Morphology and performance of styrene butadiene rubber filled with modified graphite nanoplatelet and carbon black

In our work, effects of 2‐mercapto‐1‐methylimidazole modified graphite nanoplatelet (MMI–GN) and carbon black (CB) on static and dynamic mechanical properties of styrene butadiene rubber (SBR) composites were studied. MMI–GN is synthesized by ball‐mill process, and the result reveals that π–π interactions existed between MMI and GN. The results demonstrate that the static and dynamic mechanical performances of SBR/CB/MMI–GN composites are significantly improved over these of SBR/CB and SBR/CB/GN composites. Compared with SBR/CB, the tensile strength, tear strength, and modulus at 300% elongation of SBR/CB/MMI–GN–3 are greatly improved by 45%, 27%, and 4%, respectively. And the rolling resistance of SBR/CB/MMI–GN–3 is reduced by 3.7% with remaining almost unchanged in the wet grip property. The superiority of MMI–GN in the enhancement for the overall performance of SBR/CB composites is attributed to the well dispersion of GN throughout the SBR matrix and the enhanced interfacial interactions between GN and the SBR matrix. This work might expedite synthesis of the graphite‐based materials for enhancing rubber composites, and enlarge the potential applications of modified graphite to fabricate the high‐performance rubber composites. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermal behaviour of styrene butadiene rubber/poly(ethylene-co-vinyl acetate) blends

The thermal behaviour of styrene butadiene rubber (SBR)/poly (ethylene-co-vinyl acetate) (EVA) blends was studied by using thermogravimetry (TG) and differential scanning calorimetry (DSC). The effects of blend ratio, cross-linking systems and compatibilization on the thermal stability and phase transition of the blends were analyzed. It was found that the mass loss of the blends at any temperature was lower than that of the components, highlighting the advantage of blending SBR and EVA. The addition of compatibilizer was also found to improve the thermal stability. DSC studies indicated the thermodynamic immiscibility of SBR/EVA system even in the presence of the compatibilizer. This is evident from the presence of two different glass transition temperatures, corresponding to SBR and EVA phases in both compatibilized and uncompatibilized blends.     

Thermal properties in cured natural rubber/styrene butadiene rubber blends

Blends of natural rubber (NR) and styrene butadiene rubber (SBR) were prepared with sulfur and n-t-butyl-2-benzothiazole sulfonamide (TBBS) as accelerator, varying the amount of each polymer in the blend. Samples were analysed by rheometer curing at 433 K until their maximum torque was reached. The miscibility among the constituent polymers of the cured compounds was studied in a broad range of temperatures by means of differential scanning calorimetry, analyzing the glass transition temperatures of the samples. The specific heat capacity of the compounds was also determined. Thermal diffusivity of the samples was measured in the temperature range from 130 to 400 K with a new device that performs measurements in vacuum. The thermal results are explained on the basis of the structure formed during the vulcanization of the samples considering the variation of the crosslink density of each phase. Finally, a serial thermal conduction model that takes into account the contribution of each phase to the thermal diffusivity was used to fit the experimental results.     

Morphology and micromechanical behaviour of styrene/butadiene block copolymers and their blends with polystyrene

The correlation between the morphology and the deformation mechanism in styrene/butadiene block copolymers having modified architecture and in blends with homopolymer polystyrene (hPS) was studied. It was demonstrated that the morphology formation in the block copolymers is highly coupled with their molecular architecture. In particular, the micromechanical behaviour of a star block copolymer and its blends with polystyrene was investigated by using electron microscopy and tensile testing. A homogeneous plastic flow of polystyrene lamellae (thin layer yielding) was observed if the lamella thickness was in the range of 20 nm. The deformation micromechanism switched to the formation of craze-like deformation zones when the average PS lamella thickness changed to about 30 nm and more.     

