Fracture properties of natural rubber filled with hybrid carbon black/nanoclay

Hybrid carbon black (CB) and nanoclay (NC) in a rubber matrix have provided superior mechanical performances over conventional composites. Yet the fracture and fatigue properties have not been fully explored. In this paper, the mechanical properties of the hybrid-filled natural rubber (NR) were investigated with regard to the tensile strength, fatigue crack growth (FCG) and cut resistance. The ruptured crack tip and the torn surface were studied by using optical microscopy and scanning electron microscopy (SEM), respectively. It was found that the fatigue resistance at large tearing energy and cut strength were enhanced with hybrid filler. Subsidiary cracks were observed at the ruptured tip in rubber with NC. Morphology analysis revealed that the hybrid filler led to a rougher torn surface than rubber with non-hybrid filler. It was proposed that the clay layers constructed a dual phase filler network with CB aggregates. The filler network could cause strength anisotropy in the matrix and introduce more energy dissipation mechanisms to the system, resulting in enhanced fatigue resistance.     

Three‐body abrasive wear behavior of E‐glass fabric reinforced/graphite‐filled epoxy composites

The present article summarizes an experimental study on three‐body abrasive wear behavior of glass fabric reinforced/graphite particulate‐filled epoxy composites. The wear behavior was assessed by rubber wheel abrasion tests (RWAT). The angular silica sand particle sizes in the range 200–250 μm were used as dry and loose abrasives. The tests were carried out for 270, 540, 810, and 1,080 m abrading distances at 22 and 32 N loads. The worn surfaces were examined using scanning electron microscopy (SEM). The results showed varied responses under different abrading distance due to the addition of glass fabric/graphite filler into neat epoxy. It was observed that the glass fabric reinforcement to epoxy matrix (G‐E) is not beneficial to abrasive wear resistance. Further, inclusion of graphite filler to glass fabric reinforced epoxy composite performed poorly resulting in significant deterioration in wear performance while the neat epoxy showed better wear performance. Selected mechanical properties such as hardness, ultimate tensile strength, and elongation at fracture were analyzed for investigating wear property correlations. The worn surface features were studied using SEM to give insight into the wear mechanisms. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Effect of carbon‐based nanoparticles on the cure characteristics and network structure of styrene–butadiene rubber vulcanizate

The network structure of styrene–butadiene rubber (SBR) in the presence of carbon black (CB) with two different structures and multi‐walled carbon nanotubes (MWCNTs) was investigated. Swelling behaviour, tensile properties at various strain rates and cure kinetics were characterized. Experimental data were analysed using the Flory–Rehner model as well as the tube model theory. It is found that the network structure of CB‐filled SBR follows a three‐phase composite model including rigid particles, semi‐rigid bound rubber and matrix rubber. This bound rubber is postulated to be critical for the mechanical and deformational properties, development of crosslinking density in matrix rubber and polymer–filler interaction. For MWCNT‐filled SBR, the bound rubber does not show a substantial contribution to the network structure and mechanical performance, and these properties are greatly dominated by the higher aspect ratio and polymer–filler interaction. Additionally it is deduced that the crosslinking density of matrix rubber increases on incorporation of the fillers compared to unfilled matrix rubber. Copyright © 2012 Society of Chemical Industry     

Effects of palm ash loading and maleated natural rubber as a coupling agent on the properties of palm‐ash‐filled natural rubber composites

