ESCA characterization of commercial carbon blacks and of carbon blacks from vacuum pyrolysis of used tires

Pyrolytic carbon blacks (CB_p) were obtained by vacuum pyrolysis of used tires in a batch reactor at a total pressure ranging from 0.3 to 20.0 kPa, and temperatures ranging from 420 to 700°C. CB_p differ from commercial carbon blacks used initially in the tire fabrication. A series of commercial carbon blacks with different surface areas and structures and CB_p obtained under different pyrolysis conditions were characterized using ESCA and SEM techniques to investigate the effect of the pyrolysis conditions on the chemical nature of the surface of CB_p.     

裂解炭黑在叉车轮胎胎面胶中的应用

研究裂解炭黑(CBp)在叉车轮胎胎面胶中的应用。结果表明:在胎面胶中以CBp等量替代炭黑N550,胶料的门尼粘度减小,使用20份CBp的胶料门尼焦烧时间相当,硫化胶的定伸应力和拉伸强度减小,拉断伸长率和撕裂强度增大,炭黑分散性下降;改性CBp硫化胶的耐磨性能优于CBp硫化胶。使用CBp等量替代炭黑N550可显著降低生产成本。     

Evaluation of two different scrap tires as hydrocarbon source by pyrolysis

The main objective of the present study is to investigate the effect of the polymer types in scrap tires on the pyrolysis products. Two different types of scrap tires (passenger car tire, PCT and truck tire, TT) have been pyrolyzed in a fixed bed reactor at the temperatures of 550, 650 and 800 °C under N₂ atmosphere. Pyrolysis products (gas, oil and carbon black) obtained from PCT and TT were investigated comparatively. The gaseous products were analyzed by GC–TCD. The psychical and chemical properties of pyrolytic oils were characterized by means of GC–FID, GC–MS, ¹H NMR. In addition, boiling point distributions of hydrocarbons in pyrolytic oils were determined by using simulated distillation curves in comparison with commercial diesel fuel. The production of activated carbon from pyrolytic carbon blacks (CBp) was also carried out. The composition of gaseous products from pyrolysis of PCT and TT were similar and they contained mainly hydrocarbons (C₁–C₄). Pyrolytic oils were found lighter than diesel but heavier than naphtha. The physical properties of pyrolytic oils from PCT and TT were similar at the same temperature. However, the composition of aromatic and sulphur content from pyrolysis of PCT was higher than that of TT. Furthermore, TT derived pyrolytic carbon black was found more suitable for the production of activated carbon due to its low ash content.     

Pyrolysis of scrap tyres

Cross-section samples (2–3 cm wide), representative of a whole car tyre, have been pyrolysed under nitrogen in a 3.5 dm³ autoclave at 300°C, 400°C, 500°C, 600°C and 700°C. The whole solid, liquid and gaseous products generated during each pyrolysis were collected and characterised. No significant influence of temperature on the amount and characteristics of pyrolysis products was observed over 500°C. Tyre-pyrolysis liquids are a complex mixture of C₅–C₂₀ organic compounds, with a great proportion of aromatics. They have high gross calorific values, GCV (∼42 MJ kg⁻¹) and N and S contents (0.4% and 1.2%, respectively) within those specified for certain heating fuels. About 30 wt.% of such liquids is an easily distillable fraction with boiling points (70–210°C) in the range of commercial petrol, and about 60 wt.% of them have the boiling point range (150–370°C) typical of diesel oil. Pyrolysis gases are composed of hydrocarbons of which C₁ and C₄ are predominant, together with some CO, CO₂ and SH₂; they have very high gross calorific values (68–84 MJ m⁻³). Tyre-pyrolysis residues have equal dimensions as the original tyre portion and are easily disintegrable into black powder and steel cords. The black powder has surface areas comparable to those of commercial carbon blacks, but it has a great proportion of ash and impurities (∼12 wt.%), which are the inorganic fillers added to tyre rubber; it may have a potential use as semireinforcing or nonreinforcing carbon black.     

Secondary coking and cracking of shale oil vapours from pyrolysis or hydropyrolysis of a Kentucky Cleveland oil shale in a two-stage reactor

It is widely recognized that secondary reactions which are mainly associated with minerals during oil shale retorting have a marked influence on the product yields and compositions. To understand these phenomena more clearly, the secondary reactions of shale oil vapours from the pyrolysis (or hydropyrolysis) of Kentucky Cleveland oil shale were examined in a two-stage, fixed-bed reactor in flowing nitrogen or hydrogen at pressures of 0.1–15 MPa. The vapours from pyrolysis (first stage) were passed through a second stage containing combusted shale, upgrading catalyst or neither. Carbon conversion to volatile products in the first stage increased from 49% during thermal pyrolysis to 81% at 15 MPa H₂ partial pressure. During thermal pyrolysis, total pressure had only a slight effect on carbon removal from the raw shale and subsequent deposition on to the porous solids in the second stage. Carbon deposition on to the combusted shale in the second stage was reduced to zero at 15 MPa H₂ partial pressure. The n-alkane distributions of the oils as determined by gas chromatography clearly demonstrated that higher hydrogen pressure, contact with combusted shale, or both contributed to lower-molecular-weight products.     