Film-forming ability and mechanical properties of coalesced latex blends

The film-forming ability of latex blends (hard latex + soft latex) and the mechanical behavior at finite strain of latex blend films (soft matrix with tough inclusions) has been investigated. The maximum weight fraction of hard latex particles (ϕ_max) which still gives rise to transparent and crack-free films has been used as film-forming ability criterion. It was shown that when the T_g of the soft latex is low (T_g(soft) < 0°C), ϕ_max is constant and equal to 0.55 because the film-forming ability is controlled by contacts between hard particles. Nevertheless, the expected effect of T_g(soft) on film-forming ability is observed (i.e., ϕ_max decreases when T_g(soft) increases) when T_g(soft) is above 0°C. From the mechanical behavior point of view, it was shown that the two main parameters controlling the mechanical behavior of latex blend films are: the mechanical properties of the soft polymer because it represents the continuous matrix and the weight fraction of hard latex particles since they enhance the local deformation of matrix under load. However, it was also proven that debounding between the T_g latex particles and low T_g matrix occurs rapidly (at an elongation ratio ≈ 30%) during uniaxial strain experiments and has to be taken into account in order to gain a thorough understanding of the mechanical behavior of these biphasic films. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2093–2101, 1997     

Dynamic mechanical and thermal properties of physically compatibilized natural rubber/poly(methyl methacrylate) blends by the addition of natural rubber‐graft‐ poly(methyl methacrylate)

The dynamic mechanical and thermal properties of natural rubber/poly (methyl methacrylate) blends (NR/PMMA) with and without the addition of graft copolymer (NR‐g‐PMMA) have been investigated. Dynamic mechanical spectroscopy is used to examine the effect of compatibilizer loading on storage modulus (E′), loss modulus (E″) and loss tangent (tan δ) at different temperatures and at different frequencies. The morphology of the blends indicates that the size of the dispersed phase decreased by the addition of a few percent of the graft copolymer followed by a leveling off at higher concentrations. This is an indication of interfacial saturation. Attempts have been made to correlate morphology with dynamic mechanical properties. Various models have been used to fit the experimental viscoelastic results. Differential scanning calorimetry has been used to analyze the glass‐transition temperatures of the blends. The thermal stability of the blends has been analyzed by thermogravimetry. Compatibilized blends are found to be more thermally stable than uncompatibilized blends. Finally the miscibility and mechanical properties of the blends annealed above T_g are evaluated. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 525–536, 2000     

A SAXS and swelling study of cured natural rubber/styrene–butadiene rubber blends

A small‐angle X‐ray scattering (SAXS) and swelling study of natural rubber and styrene–butadiene rubber blends (NR/SBR) is presented. To this aim, specimens of NR and SBR and blends with 75/25, 50/50, and 25/75 NR/SBR ratios (in phr) were prepared at a cure temperature of 433 K and the optimum cure time (t₁₀₀). This time was obtained from rheometer torque curves. The system of cure used in the samples was sulfur/n‐t‐butyl‐2‐benzothiazole sulfenamide. From swelling tests of the cured samples, information about the molecular weight of the network chain between chemical crosslinks was obtained. For all cured compounds, in the Lorentz plots built from SAXS scattering curves, a maximum of the scattering vector q around 0.14 Å^?1 was observed. However, the q position shows a linear‐like shift toward lower values when the SBR content in the SBR/NR blend increases. In pure NR or SBR the q values show a different tendency. The results obtained are discussed in terms of the existence of different levels of vulcanization for each single phase forming the blend and the existence of a third level of vulcanization located in the interfacial NR/SBR layer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2320–2327, 2009     

POSS nanoparticles as a potential compatibilizer for natural rubber/butadiene rubber blends

In this study, it was aimed to investigate octavinyl‐polyhedral oligomeric silsesquioxane (OV‐POSS) incorporation into natural rubber (NR)/butadiene rubber (BR) elastomer blends as a potential compatibilizer. The effects of OV‐POSS loading levels on the thermal, mechanical, morphological, and dynamic‐mechanical properties of elastomer blends were explored. Fourier‐Transform Infrared Spectrometer (FTIR), Temperature Scanning Stress Relaxation (TSSR), and Differential Scanning Calorimetry (DSC) results revealed the conceivable effect of OV‐POSS nanoparticles in the vulcanization through reacting with sulfur and/or elastomers. Scanning Electron Microscope (SEM), X‐Ray Diffraction (XRD), and tensile test measurements supported the improvement of mechanical properties due to homogeneous dispersion at low loading levels. On the other hand, high amount of OV‐POSS incorporation (7 and 10 phr) resulted in a decrease in mechanical properties, owing to the agglomeration of nanoparticles. According to contact angle and Dynamic mechanical analysis (DMA) results, it could be concluded that OV‐POSS nanoparticles were localized at the interface of the elastomers and enabled the compatibilization of immiscible NR/BR blends.     

