Influence of carbon black on uncompatibilised and compatibilised SBR–NBR blends

Abstract

Elastomeric blends based on SBR and NBR have been prepared, giving emphasis to differences in blend composition. It was observed from dynamic mechanical analysis that the SBR–NBR blends can be compatibilised by addition of 5 pphr dichlorocarbene modified styrene/butadiene rubber. The efficiency of carbon black in uncompatibilised and compatibilised blends was evaluated with reference to their processing characteristics and technological properties and the resistance of the vulcanisates towards thermal and oil aging was analysed. The changes in technological properties have been correlated with variations in crosslink density estimated from stress–strain and swelling behaviour. The swelling studies are also extended to evaluate the reinforcing nature of the filler. The results of the study reveal that compatibilised blends show enhanced mechanical properties in the presence of HAF carbon black in comparison with uncompatibilised samples.     

Changes in morphology and properties of NR–NBR blends. Effect of viscosity ratio modified by liquid natural rubber and epoxidised liquid natural rubber

Abstract

Changes in rheological properties, morphology, and oil resistance in NR–NBR blends by viscosity ratio have been investigated. In this study, the viscosity ratio was modified by mechanical mastication and addition of liquid natural rubber (LNR) and epoxidised liquid natural rubber (ELNR). The results reveal that as viscosity ratio increased from 0·5 to 1·0, Mooney viscosity of the blends increased, and then decreased sharply as the viscosity ratio further increased from 1·0 to 2·0. The addition of LNR and ELNR for plasticising NR and NBR, respectively, does not significantly affect cure properties of the blends. The phase size of the NR dispersed phase depends strongly on the viscosity ratio. The high viscosity of the matrix and/or the low viscosity of the dispersed phase promote breaking up of the dispersed phase. Unexpectedly, a decrease in size of the dispersed phase by the modification of viscosity ratio via the use of low molecular weight rubber (i.e. LNR and ELNR) did not result in an improvement in oil resistance.     

Steam reforming of methanol over Pt–Zn alloy catalyst supported on carbon black

Steam reforming of methanol over Zn-promoted Pt catalyst supported on an electrically conductive carbon black has been investigated after H₂ reduction at 873 K. X-ray diffraction measurement showed that Pt–Zn alloy was formed on the carbon black (C). The Zn-promoted Pt/C catalyst showed higher activity and selectivity to CO₂ compared with unpromoted Pt/C catalyst. Methyl formate was formed over the Zn-promoted Pt/C catalyst in decomposition of methanol (without water). This suggests that steam reforming of methanol over the Zn-promoted Pt/C catalyst can proceed via methyl formate, which is different from that of the unpromoted Pt/C catalyst.     

Compatibilisation of polypropylene–polystyrene blends: Part 1 – Effect of mixing intensity on morphology andrheological properties

Abstract

Propylene copolymer blends have been prepared using a proprietary, in reactor, grafting polymerisation technique, to give two phase materials composed of 70% polypropylene, 20% polystyrene, and 10%polypropylene- graft-polystyrene (PP-g-PS). The present study was carried out to determine the efficiency of PP-g-PS relative to block-copoly(styrene/ethylene–butylene/ styrene) (SEBS) as a compatibiliser for polypropylene–polystyrene blends by measuring rheological properties and examining the morphological structure. Mixing experiments were conducted on a twin screw mixing element evaluator and on a commercial ZSK-30 extruder. Dynamic mechanical analysis was used to characterise the viscoelastic properties of the extruded polymer pellets and transmission electron microscopy was used to examine the morphology of the polymer throughout its processing history, i.e. from carcasses at different stages of the mixing operations to injection moulded specimens. Both the graft copolymer, PP-g-PS, and the black terpolymer, SEBS, were found to enhance the compatibilisation of the blends, but the graft copolymer was found to be more effective. The results also show that the intensity of mixing affects the molecular and morphological structures of the graft and graft–rubber blends, as indicated by the intrinsic viscosity values of the extracted isotactic polypropylene fraction of the blends. This is supported by morphological examination of the graft blend, which showed a phase inversion from co-continuous to dispersed phase morphology during extrusion.     