废旧轮胎裂解炭黑的改性及其应用进展

废旧轮胎作为对环境有害的固体废弃物，其组成包括炭黑、白炭黑和胶粉等多种有价值的资源。在现有回收技术中，废轮胎热裂解技术可有效回收裂解油、炭黑和钢丝等，在国内获得了广泛应用。相对于已经普遍利用的热解油和钢丝来说，热解炭黑含有质量分数14-21%的灰分和胶质层，它的高价值利用是实现废旧轮胎循环回用的关键。很多研究者开展了热解炭黑不同的改性处理工艺研究，改性后的热解炭黑可被应用于多个领域。该文主要概括了热解改性炭黑在橡胶生产中的补强作用、改性活性炭吸附剂、电池材料、以及沥青和油墨填料等方面的应用，综述了上述应用领域内热解炭黑的处理和改性方法，并指出今后热解炭黑高价值回用的方向和改性方法。     

Acid-base method for the demineralization of pyrolytic carbon black

The carbon black material used as reinforcing filler in tires was recovered by vacuum pyrolysis at a temperature of 500°C and a total pressure of 20 kPa. The pyrolytic carbon black obtained (CBp) was contamined by various additives of the original tire. Contaminants were also produced by chemical reactions occurring in the pyrolysis reactor. The contamination is reflected by the high content of ash and gritty materials (coke) present in the CBp. A characterization of the recovered carbon black was performed and a possible reduction of the ash content by sulfuric acid and sodium hydroxide treatment was investigated. The variables which were studied included the ratio of reactant to carbon black, the reactant concentration, the treatment temperature and the reaction time. Properties of the commercial carbon black filler grade N539 were compared to those of the CBp recovered before and after the demineralization treatment.     

液体聚异戊二烯对天然橡胶/聚丁二烯橡胶硫化胶微观结构和性能的影响

研究了液体聚异戊二烯(LIR)作为增塑剂对天然橡胶(NR)/聚丁二烯橡胶(BR)硫化胶微观结构、弯曲疲劳性能、压缩疲劳性能和动态力学性能的影响,并与加入工业用增塑剂芳烃油的硫化胶进行了对比。结果表明,加入LIR较芳烃油有利于炭黑在NR/BR体系中的分散;随着LIR用量的增加,NR/BR硫化胶的耐屈挠疲劳性能基本不变;与芳烃油增塑的NR/BR体系相比,LIR增塑NR/BR体系的耐屈挠疲劳性能较优,压缩疲劳生热和压缩永久变形较低;加入LIR降低了硫化胶滚动阻力的同时减弱了其抗湿滑性。     

Pyrolysis of polypropylene in the presence of oxygen

The polypropylene (PP) was coated on porous α-alumina particles and then pyrolyzed in a flow of helium or a mixture of helium–oxygen at atmospheric pressure. The mass release from PP was dramatically enhanced in the presence of oxygen at temperatures in the range of 200–300°C. The temperature for the 50% mass release was ca. 250°C at an oxygen partial pressure (P_O2) of 16.7 kPa and was lowered by 190°C as compared with a system which contained no oxygen. When P_O2 was higher than 4.2 kPa, the mass release rate obeyed first-order kinetics with respect toP_O2, and the activation energy was calculated and found to be 65–75 kJ/mol. The activation energy was considerably lower than that for pyrolysis in the absence of oxygen (230 kJ/mol) and agreed well with the value for formation of peroxides on tertiary carbons. When the pyrolysis was conducted at 250°C under P_O2=16.7 kPa, the carbon-based yield of volatiles exceeded 90%, and the yields of CS₂-soluble oil and wax were 76% and 6.0%, respectively. The carbon-based yields of other products were: Acetone, 2.5%; methanol, 1.5%; CO, 3.0%; CO₂, 2.2% and solid residue; 10%. Proton NMR (nuclear magnetic resonance) analysis showed that the CS₂-soluble oil possessed an elemental composition of C₁₀₀H₁₈₇O₁₁. The average number of carbon atoms per molecule of the oil was approximately 10, and –CH₂–OH, –C(CH₃)CO and CH₂ were typical end groups. Their formation is explained by the decomposition of peroxides formed on tertiary carbons.     

