of Q. Furthermore, at the optimum content of the surfactant used (36 wt%), the silica-MMT–reinforced NR exhibited improved tensile strength (+4%), wet grip, and rolling resistance, respectively, as indicated by loss tangent at 0 °C (+6%) and 60 °C (−15%), while maintaining a modulus at 300% strain and abrasion resistance as compared with the silica-NR reference compound. Such a dual-filler system demonstrates its potential use for tire treads with better performance.

Advances in Properties of Rubber Reinforced Soil

The accumulation of waste tires is a global resource and environmental problem. The landfill or incineration of tires will infiltrate toxic chemicals into the surrounding environment, which poses a serious ecological threat to the environment. A large number of studies have shown that waste tires can be used in geotechnical engineering, which provides a good idea for the recycling of waste tires. Up to now, researchers have tested the performance of soil mixed with waste tires by dynamic triaxial test, California load ratio test, unconfined compression test, direct shear test, consolidation test, and expansive force test. The results show that the stability and strength of the soil can be enhanced by adding about 20% rubber particles to the expansive soil, and the expansion, contraction, and consolidation characteristics of the expansive soil can be significantly improved. Rubber can improve the mechanical properties and deformation properties of sand. The rubber sand with a rubber content of 30% is often used as the isolation layer of middle and low buildings. However, it remains to be seen whether it is sustainable and durable to use waste tire rubber to improve soil properties and whether the chemical composition of waste tire rubber will have adverse effects on soil. So, more researchers are encouraged to look into this question. Here, we review the method and effect of rubber reinforcement technology with scrap tires and introduce the practical application of rubber reinforcement technology in engineering, such as specific engineering projects for retaining wall, road filling, shock absorption, and vibration isolation. This review will be of great significance and broad prospects for the reuse of waste tires and the development of geotechnical engineering.

Synergetic effect of rubber on the tensile and flexural properties of graphene based epoxy-carbon fiber hybrid nanocomposite

The interaction effects of rubber addition on the tensile and flexural characteristics of hybrid composites of Epoxy-carbon fiber with Graphene as nanofiller were studied. Bisphenol resin was used as matrix. The epoxy-carbon fiber composite was modified with 0.1, 0.2 and 0.3 wt% of graphene. The specimens with 0.1% graphene exhibited significant rise in tensile and flexural strength whereas on further addition of graphene with 0.2 and 0.3% the strength improved marginally compared to epoxy-carbon fiber composite. 10, 20 and 30% by weight natural rubber in liquid form was added to epoxy-carbon fiber with 0.1% graphene, which further enhanced the tensile and flexural characteristics of the hybrid composite. The specimens with 10% rubber reinforcement exhibited a nominal improvement in the tensile and flexural strength of the hybrid composite whereas the specimens with 20% rubber showed acceptable rise in the tensile and flexural strength. Upon further addition of rubber by 30% the strength decreased marginally. The SEM results for different configurations were analyzed to study the morphological and interfacial interactions.

Surface modification of nano-sized carbon black for reinforcement of rubber

AbstractThe standard sample IRB7# of nano-sized carbon black was reated by different methods, including washing by alcohol, toluene, water, the emulsion of toluene and water, and heating. Surface activity of the obtained nanoparticles was measured using inverse gas chromatography. The results showed that the dispersion free energy could be significantly increased after heating. The surface activity of three kinds of industrial carbon black was studied after heat treatment at different temperature. The results indicated that surface activity, iodine adsorption number and nitrogen surface area values of carbon black nanoparticles increased with the increase of temperature. However, the dibutyl phthalate adsorption value maintained nearly constant. The performance test of rubber showed that with the increasing heat treatment temperature of carbon black, 300% modulus of rubber increased before 450°C and decreased after 450°C.

Local glass transition of polyisoprene induced by graphene planes observed in silico through atomistic molecular dynamics simulations