The effect of antioxidants on the oxidation behaviour of magnesia–carbon refractory bricks

Oxidation of carbon is the main problem in magnesia–carbon refractories. The effects of various antioxidants, Al, Si, SiC and B₄C on the oxidation resistance of magnesia–carbon bricks were investigated at temperatures of 1300 °C and 1500 °C. Carbon losses as wt.% of the bricks were calculated and oxidized areas of the bricks were examined by XRD, SEM and EDS. B₄C was found to be the most effective antioxidant at both temperatures. Magnesium–borate (Mg₃B₂O₆) compound was determined to be present by characterization studies on B₄C added specimens. Magnesium–borate, which is in liquid state above 1360 °C, had an excellent effect on the oxidation resistance of the bricks by filling up the open pores and forming a protective layer on the surface. Forsterite (Mg₂SiO₄) and spinel (MgAl₂O₄) provided similar effects on the Si and Al added specimens respectively at both temperatures. The SiC added specimens had similar phases with Si added specimens, but SiC was the least effective antioxidant at both temperatures.     

Elastomeric conductive composites based on conducting polymer–modified carbon black

Thermally stable elastomeric composites were prepared via melt processing from poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS) and conducting polymer-modified carbon black (CPMCB) additives. CPMCB additives represent a novel thermally stable conductive compound made via “in-situ” deposition of polyaniline or polypyrrole on carbon black particles. Incorporating CPMCB is advantageous to the melt processing of composites, as it reduces the melt viscosity in comparison to the use of pure carbon black. Thermogravimetric analyses (TGA) showed that the composites are thermally stable with no appreciable degradation at temperatures as high as 300°C. In addition, the electrical conductivity of the composites was found to be very stable at high temperatures. Polym. Compos. 25:617–621, 2004. © 2004 Society of Plastics Engineers.     

The effect of catalyst and heat treatment on the properties of carbon–metal composites

Carbon gel and carbon–nickel–palladium doped gels (C–Ni–Pd) were prepared by carbonising resorcinol–formaldehyde (RF) hydrogel and resorcinol–formaldehyde–nickel–palladium (RF–Ni–Pd) hydrogels at 900 °C in a nitrogen atmosphere. RF and RF–Ni–Pd hydrogels were synthesized through sol–gel polycondensation followed by ambient drying. The aim of this study was the determination of the effect of heat treatment in air at 450 °C on the properties of C–Ni–Pd gels prepared using different Pd salts. In the present work, Ni was added as acetate whereas Pd was added as acetate (CA–Ni–Pd) and as chloride (CB–Ni–Pd). Samples were examined by scanning electron microscopy and X-ray diffraction. Surface area was characterized by N₂ adsorption at ?195.5 °C. Thermogravimetric analysis was carried out in order to determine the thermal characteristics of carbon gel and nickel–palladium composites in air atmosphere. CA–Ni–Pd composite had a higher activity and two-phase reaction compared to the CB–Ni–Pd composite. Further improvement of the electrolyte diffusion into the particles of nickel and palladium was obtained by oxidative thermal treatment. During this process a structural modification of the material took place, consequently leading to changes in the electrochemical properties of the composites.     

The effect of metal–solvent properties on the alteration of specific zones on a carbon phase diagram

In this work Fe–Sb and Fe–Ge alloys (up to 10 wt.% Sb, Ge) were used as a solvent-catalyst for diamond synthesis at pressures of 5–6 GPa and temperatures of 1800–1900 K. Carbon solubility, capillary properties and synthesis performance of alloys were investigated. When using alloys with additive content up to 10 wt.%, rapid graphite to diamond transformation was observed. In spite of identical P,T-conditions and identical composition of a solvent–catalyst, different crystal morphology on the top and on the bottom sides of a diamond polycrystalline layer was formed, although their habit type {111} was identical. Thermodynamic and kinetic aspects of these phenomena are discussed.     