Natural rubber composites were prepared by the incorporation of palm ash at different loadings into a natural rubber matrix with a laboratory‐size two‐roll mill (160 × 320 mm²) maintained at 70 ± 5°C in accordance with the method described by ASTM D 3184–89. A coupling agent, maleated natural rubber (MANR), was used to improve the mechanical properties of the natural rubber composites. The results indicated that the scorch time and cure time decreased with increasing filler loading, whereas the maximum torque exhibited an increasing trend. Increasing the palm ash loading increased the tensile modulus, but the tensile strength, fatigue life, and elongation at break decreased. The rubber–filler interactions of the composites decreased with increasing filler loading. Scanning electron microscopy of the tensile fracture surfaces of the composites and rubber–filler interaction studies showed that the presence of MANR enhanced the interfacial interaction of the palm ash filler and natural rubber matrix. The presence of MANR also enhanced the tensile properties and fatigue life of palm‐ash‐filled natural rubber composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and properties of styrene‐butadiene rubber nanocomposites blended with carbon black‐graphene hybrid filler

Graphene has become an attractive reinforcing filler for rubber materials, but its dispersion in rubber is still a big challenge. In this work, a novel carbon black‐reduced graphene (CB‐RG) hybrid filler was fabricated and blended with styrene‐butadiene rubber (SBR) via simple two‐roll mill mixing. The prepared CB‐RG hybrids had a microstructure with small CB agglomerates adsorbed onto graphene surfaces. CB acted as a barrier preventing the RG sheets from restacking even after drying. Homogeneous dispersion of graphene sheets in SBR matrix was observed by the mechanical mixing method based on the application of the CB‐RG hybrid fillers. Dynamic mechanical analysis showed that Tg of the SBR/CB‐RG blend was higher than that of the SBR/CB blend indicating strong interfacial interactions between RG and SBR due to the high surface area of graphene and the π‐π interaction between SBR and graphene. The tensile properties of SBR/CB‐RG composites improved significantly and the volume resistivity decreased compared with the SBR/CB blends. The thermal stability of SBR composites filled with CB and CB‐RG showed slight difference. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41309.     

Viscoelastic properties of natural rubber composites reinforced by defatted soy flour and carbon black co‐filler

Filler mixtures of defatted soy flour (DSF) and carbon black (CB) were used to reinforce natural rubber (NR) composites and their viscoelastic properties were investigated. DSF is an abundant and renewable commodity and has a lower material cost than CB. Aqueous dispersions of DSF and CB were first mixed and then blended with NR latex to form rubber composites using freeze‐drying and compression molding methods. A 40% co‐filler reinforced composite with a 1 : 1 DSF : CB ratio exhibited a 90‐fold increase in the rubber plateau modulus compared with unfilled NR, showing a significant reinforcement effect by the co‐filler. The effect, however, is lower than that observed in the carboxylated styrene–butadiene rubber composites reported earlier, indicating a significant effect from the rubber matrix. The co‐filler composites have elastic moduli between those of DSF and CB reinforced composites. Stress softening and recovery experiments indicated that the co‐filler composites with a higher CB content tend to have a better recovery behavior; however, this can not be simply explained from the recovery behaviors of the single filler (DFS and CB) composites. CB composites prepared by freeze‐drying show a strain‐induced reorganization of fillers. Strain sweep experiment data fit with the Kraus model indicates the co‐filler composites with a higher CB content are more elastic, which is consistent with the recovery experiments. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Biodegradability,mechanical, and thermal properties of thermoplastic starch/cuttlebone composites

This work focused on improvements to the properties of thermoplastic starch (TPS) by using cuttlebone (CB) as the bio‐filler. The effect of CB on the properties of TPS was compared to that of commercial calcium carbonate (CC). The good adhesion achieved between the TPS matrix and the cuttlebone powder produced improvements in the tensile strength of their composites, whereas the tensile strength of TPS/CC composite was lower due to the presence of filler agglomerates. The biodegradation of the TPS and the composites were analyzed by the soil burial test. This showed that cuttlebone decreased the biodegradation rate. The thermal degradation temperatures of TPS, a TPS/CC composite and a TPS/CB composite showed very similar behavior. POLYM. COMPOS., 36:1401–1406, 2015. © 2014 Society of Plastics Engineers     

Action of transfer film in improving friction and wear behaviors of iron‐ and copper‐filled poly(ether ether ketone) composites