A study on the molecular mechanisms of natural rubber reinforcement due to the addition graphene planes was carried out by molecular dynamics simulations. Simulations of pure natural rubber (Polyisoprene; PI) and Polyisoprene-graphene composite (PI-GRA) were performed and analyzed for their glass transition temperatures (Tg). In the simulations, simulated annealing technique was used to change the temperature from 100 K to 300 K in order to observe the glass transition from the point where the sudden increase in volume and sudden decrease in density were observed. Glass transition temperature (Tg) from the molecular dynamics trajectory of pure PI was 207.9 K, close to the value Tg = 211 K obtained from the experiment. Also, we found that glass transition temperature (Tg) increased to 220.1 K when adding graphene planes into the PI matrix. In addition, further analysis of MD trajectories showed that the overall density of pure 16-mer cis-1, 4-polyisoprene at low temperature (100 K) is higher than the density at high temperature (300 K) and the threshold density for glass transition was 929.4 kg/m3. For PI-GRA at 100 K, density of the whole system was higher than the threshold density, which showed that the whole polymer was in glass phase. However, at 300 K, the network of PI molecules nearby the graphene planes were orderly organized and possessed higher density than the threshold density, which showing the properties of glass. In the middle area, PI molecules were arranged disorderly and has a lower density than the threshold, showing the properties of rubber.

Hyperelastic characteristics of graphene natural rubber composites and reinforcement and toughening mechanisms at multi-scale

In order to meet the increasing demand of damping and shock absorption materials, graphene-based rubber composites are considered as a candidate material because of their excellent strength and toughness. Here, we propose a small and excessive amount of 3-aminopropyl triethoxy silane (APTS) modified graphene oxide as a functional composite material for filling and reinforcing natural rubber, and we also prepare the corresponding natural rubber composites containing graphene oxide (go) and reduced graphene oxide (rgo). Compared with natural rubber filled with carbon black, the crosslinking density and mechanical properties of the composites containing graphene prepared in this paper improved significantly. The strengthening and toughening mechanism of APTS modified graphene oxide filled composites revealed at the micron, nano and even molecular level by FTIR, AFM and SEM characterisation. Notably, by comparing the surface RMS roughness of graphene oxide edited with a small and excessive amount of APTS, we find that the higher the surface roughness of graphene, the more obvious the effect of strengthening and toughening after compounding with natural rubber. These results will be helpful for the application of graphene composites in rubber damping materials.

Geotechnical Properties of Rubber Reinforced Cemented Clayey Soil

This paper focuses on the effect two forms of waste rubber tyres of granulate (Rg) and fibre (Rf) categories on the compaction–strength–consolidation–swell–durability behaviour of uncemented/cemented clayey soil. The effect of incorporation of five proportions 0%, 2.5%, 5%, 7.5% and 10% Rg/Rf (by weight of soil) and three proportions 0%, 3% and 6% cement (by weight of soil) was assessed. Reduction in maximum dry unit weight (γmax) and optimum water content (ωopt) of clayey soil and cemented clayey soil was observed with the incorporation of ruuber granulates (Rg) and rubber fibres (Rf). Both unconfined compressive strength (UCS) and split tensile strength (STS) of the clayey soil were primarily controlled by the amount of cement and waste rubber tyres and it was found to be decreased with the enhancement in rubber content. But addition of Rg and Rf was found to improve the ductility and strain hardening behaviour of cemented clayey soil, prosperously under unconfined compression. Inclusion Rg was found to be ineffective to overshadow the brittleness of the cemented clayey soil subjected to tensile loads. The inclusion of higher rubber content had lowered the strength of cemented significantly. Decline in the California bearing ratio (CBR) value, swelling pressure (σs) and increment in the compression index (Cc) and weight loss during wet/dry cycles were observed with the incorporation of Rg and Rf in cemented clayey soil. The results of all performed tests were cross checked and compared with various Indian standards to reach at the optimum dose of Rg and Rf that can be added to cemented clayey soil for its possible applications in back filling, construction of embankment (for rural roads), sub-grade course, sub-base course and slide slope of canal. The form of waste rubber tyre i.e. Rg and Rf had significant effect on the geotechnical characteristics of cemented clayey soil. Overall, Rf had outperformed the Rg, considering all evaluated geotechnical properties. Maximum dose of Rg and Rf to be added in cemented clayey soil should not be more than 5% and 7.5%, respectively.