Studies on the adhesive properties of neoprene–phenolic blends

Polychloroprene (neoprene) rubber in combination with phenolic resins is a versatile adhesive formulation. The phenolic resin used in this case was derived from a mixture of cardanol, a meta-substituted naturally-occurring substance, and phenol. Cardanol is the main ingredient of cashew nut shell liquid (CNSL), a renewable resource. This study aims to investigate the adhesive properties of cardanol-based resin when used in combination with two grades of polychloroprene rubber. The effects of varying the solid content and resin content, choice of resin, fillers, crosslinking agents, adhesion promoters, solvents, etc. in the adhesive formulations were also studied. Moreover, relative proportions of rubber and resin that give optimum adhesion performance were identified. The results show that cardanol-phenol-formaldehyde resin is an effective ingredient in adhesives for bonding aluminium to aluminium and SBR to SBR. The addition of 3-aminopropyltriethoxysilane to the formulation improves the bond strength of metal-to-metal specimens.     

Conductive rubbers made by adding conductive carbon black to EVA,EPDM, and EVA–EPDM blends

Abstract

Electrically conductive rubbers have been prepared by the incorporation of conductive carbon black into ethylene/vinyl acetate (EVA) copolymers, ethylene/propylene/diene monomer (EPDM) terpolymers, and a 50 : 50 EVA–EPDM blend. The electrical and mechanical properties of these composites have been studied. The percolation limit for high conductivity in the filled rubbers depends on their compatibility as well as the viscosity and polarity of the rubbers. The electrical resistivity decreases with increasing temperature and the activation energy for conduction decreases with increasing filler loading. The temperature dependence of resistivity can be correlated with data from DSC, XRD, and DMTA measurements. Electrical set and electrical hysteresis have been observed during heating–cooling cycles. The change in resistivity with applied pressure is also reported.     

Effect of carbon black on corrosion resistance of Al2O3–SiC–C castables to SiO2–MgO slag

Metallurgical solid waste recycling is the shape of things to come in green development of Chinese iron and steel industry. Utilization of ironworks slag for producing mineral wool at high temperature is an important approach. However, refractory lining is seriously corroded by the SiO₂–MgO based slag at 1600 °C during the production process. Different production steps need different atmospheres, the changeable service atmospheres (air and reducing atmosphere) put forward high requirements for slag resistance. The Al₂O₃–SiC–C castables containing carbon black are usually used in iron runner, which faces high-temperature service condition of 1450 °C–1500 °C. Nevertheless, the function of carbon black in the Al₂O₃–SiC–C castables at 1600 °C is till essentially unknown. In the current study, the carbon black was introduced to tabular alumina based Al₂O₃–SiC–C castables to improve corrosion resistance to SiO₂–MgO based slag at 1600 °C. The result showed that 0.4 wt% carbon black was suitable for the castables, which the slag resistance of castables was significantly improved. The carbon black had contributed to block slag by wettability resistance. By comparison with the castables without carbon black, the corrosion index and penetration index had been reduced by 20.2% and 28.0%, respectively, under air atmosphere. And there were little corrosion or penetration under reducing atmosphere for castables with 0.4 wt% carbon black. For the mechanical properties, the Al₂O₃–SiC–C castables with 0.4 wt% carbon black could serve production process although the carbon black impaired the physical properties.     

Atomistic analyses of the effect of temperature and morphology on mechanical strength of Si–C–N and Si–C–O nanocomposites

3-D molecular dynamics (MD) analyses of SiC–Si₃N₄ nanocomposite deformation and SiCO nanocomposite deformation are performed at 300 K, 900 K, and 1500 K. In SiC–Si₃N₄ nanocomposites, distribution of second phase SiC particles, volume fraction of atoms in GBs, and GB thickness play an important role in temperature dependent mechanical behavior. The deformation mechanism is a trade-off between the stress concentration caused by SiC particles and Si₃N₄–Si₃N₄ GB sliding. The temperature increase tends to work in favor of GB sliding leading to softening of structures. However, microstructural strength increases with increase in temperature when GBs are absent. In the case of SiCO nanocomposites, findings indicate that temperature change dependent amorphization of nanodomains, the nanodomain wall placement, the nanodomain wall thickness, and nanodomain size are important factors that directly affect the extent of crystallinity and the strength against mechanical deformation.     

