Blends of ultrasonically devulcanized tire-curing bladder and butyl rubber

The devulcanization of the butyl rubber based tire-curing bladder was carried out with a grooved barrel ultrasonic extruder. The devulcanized rubber was blended at different ratios with the carbon black filled virgin butyl rubber and cured. The rheological and mechanical properties, as well as gel fraction and crosslink density of the revulcanized rubber and vulcanizates of blends have been measured. The blend of ground tire-curing bladder and carbon black filled butyl rubber has also been prepared for comparison purpose. Compared to the blend containing the ground rubber, compounding of the blends containing the devulcanized bladder were easier and their vulcanizates had smoother surface. In addition, the vulcanizates containing devulcanized tire-curing bladder and virgin rubber showed substantially improved mechanical properties than the vulcanizate of the devulcanized rubber alone.     

耐高温硅橡胶的配方研究

为提高硅橡胶的耐高温性能,确定最佳的实验配方,以乙烯基硅橡胶为基础胶,八氢基笼型倍半硅氧烷(T_8H_8)为交联剂,白炭黑为补强填料,纳米级氧化锡为耐热填料,制备出一种耐高温硅橡胶.该配方中T_8H_8为自行合成的耐高温硅橡胶交联剂,通过红外光谱(FTIR)、X射线衍射(XRD)、核磁共振氢谱(1HNMR)对T_8H_8结构进行表征,探究了不同配方对硅橡胶耐热性能的影响.结果表明,当乙烯基硅油用量为100 phr,T_8H_8中Si—H与乙烯基硅橡胶中Si—Vi的摩尔比为4∶1,白炭黑添加量为15 phr,氧化锡添加量为8 phr时,硅橡胶的初始分解温度达到489.77℃,拉伸强度为4.06 MPa,剪切强度1.69 MPa.     

Use of styrene butadiene rubber industrial waste devulcanized by microwave in rubber composites for automotive application

The aim of this work was to develop and characterize styrene butadiene rubber (SBR) composites filled with SBR industrial scraps (SBR-r) devulcanized by microwave. The SBR-r was ground under ambient conditions and subjected to microwave exposure for 1, 2 and 3 min. The composites were developed by the incorporation of 80 phr (parts per hundred of rubber) of the devulcanized SBR-r into the rubber matrix and subsequent revulcanization. The rheometric and physical–mechanical properties (shore A hardness, compression set, tensile and tear strength) were determined. The samples were submitted to two types of accelerated aging processes, in an air oven (thermo-oxidation) and an artificial weathering test in a UV chamber (photo-oxidation). The results were compared with a control sample submitted to the same conditions. For further application in automotive profiles, the set of results indicated that the best performance was achieved by the composite containing SBR-r devulcanized for 2 min in a microwave. For this composite, the changes in the chemical characteristics after aging were evaluated with cross-link density and Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy (ATR–FTIR) analyses. The results revealed that the aging mechanism was dependent on the presence of SBR-r and on the time of aging. The cross-link density analysis confirmed the occurrence of cross-link scissioning at shorter aging times and the formation of additional cross-linking in the postcure process. The ATR–FTIR results indicated an oxidative process occurring on the surface of the composites for both aging processes. Moreover, artificial weathering presented a more pronounced change in the chemical structure of the samples.     

Gamma irradiation aging of NBR/CSM rubber nanocomposites

The effect of gamma-irradiation on the acrylonitrile butadiene/chlorosulphonated polyethylene rubber blends (NBR/CSM) based nanocomposites containing carbon black (CB) and silica filler (Si) were investigated by TG-DTG and ATR-FTIR techniques. The silica (with primary particle size of 22 nm) was added in content of 0, 10, 20 and 30 phr and carbon black (with primary particle size 40–48 nm) was added in content of 30 phr and rubber blend compounds were prepared. The obtained elastomeric materials were aging to different γ-irradiation doses (100, 200 and 400 kGy). The cure and mechanical properties of obtained nanocomposites were determined. Incorporating 20 phr of silica to the control NBR/CSM rubber blends containing 30 phr CB resulted 152% increase in tensile strength, 116%, in elongation at break and 142% modulus at 100% elongation, according to synergistic effect between the fillers. FTIR measurements of aged samples estimated the formation of alcohols, ethers and small amounts of lactones, anhydrides, esters and carboxylic acids after exposure to lower doses of γ-radiation (100 kGy). On the basis of the obtained spectra the formation of shorter polyene sequences and aromatic rings in aged elastomeric samples are assumed. The results show that 30 phr of carbon black (CB) and 20 phr of silica are needed for the best gamma aging resistance of NBR/CSM rubber nanocomposites. The result of radiation exposure is decrease in mechanical properties. The dose at which ultimate mechanical properties decreased was at 200 kGy. TG-DTG measurements estimated decrease in thermal stability of gamma-irradiated NBR/CSM rubber blend based nanocomposites. Silica reinforced NBR/CSM rubber blend had better radiation resistant than carbon black. Rough and heterogeneity of fracture surfaces has been observed for NBR/CSM rubber blends filled with silica. More uniform morphology of fracture surfaces according to high polymer–filler interaction and low filler–filler interaction has been observed for CB/Si filled NBR/CSM rubber blend.     