Effects of thermal annealing on the viscoelastic properties and morphology of bimodal hard/soft latex blends

The effects of thermal annealing on the viscoelastic properties and morphology of films prepared from bimodal latex blends containing equal weight fractions of soft and hard latex particles with controlled sizes were investigated. The thermal and viscoelastic properties of as‐dried and annealed samples were investigated with differential scanning calorimetry and dynamic mechanical analysis (DMA). Throughout the thermal annealing, the latex blend morphologies were also followed with atomic force microscopy and transmission electron microscopy (TEM). A particulate morphology, consisting of hard particles evenly dispersed in a continuous soft phase, was observed in the TEM micrographs of the as‐dried latex blends and resulted in an enhancement of the mechanical film properties at temperatures between the α relaxations of the soft and hard phases in the DMA thermograms. As soon as the thermal annealing involved temperatures higher than the glass‐transition temperature of the hard phase, the hard particles progressively lost their initial spherical shape and formed a more or less continuous phase in the latex blends. This induced coalescence of the hard particles was confirmed by the association of the experimental viscoelastic data with theoretical predictions, based on self‐consistent mechanical models, which were performed by the consideration of either a particulate or cocontinuous morphology for the bimodal latex blends. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2289–2306, 2005     

Morphology and properties of natural rubber with nanomatrix of non‐rubber components

The morphology of natural rubber was observed by transmission electron microscopy. Nanomatrix of non‐rubber components such as proteins and phospholipids was found to be inherently formed in natural rubber, in which natural rubber particles of about 0.5 µm in average diameter were dispersed. The nanomatrix of non‐rubber components disappeared after deproteinization of natural rubber with urea. Stress at break of serum rubber was higher than that of deproteinized natural rubber, while strain at break did not change. When the amount of the non‐rubber components increased, the stress at break became significantly dependent upon the amount of non‐rubber components. Viscoelastic properties of natural rubber were also dependent upon the nanomatrix of non‐rubber components. Storage modulus of natural rubber increased significantly, when the amount of the non‐rubber components increased. Copyright © 2010 John Wiley & Sons, Ltd.     

Morphology and mechanical properties of binary triblock copolymer blends

The influence of the morphology on the mechanical properties of binary styrene–butadiene (SB) triblock copolymer blends of a thermoplastic block copolymer and a thermoplastic elastomer (TPE) with different molecular architectures was studied with bulk samples prepared from toluene. Both block copolymers contained SB random copolymer middle blocks, that is, the block sequence S–SB–S. The two miscible triblock copolymers were combined to create a TPE with increased tensile strength without a change in their elasticity. The changes in the equilibrium morphology of the miscible triblock copolymer blends as a function of the TPE content (lamellae, bicontinuous morphology, hexagonal cylinders, and worms) resulted in a novel morphology–property correlation: (1) the strain at break and Young's modulus of blends with about 20 wt % TPE were larger than those of the pure thermoplastic triblock copolymer; (2) at the transition from bicontinuous structures to hexagonal structures (～35 wt % TPE), a change in the mechanical properties from thermoplastic to elastomeric was observed; and (3) in the full range of wormlike and hexagonal morphology (60–100 wt % TPE), elastomeric properties were observed, the strength greatly increasing and high‐strength elastomers resulting. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 429–438, 2005     

Novel biphasic structured composite prepared by in situ silica filling in natural rubber latex

The sol‐gel reaction of tetraethoxysilane in natural rubber (NR) latex was conducted to produce in situ silica‐filled NR latex, followed by adding sulfur cross‐linking reagents to the latex in a liquid state. The latex was cast and subjected to sulfur curing to result in a unique morphology in the NR composite of a flexible film form. The contents of in situ silica filling were controlled up to 35 parts per one hundred rubber by weight. The silica was locally dispersed around rubber particles to give a filler network. This characteristic morphology brought about the composite of good dynamic mechanical properties. Synchrotron X‐ray absorption near‐edge structure spectroscopy suggested that the sulfidic linkages of the sulfur cross‐linked composites were polysulfidic, S_x (x ≥ 2), and a fraction of shorter polysulfidic linkages became larger with the increase of in situ silica. The present observations will be of use for developing a novel in situ silica‐filled NR composite prepared in NR latex via liquid‐phase soft processing. Copyright © 2011 John Wiley & Sons, Ltd.     