The composites of poly(ether ether ketone) (PEEK) filled with micrometer‐sized Cu and Fe particles were prepared by compression molding. The friction and wear behaviors of the composites were examined on a pin‐on‐disc friction‐and‐wear tester by sliding PEEK‐based composites against tool steel at a sliding speed of 1.0 m s⁻¹ and a normal load of 19.6N. Optical microscopic analysis of the transfer film and of the worn pin surfaces and wear debris was performed to investigate the wear mechanisms of the composites. It was found that Cu and Fe used as filler considerably decreased the wear rate of PEEK. A thin, uniform, and tenacious transfer film was formed when Cu was used as the filler, and a nonuniform and thick transfer film was formed when Fe was used as the filler. The transfer film played a key role in increasing the wear resistance of the PEEK composites. Plastic deformation was dominant for wear of PEEK–Cu, while abrasion and adhesion were dominant for wear of PEEK–Fe. Because of the strong affinity between Fe as filler and its identical counterpart in the counterface tool steel surface, the adhesion between the PEEK–Fe composite surface and the counterface tool steel surface was thus severe. This contributed to the generation of a thicker transfer film for PEEK–Fe. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 179–184, 2000     

Effect of nanostructures of modified clay–carbon black on physico‐mechanical,electrical, and acoustic properties of elastomer‐based composites

Elastomeric composites based on nitrile rubber (NBR), carbon black (CB), and organically modified nanoclay (NC) were prepared using a laboratory two‐roll mixing mill. Influences of the hybrid filler system (CB+NC) on various properties of NBR compound were analyzed. It was found that the addition of hybrid filler (CB+NC) over only carbon black enhances various properties. It was also found that the addition of nanoclay to the rubber matrix effectively improved key properties. Acoustics and electrical properties were modified with reduced water absorption because of layered clay platelets. The lower volume resistivity of NBR composites reflected better electrical conductivity attributed to the presence of nanoclay leading to effective filler connectivity. X‐ray diffraction and transmission electron microscopy measurements revealed that nanoclays were mostly intercalated and were uniformly dispersed. Use of calcium stearate facilitated dispersion of nanoclay in the rubber matrix which was observed through the formation of nanostructures including “nano” and “halo” units. Time temperature superposition in dynamic mechanical analysis test of the composites indicated lower mechanical loss in the frequency range of interest. The advantages accruing due to overall property enhancement, including lower water absorption, and better electrical and excellent acoustic properties of NBR composites make it suitable as underwater acoustic transparent materials for transducer encapsulation application. POLYM. COMPOS., 37:1786–1796, 2016. © 2014 Society of Plastics Engineers     

Synergistic effects of hybrid carbon nanomaterials in room‐temperature‐vulcanized silicone rubber

This work examines nanocomposites based on nanofillers and room‐temperature‐vulcanized silicone rubber. The carbon nanofillers used were conductive carbon black (CB), carbon nanotubes (CNTs) and graphene (GE). Vulcanizates for CB, GE, CNTs as the only filler and hybrid fillers using CNTs, CB and GE were prepared by solution mixing. The elastic modulus for CNT hybrid with CB at 15 phr (4.65 MPa) was higher than for CB hybrid with GE (3.13 MPa) and CNTs/CB/GE as the only filler. Similarly, the resistance for CNT hybrid with CB at 10 phr (0.41 kΩ) was lower than for CB (0.84 kΩ) at 20 phr and CNTs as the only filler. These improvements result from efficient filler networking, a synergistic effect among the carbon nanomaterials, the high aspect ratio of CNTs and the improved filler dispersion in the rubber matrix. © 2016 Society of Chemical Industry     

Influence of cenosphere filler additions on the three‐body abrasive wear behavior of glass fiber‐reinforced epoxy composites