The role of tackifiers on the auto-adhesion behavior of EPDM rubber

The article describes the effect of hydrocarbon (HC) and coumarone-indene (CI) resin tackifiers on autohesion behavior of ethylene propylene diene polymethylene (EPDM) rubber. The viscoelastic behavior and nature of compatibility of EPDM/tackifier blends were studied by means of dynamic mechanical analysis. Furthermore, scanning electron microscopy and atomic force microscopy were used to understand the compatibility of the EPDM/tackifier blends. The HC tackifying resin modified the viscoelastic properties of the EPDM rubber in such a way that it behaved as a plasticizer at lower frequency by reducing the storage modulus and filler at higher frequency by increasing the storage modulus. On the contrary, the CI modified EPDM rubber did not show similar behavior; the modulus enhanced throughout the entire frequency range. The viscosity of the matrix was found to be highly governed by the compatibility as well as amount of tackifier present in the blend. In order to explain the tack behavior, several tack governing factors such as green strength, creep compliance, entanglement molecular weight, relaxation time, self-diffusion coefficient, and monomer friction coefficient (ζ₀) were investigated. The tack strength increased with HC tackifier loading up to 24 parts per hundred grams of rubber (phr), beyond which a plateau region was observed. A maximum of 196% improvement was observed at 24 phr HC loaded sample as compared to gum EPDM rubber devoid of tackifier. Conversely, there was a marginal improvement of tack strength (36%) up to 8 phr loading for the system containing CI, beyond which it dropped.     

Enhancing mechanical properties of styrene–butadiene rubber/silica nanocomposites by in situ interfacial modification with a novel rare-earth complex

In this study, a novel rare-earth complex, dithio-aminomethyl-lysine samarium (DALSm), was prepared and then was employed as activator, accelerator, cross-linker and interfacial modifier to improve the mechanical properties of SBR/silica nanocomposites. The results showed that 6 phr DALSm performed a higher vulcanization efficiency than the combination of 5 phr activator zinc oxide (ZnO), 2 phr stearic acid (SA), and 2 phr accelerator diethyl dithiocarbamate zinc (EDCZn). Meanwhile, the XPS and FTIR analysis of DALSm/silica model compounds confirmed that hydrogen bonds and coordination bonds could be formed between DALSm and silica during vulcanization process, which can effectively facilitate the homogenous dispersion of silica particles into SBR matrix and enhance the interface adhesion between rubber matrix and filler. As a consequent, the mechanical properties of SBR/DALSm/silica nanocomposites were substantially improved and much more excellent than those of the SBR/EDCZn/silica nanocomposites containing equivalent filler content. Based on the results of immobilized polymer layer, the reinforcing mechanism of DALSm in SBR/silica nanocomposites was analyzed.     

Nickel and iron nano-particles in natural rubber composites

In this work, the mechanical, electrical, and magnetic properties of natural rubber (NR) composites containing iron or nickel nanoparticles at different percentage varying from 0 to 120 phr (part of magnetic particle per hundred rubber) have been investigated at room temperature. It was found that the optimum concentration of magnetic fillers in NR is 30 phr, which improve the rheometric characteristics and physico-mechanical properties. Magnetic properties of the rubber composites have been investigated using vibrating sample magnetometer (VSM) at room temperature. The magnetic measurements show superparamagnetic behavior for all Ni and Fe nanoparticles percentage. The electrical measurements show a strong dependency of the conductivity on the percentage of magnetic nanoparticles.     