Ionic liquid functionalized graphene oxide for enhancement of styrene‐butadiene rubber nanocomposites

Ionic liquid 1‐allyl‐3‐methyl‐imidazolium chloride (AMICl) is used to fine‐tune the surface properties of graphene oxide (GO) sheets for fabricating ionic liquid functionalized GO (GO‐IL)/styrene‐butadiene rubber (SBR) nanocomposites. The morphology and structure of GO‐IL are characterized using atomic force microscope, X‐ray diffraction, differential scanning calorimetry, X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV‐vis spectra and Raman spectra. The interaction between GO and AMICl molecules as well as the effects of GO‐IL on the mechanical properties, thermal conductivity and solvent resistance of SBR are thoroughly studied. It is found that AMICl molecules can interact with GO via the combination of hydrogen bond and cation–π interaction. GO‐IL can be well‐dispersed in the SBR matrix, as confirmed by X‐ray diffraction and scanning electron microscope. Therefore, the SBR nanocomposites incorporating GO‐IL exhibit greatly enhanced performance. The tensile strength, tear strength, thermal conductivity and solvent resistance of GO‐IL/SBR nanocomposite with 5 parts per hundred rubber GO‐IL are increased by 505, 362, 34 and 31%, respectively, compared with neat SBR. This method provides a new insight into the fabrication of multifunctional GO‐based rubber composites. Copyright © 2016 John Wiley & Sons, Ltd.     

Morphology of peroxide-prevulcanised natural rubber latex: effect of reaction time and deproteinisation

A non-uniform mesh structure, i.e. a dense network near the surface of peroxide-prevulcanised natural rubber latex particles, was observed under transmission electron microscopy. In the initial period of prevulcanisation, the swelling ratio of the latex sheet decreased with longer reaction time while an increase in crosslink density of rubber particles containing polystyrene, prepared using the phase transfer/bulk polymerisation process, was noticed. The modulus of the rubber sheet increased up to maximum crosslinking and thereafter decreased. After removal of proteins from the latex membrane layer, derived from protein-lipid originally existing at the rubber particle surface, could not be detected. The absence of proteins, which act as free radical scavengers, resulted in a rapid diffusion of alkoxy radicals into the rubber phase of deproteinised latex and, therefore, a uniform crosslink distribution inside each particle was obtained.     

Study on combustion property and synergistic effect of intumescent flame retardant styrene butadiene rubber with metallic oxides

Effect of metallic oxides on flame retardancy and the thermal stability of styrene butadiene rubber (SBR) composites based on ammonium polyphosphate (APP) and pentaerythritol (PER) was studied by the limiting oxygen index (LOI), UL 94, the cone calorimeter tests, and thermogravimetry analysis (TGA), respectively. Scanning electron microscopy (SEM) and wide‐angle X‐ray diffraction (WAXD) were used to analyze the morphological structure and the component of the residue chars formed from the SBR composites accordingly. The addition of zirconium dioxide (ZrO₂) at a loading of 3.4 phr could improve the UL 94 test rating of the composite to V‐0. The TGA data illustrated that the metallic oxides could enhance the thermal stability of the SBR/Intumescent flame retardant additives (IFRs) composites at high temperature and increase the residue. Cone calorimeter test gave much clear evidence that the incorporation of ZrO₂ into SBR/IFRs composites resulted in the significant deduction of the heat release rate (HRR) values, and the SEM images showed that the char layers of the composites containing the metallic oxides became more compact. From the WAXD pattern, zirconium phosphate (ZrP₂O₇) may be formed by the reaction between ZrO₂ and APP. Due to the addition of ZrO₂ and the formation of ZrP₂O₇, the flame retardancy of the composite was improved. Copyright © 2009 John Wiley & Sons, Ltd.     