Understanding the influence of anti-reversion agent and metal oxide dose on natural rubber–carbon black system

Sulfidic linkages that are formed during the vulcanization process of natural rubber (NR) are unstable at a higher temperature and can be reversed into conjugated diene. To overcome such issue and to build a compound that is hostile to inversion and with increasing service life, anti-reversion agent (ARA), for example, N,N′-4,4′-diphenylmethyene bismaleimide (BMDM), is added into the formulation. This work explains the conjugation reaction mechanism of conjugated diene and BMDM by means of gas chromatography–mass spectrometry and Fourier transform infrared spectroscopy. The first phase of this study is associated with the change in ARA dosage keeping ZnO dosage the same. It is observed that 5 phr of BMDM and 2 phr ZnO combination (ARA4) shows lowest reversion at 160°C. The modulus value at 300% elongation increased 12% by the incorporation of BMDM as compared to the compound of no BMDM (ARA1). The second part is all about keeping BMDM dosage the same at 5 phr level and varying ZnO phr by 3, 4, and 5. From the overall results, it is observed that at a suitable dosage of BMDM and ZnO (5 phr BMDM and 3 phr ZnO combination [ARA5]), least reversion can be achieved and vulcanizates containing optimized BMDM and ZnO show better retention properties after aerobic aging as compared to ARA1.     

Carbon black reinforced thermoplastic vulcanisates based on ethylene–vinyl acetate copolymer/styrene–butadiene rubber blends

Thermoplastic vulcanisates (TPVs) based on ethylene–vinyl acetate copolymer (EVA)/styrene–butadiene rubber (SBR) blends were prepared by dynamic vulcanisation, with the TPVs being reinforced by carbon black (CB). Experimental results indicated that the mechanical properties of dynamically vulcanised EVA/SBR blends were enhanced remarkably by the incorporation of CB. Morphology study showed that the SBR particles with average diameter of 20?μm were dispersed evenly on the etched surface of EVA/SBR/CB TPVs. The Mullins effect could be observed in the stress–strain curves of EVA/SBR TPVs and EVA/SBR/CB TPVs during the uniaxial loading–unloading cycles. Compared with EVA/SBR TPVs, CB reinforced EVA/SBR TPVs had the relatively higher stress, residual deformation and internal friction loss.     

Molecular dynamics simulations of the effect of the volume fraction on unidirectional polyimide–carbon nanotube nanocomposites

Molecular dynamics (MD) simulations were used to predict the effect of the reinforcement volume fraction on a unidirectional nanocomposite comprised of a polyimide and multi-walled carbon nanotubes (MWCNTs). We derived a modified volume fraction equation that takes the interface into account, and thus can precisely calculate the volume fraction of the reinforcement. From the MD simulations, both the stress and the modulus are predicted to increase with increasing number of MWCNTs as a function of a constantly applied strain, although some interesting observations were made in comparison to a pure polyimide system that is ordered, akin to the pre-nucleated crystalline system. In addition, we developed an approach to indirectly predict the change in the degree of order in the matrix with the addition of the CNT reinforcements. The results suggest that the degree of ordering increases with an increase in the volume fraction of MWCNTs, especially at the polymer–CNT interface according to number density plots of the polymer, which is consistent with the hypothesis that CNTs can act as nucleation sites for the crystallization of the polymer matrix.     

Elastomeric composites based on ethylene–propylene–diene monomer rubber and conducting polymer-modified carbon black

Thermally stable elastomeric composites based on ethylene–propylene–diene monomer (EPDM) and conducting polymer-modified carbon black (CPMCB) additives were produced by casting and crosslinked by compression molding. CPMCB represent a novel thermally stable conductive compound made via “in situ” deposition of intrinsically conducting polymers (ICP) such as polyaniline or polypyrrole on carbon black particles. Thermogravimetric analysis showed that the composites are thermally stable with no appreciable degradation at ca. 300°C. Incorporating CPMCB has been found to be advantageous to the processing of composites, as the presence of ICP lead to a better distribution of the filler within the rubber matrix, as confirmed by morphological analysis. These materials have a percolation threshold range of 5–10 phr depending on the formulation and electrical dc conductivity values in the range of 1 × 10⁻³ to 1 × 10⁻² S cm⁻¹ above the percolation threshold. A less pronounced reinforcing effect was observed in composites produced with ICP-modified additives in relation to those produced only with carbon black. The results obtained in this study show the feasibility of this method for producing stable, electrically conducting composites with elastomeric characteristics. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Physical–mechanical properties of carbon black–nanoclay composites of butyl rubber as curing bladder compounds

Abstract

Partial replacement of carbon black (CB) by organically modified montmorillonite (OMMT) in bladder compounds and synergistic effect between OMMT and CB on required properties were studied. X-ray diffraction results revealed intercalation of rubber into OMMT galleries. Mechanical interaction between rubber and filler, mechanical stability in oxidative aging, resistance to permanent set, reduction in permeation to CO₂, and resistance to thermal degradation were all in favour of clay containing composites, especially the compound with 45?phr CB and 4?phr OMMT.     