Effect of magnetic nanoparticles on the properties of magnetic rubber

A new kind of magnetic rubber was prepared through conventional rubber mixing techniques on a two-roll mill, in which the magnetic filler was Fe₃O₄ nanoparticles and was surface modified. The effect of Fe₃O₄ nanoparticles’ content on the mechanical and magnetic properties of nature rubber was further investigated. The obtained results of six different compositions for nature rubber with 0, 5, 10, 15, 20 and 25 phr of Fe₃O₄ nanoparticles were compared. It was found that the magnetic rubber has higher magnetic properties and tensile strength, comparing with unfilled nature rubber. The result suggests that when the magnetic filler is nanoparticles and surface modified, the mechanical and magnetic properties of the rubber can be synchronously improved, which is difficult to be observed in previous work.     

Effect of montmorillonite modification on mechanical properties of vulcanized natural rubber composites

Natural rubber-clay composites were prepared by direct polymer melt intercalation. Ca-montmorillonite Jelšovy Potok (JP; Slovakia) and Na-montmorillonite Kunipia-F (KU; Japan) were ion exchanged with octadecyltrimethylammonium (ODTMA) bromide and were used as aluminosilicate fillers. Silica Ultrasil VN3 was used in amount of 15 phr as conventional filler. The effect of clay or organoclay loading from 1 up to 10 phr on the mechanical properties was evaluated from the tensile tests (stress at break, strain at break and modulus M100). Organic modification resulted in an increase of toluene uptake degree for both fillers. While an addition of unmodified KU had no effect on tensile strength and deformation at break, a reinforcing effect was observed for the mixture containing 10 phr of unmodified JP. Both ODTMA modified fillers (KU and JP) exhibited substantial increase in tensile strength and deformation at break; JP proved to be more effective compared to KU also if modified with ODTMA. The highest stress at break and strain at break values for natural rubber composites were obtained with 15 phr of SiO₂ and 10 phr of montmorillonite; however, the effect of exchangeable cation was minor.     

Styrene butadiene rubber/aluminum powder composites—mechanical,morphological and electrical behaviors

Different weight fractions of aluminum (Al) powder viz., 10, 20, 30, 40, 50, 60 and 70 phr were incorporated into styrene butadiene rubber (SBR) matrix. The Al powder filled and vulcanized SBR composites have been characterized for mechanical properties such as tensile strength, tensile modulus and surface hardness. A drastical improvement in tensile strength and tensile modulus with increase in filler content of the composites was noticed. The electrical properties such as dielectric constant, tan delta and dielectric loss were measured for all the four compositions. The effect of volume fraction (0–70 phr) of conducting filler, frequency (100 kHz–30 MHz), temperature (25–75°C) and relative humidity on dielectric constant, dielectric loss and tan delta values of the composites were studied.     

Filler dispersion evolution of acrylonitrile–butadiene rubber/graphite nanocomposites during processing

In this work, acrylonitrile–butadiene rubber/expanded graphite compounds with initial fine dispersion of nanosize graphite were prepared by latex compounding method, and then the dispersion evolution of the graphite during subsequent mixing and vulcanization was carefully investigated by using rubber process analysis, X-ray diffraction and transmission electron microscopy. The results showed that a significant filler network was already formed in the initial compounds because of the nanoscale dispersion and the high width/thickness ratio of graphite even at a content of less than 5 phr. During shearing, the graphite dispersion evolution is strongly related to the initial filler network. The filler network as well as the dispersion could also be obviously altered by changing the curing pressure and temperature during vulcanization, suggesting that the initial fine dispersion of graphite in the rubber/graphite nanocomposites could be maintained by reducing shear and by curing at a higher temperature and at a lower pressure.     

Rubber composites based on graphene nanoplatelets,expanded graphite,carbon nanotubes and their combination: A comparative study

Solution styrene butadiene rubber (S-SBR) composites reinforced with graphene nanoplatelets (GnPs), expanded graphite (EG), and multiwalled carbon nanotubes (MWCNTs) were prepared and the electrical and various mechanical properties were compared to understand the specific dispersion and reinforcement behaviours of these nanostructured fillers. The electrical resistivity of the rubber composite gradually decreased with the increase of filler amount in the composite. The electrical percolation behaviour was found to be started at 15 phr (parts per hundred rubber) for GnP and 20 phr for EG filled systems, whereas a sharp drop was found at 5 phr for MWCNT based composites. At a particular filler loading, dynamic mechanical analysis and tensile test showed a significant improvement of the mechanical properties of the composites comprised of MWCNT followed by GnP and then EG. The high aspect ratio of MWCNT enabled to form a network at low filler loading and, consequently, a good reinforcement effect was observed. To investigate the effect of hybrid fillers, MWCNT (up to 5 phr) were added in a selected composition of EG based compounds. The formation of a mixed filler network showed a synergistic effect on the improvement of electrical as well as various mechanical properties.     