Prevulcanized natural rubber latex/clay aerogel nanocomposites

Natural rubber latex (NR)/clay aerogel nanocomposites were produced via freeze-drying technique. The pristine clay (sodium montmorillonite) was introduced in 1-3 parts per hundred rubber (phr) in order to study the effect of clay in the NR matrix. The dispersion of the layered clay and the morphology of the nanocomposites were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Cure characteristics, thermal stability, and the crosslink density of thermal and microwave-cured NR and its composites were investigated. XRD patterns indicated that both intercalated and exfoliated structures were observed at loadings of 1-3 phr clay. SEM studies revealed that the clay aerogel structure was formed at 3 phr clay loading. The increment in Shore A hardness of nanocomposites compared with pure NR signified excellent polymer/filler interaction and the reinforcing effect of the clay to rubber matrix. This was supported by an increase in maximum rheometric torque and crosslink density. The crosslink density of clay-filled NR vulcanizate was found to increase with the pristine clay content in both thermal and microwave curing methods. However, microwave-cured 2 and 3 phr-filled NR vulcanizates exhibited higher crosslink density than those which were thermal-cured under the same curing temperature. In addition, thermal stability studies showed that pristine clay accelerated the decomposition of NR by showing a slight decrease in onset and peak decomposition temperatures along with clay content.     

Vulcanization kinetics of graphene/styrene butadiene rubber nanocomposites

This paper presents the influence of graphene on the vulcanization kinetics of styrene butadiene rubber （SBR） with dicumyl peroxide. A curemeter and a differential scanning calorimeter were used to investigate the cure kinetics, from which the kinetic parameters and apparent activation energy were obtained. It turns out that with increasing graphene loading, the induction period of the vulcanization process of SBR is remarkably reduced at low graphene loading and then levels off; on the other hand, the optimum cure time shows a monotonous decrease. As a result, the vulcanization rate is suppressed at first and then accelerated, and the corresponding activation energy increases slightly at first and then decreases. Upon adding graphene, the crosslinking density of the nanocomposites increases, because graphene takes part in the vulcanization process.     

Compatibilized natural rubber/recycled ethylene-propylene-diene rubber blends by biocompatibilizer

Biocompatibilizer-based refined, bleached, deodorized palm stearin was successfully used as compatibilizer for natural rubber/recycled ethylene–propylene–diene rubber (NR/R-EPDM) blends. It seems effective in improving the state of cure, tensile properties, as well as the swelling resistance and morphology of the blends, indicating an improvement in compatibility between the NR matrix and R-EPDM rendered by biocompatibilizer. This was clearly verified by the dynamic mechanical properties of the blends. The dynamic responses obtained were clearly corresponding to the swelling result. It proves that the cross-link density plays a major role in the changes of storage modulus and degree of entanglement.     

Investigate on mechanical and tribological properties of solution styrene butadiene and butadiene rubber composites

Solution styrene butadiene and butadiene rubber (SSBR‐BR) composites reinforced with different contents of SiO₂‐graphene have been fabricated firstly. The mechanical properties of the rubber composites were comparatively investigated using tensile tests; experimental results showed that, as an overall trend, the tensile and tear strength increased with increasing contents of SiO₂‐graphene. Most importantly, under the condition of simulating practical working condition, the tribological behavior of SSBR‐BR composites with different contents of SiO₂‐graphene was explored via a universal ring‐plate frictional tester in detail. Combined with the surface roughness of the counterparts, the wear mechanisms were discussed for SSBR‐BR composites under the cement and asphalt counterparts. Finally, several wear mechanisms under different actual working conditions were proposed.     

Preparation of phenyl‐modified natural rubber in latex stage

Phenyl‐modified natural rubber was prepared in latex stage by bromination of deproteinized natural rubber followed by Suzuki‐Miyaura cross‐coupling reaction. First, the bromination of natural rubber was carried out using N‐bromosuccinimide in latex stage. The bromine atom content increased as amount of N‐bromosuccinimide increased. Second, the allylic bromine atom was replaced with a phenyl group using phenyl boronic acid in the presence of a palladium catalyst, according to the Suzuki‐Miyaura cross‐coupling reaction in latex stage. The resulting products were characterized by nuclear magnetic resonance (NMR) spectroscopy. Signal at 7.13 ppm was assigned to the phenyl group of the product, while signals at 3.98, 4.14, and 4.44 ppm were assigned to the remaining allylic brominated cis‐1,4‐isoprene units. The estimated phenyl group content and the conversion of the Suzuki‐Miyaura cross‐coupling reaction were 1.32 and 23.7 mol%, respectively. Glass transition temperature (T_g) of deproteinized natural rubber increased from ?62°C to ?46.7°C, when the phenyl group was introduced into the rubber.