The dry three‐body abrasive wear behavior of bi‐directional glass fabric reinforced epoxy composites with and without cenosphere filler have been studied using dry sand/rubber wheel abrasion tester. The angular silica sand particle sizes in the range 200–250 μm were used as dry and loose abrasives. The wear experiments have been conducted at two different loads viz., 22 and 32 N and different abrading distances viz. 270, 540, 810, and 1,080 m. The wear volume increases with an increase in load/abrading distance for all composites. From the experimental wear data it was observed that the abrasive wear of the composites dependent on the applied load and abrading distance. Further, the cenospheres filler inclusion in glass fiber reinforced epoxy (G‐E) composite showed poor abrasive wear performance. Scanning electron microscopy was used to study the morphology of the worn surface features of composites and to understand the mechanisms involved in the wear analysis. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Determination of silica content and its dispersion in NR‐PBR‐RR ternary blends/ nanocomposites by digital image analysis of SEM images

To study the silica content and its dispersion behavior in natural rubber (NR)‐polybutadiene rubber (PBR)‐reclaim rubber (RR)/ nanocomposites, scanning electron microscopy (SEM) images was used by image processing technique. A suitable algorithm was proposed to determine the silica percentage of the nanocomposites. Based on proposed algorithm, image analysis was carried out to present quantitative and qualitative measure of size distribution of silica (filler) agglomerates in the polymer nanocomposites. On the basis of stack based region detection algorithm, various sizes of silica particles was detected and 2D image was reconstructed through 10 different colors for 10 types of regions. This article also dealt with various aspects of the polymers such as filler‐filler interaction, agglomerate detection, and dispersion of filler agglomerates through image analysis of their SEM micrographs. POLYM. COMPOS., 38:2080–2089, 2017. © 2015 Society of Plastics Engineers     

The tribological behavior of micrometer and nanometer TiO2 particle‐filled poly(phthalazine ether sulfone ketone) composites

Micrometer and nanometer TiO₂ particle‐filled poly(phthalazine ether sulfone ketone) (PPESK) composites with various filler volume fractions from 0.5 to 7.5 vol % were prepared by heating compression molding. The friction and wear behaviors of the PPESK composites were evaluated using the block‐on‐ring test rig by sliding PPESK‐based composite blocks against a mild carbon steel ring under dry friction conditions. The wear debris and the worn surfaces of the PPESK composites filled with micrometer and nanometer TiO₂ particles were investigated by using a scanning electron microscope (SEM), while the structures of PPESK composites and wear debris were analyzed with IR spectra. Experimental results show that antiwear properties of the PPESK composites can be improved greatly by filling nanometer TiO₂ particles, and the friction coefficient decreases when the filler volume fraction is below 2.5%, but when the filler volume fraction is above 2.5% the friction coefficient increases gradually with increasing filler volume fraction. In the case of micrometer TiO₂ filler, wear rates increase with increasing filler volume fractions under identical test conditions, and the friction coefficients are less sensitive to the filler volume fraction. It was also found that the wear mechanism of micrometer TiO₂ particle‐filled PPESK is mainly severe adhesion and abrasive wear, while that of nanometer TiO₂ particle‐filled PPESK is mainly slight abrasive wear. In the former case, there are no transfer film formed on the surface of the counterpart steel, and wear debris are in the form of long and large ribbon. While in the latter case, the wear debris was granule and their size was about 10 μm. In case of 1 vol % nanometer TiO₂ particle‐filled PPESK composites, the transfer film was fairly thinner and smoother, and the transfer film provided better coverage on the surface of steel ring, while that of 7.5 vol % was thicker and discrete. These account for the different friction and wear behavior of micrometer and nanometer TiO₂ particle‐filled PPESK composite. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 906–914, 2004     

Dynamic properties of star‐shaped,solution‐polymerized styrene–butadiene rubber and its cocoagulated rubber‐filled with silica/carbon black