Magnetic and processability studies on rubber ferrite composites based on natural rubber and mixed ferrite

Polycrystalline single phasic mixed ferrites belonging to the series Ni_1–x Zn _x Fe₂O₄ for various values of _x have been prepared by conventional ceramic techniques. Pre-characterized nickel zinc ferrites were then incorporated into a natural rubber matrix according to a specific recipe for various loadings. The processability and cure parameters were then determined. The magnetic properties of the ceramic filler as well as the ferrite loaded rubber ferrite composites (RFC) were evaluated and compared. A general equation for predicting the magnetic properties was also formulated. The validity of these equations were then checked and correlated with the experimental data. The coercivity of the RFCs almost resemble that of the ceramic component in the RFC. Percolation threshold is not reached for a maximum loading of 120 phr (parts per hundred rubber by weight) of the filler. These studies indicate that flexible magnets can be made with appropriate magnetic properties namely saturation magnetisation (M _s) and magnetic field strength (H _c) by a judicious choice of x and a corresponding loading. These studies also suggest that there is no possible interaction between the filler and the matrix at least at the macroscopic level. The formulated equation will aid in synthesizing RFCs with predetermined magnetic properties.     

Use of rice husks as potential filler in styrene butadiene rubber/linear low density polyethylene blends in the presence of maleic anhydride

In the present study, rice husks filled styrene butadiene rubber (SBR)/linear low density polyethylene (LLDPE) 50/50 blends with a compatibilizer, maleic anhydride (MAH) were prepared using a brabender plasti-corder. Virgin SBR/LLDPE blend was also prepared. The physico-mechanical as well as dielectric properties were investigated. Increasing MAH concentrations in SBR/LLDPE blends resulted in an increase in the tensile strength, elongation at break and hardness. After a certain concentration (2.5 phr), a reduction in these properties was found. On the other hand an increase in the dielectric properties as well as in the mass swell in both toluene and oil with MAH was noticed. After certain concentration of rice husk filler (25 phr) an abrupt increase in permittivity ε′ and dielectric loss ε″ was obtained. These results are supported by the mechanical properties measurements. The scanning electron microscopy (SEM) indicates that the presence of MAH increases the interfacial interaction between SBR/LLDPE blends on one hand and also rice husk filler and the blend on the other hand.     

Effect of the microstructure of a filled rubber on its overall mechanical properties

Mechanical behavior of filled rubber is very different from the corresponding unfilled gum rubber. To understand such difference, a multiscale material model of a filled rubber, which combines molecular mechanics, statistical mechanics and micromechanics, has been developed. The model has been used to explore how filler particles and filler–elastomer bond strength influence the overall elastic properties of a filled rubber. The model confirmed the well-established phenomena such as non-uniform strain amplification, but now, the model added much more detailed molecular information such as cross-linking density, bond strength at filler–elastomer interface, etc. to the whole phenomena. This capability enables us to investigate the influences of the factors on the overall mechanical properties of filled rubber. The results revealed that the degree of stretching is significantly amplified in elastomer chains that locate in between the filler particles along the loading direction. The degree of non-uniform stretching increases with filler volume fraction. The fully stretched elastomer chains contribute significantly greater force and stiffness than those that are stretched less. Both the Mullins effect and the Payne effect come from the non-uniform filler size and/or spatial distribution. Reducing non-uniformity of filler size and spatial distribution can decrease the degree of the Mullins effect and the Payne effect. Improving bond strength at filler–elastomer interface can delay the Mullins effect and the Payne effect but cannot eliminate them.     

A new look at rubber-modified asphalt binders

The high-temperature rheological characteristics and the low-temperature fracture properties of asphalt binders containing crumb and devulcanized rubber waste have been investigated. Asphalt binders containing crumb rubber of different mesh sizes, with and without surface modification, and a commercially available binder containing devulcanized rubber, were tested and compared with an unmodified asphalt and three commercially available polymer-modified binders. Interfacial modification of asphalt systems containing crumb rubber was found to give binders that were far superior in their low-temperature performance to commercially available products. The data suggest that a crack-pinning or crack-blunting mechanism is responsible for the increase in toughness found in these systems. A commercially available binder containing devulcanized rubber showed reasonably good high-temperature properties; however, its low-temperature fracture performance was disappointing in that it was not significantly better than that of unmodified asphalt binders.     