Impact of graphene oxide nanoparticles and carbon black on the gamma radiation sensitization of acrylonitrile–butadiene rubber seal materials

Seals prepared from acrylonitrile–butadiene rubber (NBR) are primarily used in nuclear services. Nevertheless, at relatively high ionizing radiation doses, NBR seal materials may undergo radiation-induced degradation processes, leading to adverse effects on the sealing ability life. Herein, to strengthen the functional characteristics of NBR seals against radiation, graphene oxide (GO) nanoparticles were prepared and characterized by transmission electron microscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR), and ultraviolet/visible spectroscopies. Various NBR/GO composites fabricated with different ratios of GO nanoparticles and in the presence or absence of carbon black (CB) were investigated via cross-linking density, scanning electron microscopy, XRD, FTIR, and mechanical and thermal stability analyses. The synergistic effect of the simultaneous presence of GO and CB on the NBR seal sensitization to gamma radiation up to a dose of 1 MGy was studied. The physicomechanical properties were enhanced by adding GO nanosheets up to 3 phr and by incorporating 35 phr of a CB with GO until 5 phr. Further, the application of γ-irradiation resulted in an overall enhancement in the mechanical, physical, and thermal stability of the prepared composites up to 0.5 and 1 MGy with GO nanosheets in the absence or presence of CB particles, respectively. The mechanical measurements indicated significant increments by loading with GO nanosheets in the absence and presence of CB as well as by irradiation. The tensile strength elevated up to about 121%, 336%, and 366% by adding 3 phr GO, 3 GO:35 CB phr, and 5 GO:35 CB phr, respectively.     

Properties influenced by addition of copoly (ethylene/octene) in BR–NBR blends

Abstract

The effects of copoly (ethylene/octene) (EOM) on rheological, mechanical, and cure properties and on carbon black distribution in each phase of butadiene rubber–nitrile/butadiene rubber (BR–NBR) blends have been investigated. It was found that EOM added to the blends is able to function as a plasticising agent for BR and NBR, and the plasticising efficiency of EOM is more significant in NBR than BR. With increasing EOM content, the deviation of Mooney viscosity from the additive line (interpolated values) reduces markedly. In pure components (i.e. 100 : 0 and 0 : 100), cure rate reduces and cure time increases with addition of EOM. In contrast in the blend systems, cure rate increases and cure time decreases when EOM is added. The distribution of carbon black in each phase of the blends is strongly controlled by the viscosity of each phase in the blend. The lower the phase viscosity, the greater the residual carbon black. Accordingly, dynamic mechanical thermal analysis reveals a slight shift in the glass transition temperature of the BR phase to higher temperature, compared with the NBR phase, as EOM is added. From the results obtained, it is proposed that EOM exists in the interfacial area between the two phases. However, at higher amounts of EOM, saturation of EOM at the interfacial area occurs and the excess EOM starts to migrate to the BR phase. Further increase in EOM concentration leads to saturation of EOM in the BR phase and EOM then migrates to the NBR phase.     

Encapsulated carbon black prepared by sol–gel-spraying: A new black ceramic pigment

As a new black ceramic pigment, encapsulated carbon black pigment has been prepared by a sol–gel-spraying method. The obtained pigment sintered at 900 °C for 2 h in air has a deep black hue (L* = 19), indicating carbon black can be fully covered. In the pigment, a dense coating layer on carbon black is formed due to the fast transformation from sol into gel by rapid extraction of solvent. The transparent silica phase spaces out the fine crystalline (zirconia or zircon), which permits to display the color of carbon black. This preparation method provides a way to prepare the encapsulated pigments. It will provide more colorful ceramic pigment applied in ceramic decoration by encapsulating.