The dynamic properties, including the dynamic mechanical properties, flex fatigue properties, dynamic compression properties, and rolling loss properties, of star‐shaped solution‐polymerized styrene–butadiene rubber (SSBR) and organically modified nanosilica powder/star‐shaped styrene–butadiene rubber cocoagulated rubber (N‐SSBR), both filled with silica/carbon black (CB), were studied. N‐SSBR was characterized by ¹H‐NMR, gel permeation chromatography, energy dispersive spectrometry, and transmission electron microscopy. The results show that the silica particles were homogeneously dispersed in the N‐SSBR matrix. In addition, the N‐SSBR/SiO₂/CB–rubber compounds' high bound rubber contents implied good filler–polymer interactions. Compared with SSBR filled with silica/CB, the N‐SSBR filled with these fillers exhibited better flex fatigue resistance and a lower Payne effect, internal friction loss, compression permanent set, compression heat buildup, and power loss. The nanocomposites with excellent flex fatigue resistance showed several characteristics of branched, thick, rough, homogeneously distributed cross‐sectional cracks, tortuous flex crack paths, few stress concentration points, and obscure interfaces with the matrix. Accordingly, N‐SSBR would be an ideal matrix for applications in the tread of green tires. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40348.     

Sequences of fracture toughness micromechanisms in PP/CaCO3 nanocomposites

Mechanical properties and fracture toughness micromechanisms of copolypropylene filled with different amount of nanometric CaCO₃ (5–15 wt %) were studied. J‐integral fracture toughness was incorporated to measure the effect of incorporation of nanoparticle into PP matrix. Crack‐tip damage zones and fracture surfaces were studied to investigate the effect of nanofiller content on fracture toughness micromechanisms. It was found that nanofiller acted as a nucleating agent and decreased the spherulite size of polypropylene significantly. J‐integral fracture toughness (J_c) of nanocomposites was improved dramatically. The J_c value increased up to approximately two times that of pure PP at 5 wt % of nano‐CaCO₃. The fracture micromechanisms varied from rubber particles cavitation and shear yielding in pure PP to simultaneous existence of rubber particles cavitation, shear yielding, filler particles debonding, and crazing in PP/CaCO₃ nanocomposites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Studies of nanocomposites based on carbon nanomaterials and RTV silicone rubber

The mechanical and electrical properties were investigated for nanocomposites based on carbon nanotubes (CNTs) and conductive carbon black (CB). Solution room‐temperature‐vulcanized silicone rubber was used as a matrix. Vulcanizates based on CNTs and CB was prepared by solution mixing. With the addition of 2 phr of CNTs to the rubber matrix, the Young's modulus increased by 272% and reached as high as ～706% at 8 phr, whereas the modulus increased only 125% for CB specimens at 10 phr. Similarly, the electrical properties at 5 phr content of CNT were ～0.7 kΩ against ～0.9 kΩ at 20 phr CB. The Kraus plot from equilibrium swelling tests shows that the high properties for CNT specimens are due to high polymer–filler interfacial interactions, the small particle size that improves the distribution of the filler in a highly exfoliated state, and high electrical connective networks among the filler particles. These improvements can especially influence medical products such as feeding tubes, seals and gaskets, catheters, respiratory masks and artificial muscles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44407.     

Reinforcement of maleated natural rubber by precipitated silica

Graft copolymers of maleic anhydride and natural rubber or so‐called maleated natural rubbers (MNRs) were prepared in a molten state with varying maleic anhydride contents from 4 to 10 phr. In this work, the filler–filler and filler–rubber interactions of the MNR and precipitated silica were investigated. The MNR compounds containing 40 phr of silica both with and without 9 wt % of silane coupling agent were prepared. By increasing the maleic anhydride contents, the Mooney viscosity and cure times were increased, but the torque differences and cure rate indices were decreased. Bound rubber was increased with increasing maleic anhydride content, indicating an increase of filler–rubber interaction. In case of the compounds without silane, the MNR with 6 phr of maleic anhydride showed the lowest filler–filler interaction as indicated by a decrease of storage modulus upon an increase of strain in the filled compound i.e., Payne effect. This MNR compound also yielded the optimum mechanical properties. It has been demonstrated that a use of MNR with appropriate maleic anhydride content can reduce filler–filler interaction dramatically and hence improve a silica dispersion, as confirmed by SEM micrographs, resulting in an enhancement of the mechanical and dynamical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synergistic effect of carbon black and carbon–silica dual phase filler in natural rubber matrix