Particle packing in bimodal size carbon black mixtures and its effect on the properties of styrene-butadiene rubber compounds

Particle packing, together with other filler characteristics, can be considered as an important structural parameter of fillers, affecting on the properties of rubber compounds. For this purpose, N220 and N550 carbon blacks with nearly similar structure and surface chemistry but different particle sizes were selected. N220/N550 showed the maximum packed density at the composition 35/65 according to the accepted theory for bimodal packing of spheres. A correlation between the packing behavior of carbon blacks mixtures and physical, electrical and rheological behaviors of filled rubber compounds was investigated. A synergic effect in compounds properties was observed before the vulcanization reaction at the maximum packed composition of carbon-blacks. The synergic effect was attributed to the dense and highly immobilized rubber trapped inside packed structure of carbon blacks aggregates, but it didn't appear for the vulcanizates due to the adverse effect of immobilized rubber on the chemical cross-link density formed during vulcanization reaction. • Particle packing is an important structural parameter in rubber reinforcement. • There is a correlation between particle packing and the properties of filled rubber compounds. • A synergic effect in properties was observed at the maximum packed composition of fillers before vulcanization. • The synergic effect was due to the highly immobilized rubber trapped in the filler network. • The synergic effect was absent in some properties after vulcanization.

Nonsolvent-assisted surface modification of silica by silane and antioxidant for rubber reinforcement

Abstract To improve the reinforcing efficiency of silica (SiO2) nanoparticles for rubber and make the treatment procedure easy to commercialize in industrial level, antioxidant 2, 2′-methylenebis (6-tert-butyl-4-methyl-phenol) (2246) and silane were utilized to modify SiO2 via a nonsolvent-assisted process. Antioxidant 2246 was chemically grafted on the surface of SiO2 with the aid of silane coupling agent and performed better than free antioxidant in protecting rubber from thermo-oxidative aging due to the elimination the so-called “blooming” defects. Moreover, the antioxidant and silane modified SiO2 (SiO2-s-2246) was much better than modified SiO2 (m-SiO2) only by silane and unmodified SiO2 in dispersion and compatibility with styrene-butadiene rubber (SBR) based on the results of electron microscope observations, contact angle and bound rubber. Therefore, SBR/SiO2-s-2246 composites exhibited higher mechanical strength than SBR/m-SiO2 or SBR/SiO2 composites. For instance, SBR/SiO2-s-2246 composites with better elasticity exhibited an increase of 48% in tensile strength compared with SBR/m-SiO2 composites. The reinforcing mechanism of SiO2-s-2246 and m-SiO2 was also investigated based on the large strain behavior and swelling Gibbs free energy of SBR composites, which may be instructive for the rational filler surface modification.

Mechanical properties and microstructure characterization of natural rubber reinforced by helical carbon nanofibers

Reinforcement of natural rubber (NR) was achieved by a novel kind of carbon filler, helical carbon nanofibers (HCNFs). The good interface bonding between HCNFs and NR matrix was confirmed by the analysis of transmission electron microscopy, scanning electron microscopy and dynamic mechanical analyzer. The tensile and dynamic mechanical properties of HCNFs/NR nanocomposites with the filler loading of 1–5 phr were studied. When the filler loading is 5 phr, HCNFs/NR nanocomposites have a significant enhancement in the modulus at 300% strain (464% and 163% higher than pure NR and N330/NR, respectively), storage modulus (83.5% and 82% higher than pure NR and N330/NR, respectively) at 0 °C, with a small decrease in elongation at break. The unique carbon coil structure and abundant surface oxygen-containing functional groups of HCNFs play a critical role in the formation of good interface bonding between HCNFs and NR matrix. This work can provide guidance for the development of HCNFs filled rubber materials with excellent mechanical properties.

Rigid nanoparticles promote the softening of rubber phase in filled vulcanizates

Enhanced mechanical softening accompanying nanoparticles reinforcement of rubber is an important source of energy dissipation and heat buildup of industrially engineered elastomers. Its mechanism previously assigned to damages in the filler network, rubber-filler interface and rubber phase remains controversial in more than 70 years. Through investigating the typical Payne effect of styrene-butadiene rubber gum and its vulcanizates as well as silica filled compounds and vulcanizates and the Mullins effect of unfilled and filled vulcanizates, we herein evidence that the filler-promoted softening of the rubber phase softens the filled elastomer nanocomposites. Especially we show that the Mullins effect is relevantly involved in the disentanglement/re-entanglement of dangling chains superposed on the entropically elastic network of the rubber phase. This paper clarifies that the mechanism of nonlinear mechanical softening for filled rubber compounds and vulcanizates should be rooted in macromolecular chains in the entanglement network (gum and filled compounds) or long dangling chain in non-ideally crosslinked network (vulcanized gum and filled vulcanizates), rather than damages involved in the “filler network” or filler-rubber interface. This suggests that adjusting the nonideally crosslinked network structure of viscoelastic rubber matrix should be able to optimize the use performance of the rubber nanocomposite products.