Development and characterization of novel EPDM/NR prophylactic waste composites

Ethylene propylene diene rubber (EPDM) is a well-known versatile polymer, which is frequently used in the production of rubber goods based on conventional and specialty polymers. The present paper investigates the role of recycled natural rubber prophylactic waste compared to virgin natural rubber in the development of novel ethylene propylene diene rubber composites. The processing characteristics have been evaluated using a Monsanto rheometer at three different temperatures 150, 160 and 170°C. The cure curves of EPDM compounds have been found to be the resultant of slow curing or marching cure curve of EPDM and that of fast curing S shaped cure curve of natural rubber. The curing properties such as optimum cure time, scorch time and induction time have been found to be decreasing with the loading of prophylactic filler. For most of the cases, the values obtained for compositions with virgin natural rubber (ISNR-5) have been found to be lower than that with prophylactic filler.The cure activating nature of the prophylactic waste in EPDM is higher at higher temperatures. The unaged tensile strength has been increased with the loading of prophylactic filler up to 30 phr. The aged tensile strength and unaged/aged elongation at break have been found to be a maximum at 20 phr prophylactic filler loading. The tear strength has been found to be a maximum at 40 phr. Better performance has been noted in the case of virgin natural rubber filled samples for unaged/aged tensile strength, elongation break and tear strength except at 40 phr loading. The diffusion process in EPDM vulcanizates is found to be anomalous. Crosslink density values determined using Mooney-Rivlin equation agree with the tensile strength values for most of the cases. An increase in the crosslink density has been noted with the thermal aging of the samples.     

NR/CSM/biogenic silica rubber blend composites

Biogenic silica (BSi) was added at different ratios to some polymer blends of polyisoprene rubber (NR) and chlorosulphonated polyethylene rubber (CSM) cured by conventional sulfur system. The reinforcing performance of the filler was investigated using rheometric, mechanical and swelling measurements, differential scanning calorimetry (DSC), thermogravimetric (TGA) and scanning electron microscopy (SEM) analysis. There was a remarkable decrease in the optimum cure time (t_c90) and the scorch time (t_s2), which was associated with an increase in the cure rate index (CRI), with filler loading up to 30 phr in the different blend ratios. The tensile strength and hardness was 4–5 Sh-A higher in the case for the different blend compositions, while the resistance to swelling in toluene became higher. SEM photographs show that the filler is located at the interface between the different polymers which induces compatibilization in the immiscible blends. DSC scans of the filled blends showed shifts in the glass transition temperatures Tg which can be attributed to the improve interfacial bonding between filler and NR/CSM matrix. A higher thermal stability of NR/CSM/BSi composites was detected.     

Facile preparation of graphene nanoribbon filled silicone rubber nanocomposite with improved thermal and mechanical properties

In the present study, graphene nanoribbon was prepared through unzipping the multi walled carbon nanotubes, and its reinforcing effect as a filler to the silicone rubber was further investigated. The results showed that carbon nanotubes could be unzipped to graphene nanoribbon using strong oxidants like potassium permanganate and sulfuric acid. The prepared graphene nanoribbon could homogeneously disperse within silicone rubber matrix using a simple solution mixing approach. It was also found from the thermogravimetric analysis curves that the thermal stability of the graphene nanoribbon filled silicone rubber nanocomposites improved compared to the pristine silicone rubber. Besides, with the incorporation of the nanofiller, the mechanical properties of the resulting nanocomposites were significantly enhanced, in which both the tensile stress and Young’s modulus increased by 67% and 93% respectively when the mass content of the graphene nanoribbon was 2.0 wt%. Thus it could be expected that graphene nanoribbon had large potentials to be applied as the reinforcing filler to fabricate polymers with increased the thermal and mechanical properties.     

Improvement of impact property of natural fiber–polypropylene composite by using natural rubber and EPDM rubber

In this research, vetiver grass was used as a filler in polypropylene (PP) composite. Chemical treatment was done to modify fiber surface. Natural rubber (NR) and Ethylene Propylene Diene Monomer (EPDM) rubber at various contents were used as an impact modifier for the composites. The composites were prepared by using an injection molding. Rheological, morphological and mechanical properties of PP and PP composites with and without NR or EPDM were studied. Adding NR or EPDM to PP composites, a significant increase in the impact strength and elongation at break is observed in the PP composite with rubber content more than 20% by weight. However, the tensile strength and Young’s modulus of the PP composites decrease with increasing rubber contents. Nevertheless, the tensile strength and Young’s modulus of the composites with rubber contents up to 10% are still higher than those of PP. Moreover, comparisons between NR and EPDM rubber on the mechanical properties of the PP composites were elucidated. The PP composites with EPDM rubber show slightly higher tensile strength and impact strength than the PP composites with NR.