In this article, the synergistic effects of carbon black (CB) and modified carbon–silica dual phase filler (MCSDPF) on the properties of natural rubber (NR) were investigated. MCSDPF was prepared by modifying carbon–silica dual phase filler (CSDPF) with bis(3‐triethoxysilylpropyl)tetrasulphane (Si‐69). Fourier transform infrared spectroscopy and thermogravimetric analyzer analyses revealed that Si‐69 was successfully grafted to CSDPF. NR‐based compounds containing various combinations of MCSDPF and CB were prepared through a mechanical mixing. Investigations of mechanical properties, ageing resistance, abrasion resistance, dynamic mechanical properties, and morphology of tear fractured surface of MCSDPF/CB/NR vulcanizates were conducted. Our study shows that adding MCSDPF led to significant improvement in the tear resistance, fatigue life, and elongation at break of MCSDPF/CB/NR vulcanizates. Optimum stoichiometric combination of MCSDPF and CB inside the NR matrix was derived (ratio of MCSDPF and CB in wt% = 15/50), which showed synergistic effects of MCSDPF upon CB that was ultimately reflected in their tensile strength, wet skid resistance, and rolling resistance. POLYM. COMPOS., 35:1466–1472, 2014. © 2013 Society of Plastics Engineers     

Dynamic mechanical properties of styrene‐butadiene composites reinforced by defatted soy flour and carbon black co‐filler

Carboxylated styrene‐butadiene (SB) composites reinforced by a mixture of defatted soy flour (DSF) and carbon black (CB) were investigated in terms of their dynamic mechanical properties. DSF is an abundant renewable commodity and has a lower cost than CB. DSF contains soy protein, carbohydrate, and whey. Aqueous dispersions of DSF and CB were first mixed and then blended with SB latex to form rubber composites using freeze‐drying and compression molding methods. At 140°C, a single filler composite reinforced by 30% DSF exhibited roughly a 230‐fold increase in the shear elastic modulus compared to the unfilled SB rubber, indicating a significant reinforcement effect by DSF. Mixtures of DSF and CB at three different ratios were investigated as co‐fillers. Temperature sweep experiments indicate the shear elastic moduli of the co‐filler composites are between that of DSF and CB composites. Strain sweep experiments were used to study the fatigue and recovery behaviors of these composites. Compared with the DSF composites, the recovery behaviors of the 30% co‐filler composites after the eight consecutive deformation cycles of dynamic strain were improved and similar to that of 30% CB composite. Strain sweep experiments also indicated that the co‐filler composites have a greater elastic modulus than the CB reinforced composites within the strain range measured. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Studies on fly‐ash‐filled natural rubber modified with cardanol derivatives: Processability,mechanical properties,fracture morphology,and thermal decomposition characteristics

Fly ash, a by‐product of thermal power stations, was used as a filler in natural rubber (NR) in presence of 5–10 phr of phosphorylated cardanol prepolymer (PCP) and hexamethylene tetramine cured PCP (PCPHM). The compositions modified with the cardanol‐based resins showed lower power consumption for mixing, lower cure time, improved tensile properties and tear strength, and higher thermal stability. Scanning electron microscopy of the fracture surfaces of the tensile‐failed specimens showed finer and more uniformly distributed filler particles in the rubber matrix in the presence of PCP/PCPHM. The cardanol‐based resins are expected to function as a coupling agent between the filler and rubber leading to the improvement in mechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4801–4808, 2006