Experimental Study on Pyrolysis of Black Non-Charring Polymers in the Reduced-Pressure Environment

A series of experiments on a black non-charring polymer in the low-pressure chamber is conducted under different external heat fluxes. The surface and bottom temperatures and the mass loss of the sample are measured. A parameter T _p is introduced to describe the impact of pressure on the surface temperature. There is a loose layer of the char residue left with significant pyrolysis bubbles under the low heat flux, and the bubble size decreases with pressure. The parameter T _p is found to exhibit a significant decline trend with increasing pressure, and the mass loss rate of the sample decreases apparently as the pressure increases. However, under a high heat flux, the char residue is denser, and the pyrolysis bubbles are not observed. The value of T _p and the mass loss rate of the sample have no obvious relationship with pressure. The average pyrolysis rate is linearly proportional to p ^a .     

Fe/N/C non-precious catalysts for PEM fuel cells: Influence of the structural parameters of pristine commercial carbon blacks on their activity for oxygen reduction

Fifteen commercial SRCC furnace carbon blacks of various grades, ranging from N1 to N9, were used as carbon supports in the preparation of Fe/N/C type electrocatalysts for the oxygen reduction reaction (ORR) in PEM fuel cell conditions. All catalysts were prepared by loading the various carbon grades with 0.2 wt.% Fe as iron acetate and heat-treating the resulting material at 950 °C in pure NH₃. This reaction provides the nitrogen content and the microporosity necessary to synthesize and host the Fe/N/C catalytic sites that perform ORR. The maximum catalytic activity (V_pr max) for each carbon grade was determined by optimizing pyrolysis time. The aim of this study is to determine which structural characteristics of the pristine carbon black are important for maximizing catalytic activity. Three structural parameters that influenced the catalytic site density on the carbon support were identified. They are: (i) the average particle diameter of the pristine carbon black, d_particle, available from BET area measurements; (ii) the amount of disordered phase which is proportional to W_D, the width at half maximum of the D peak in the Raman spectrum of the pristine carbon; and (iii) the mean size of the graphene layers characterizing the graphitic crystallites in the carbon black, L_a. The latter is available by Rietveld analysis of the XRD spectra of the pristine carbons. The best catalytic activities are obtained for the smallest d_particle, the largest W_D, and the largest L_a. Optimizing these three parameters maximizes the fraction of the pristine carbon black that becomes microporous upon reaction with NH₃ and, therefore, enables the formation of Fe/N/C catalytic sites. A FeN₂₊₂/C structure bridging two adjacent graphitic crystallites is proposed as a potential model for most of the catalytic sites present in such Fe/N/C type catalysts.     

Transformation of vulcanized natural rubber into lower molecular weight polymers and their application to grafted copolymer synthesis with some vinyl monomers

Graft copolymerization of several vinyl monomers onto polyisoprene was carried out to explore the possibility to recycle waste rubber to useful functional materials. Synthetic polyisoprene, vulcanized natural rubber, and vulcanized natural rubber with carbon black were converted to lower molecular weight polymers at 300°C, under air or nitrogen atmosphere. The obtained low molecular weight natural rubber and polyisoprene were soluble in organic solvents, such as hexane, toluene, tetrahydrofuran (THF), chloroform, and monochlorobenzene. Radical copolymerization of styrene with a thermally fragmented natural rubber was carried out at 80°C in bulk for 2 h in the presence of 2,2′‐azobis(isobutyronitrile) (AIBN) under air atmosphere to give the corresponding grafted copolymer. The obtained polymer was a beige powdery copolymer at room temperature and consisted of isoprene (38 mol %) and styrene (62 mol %) units, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4003–4010, 2006     

Influence of γ-irradiation on proton spin–lattice relaxation of SBR used as antirads and its ESR investigation

Proton spin–lattice relaxation time t₁ was measured on SBR samples with carbon black or kaolin filler using modified linseed oil. The NMR pulse technique at 90MHz was used in the temperature range from 180 to 400 K. The temperature dependence of t₁ indicates that samples filled with carbon black have similar molecular dynamics to the standard unfilled SBR samples. The activation energy for the motion of the main chain for these samples amounts to 16.4kJ/mol. Samples containing linseed oil modified with para-toluidine showed an activation energy of about 14.6kJ/mol and were not affected by γ-irradiation. Values of the minimum relaxation time t^min₁ were increased by γ-irradiation in comparison with a standard SBR sample. ESR measurements carried out at room temperature by means of an X-band spectrometer indicated that unidentified radicals within the rubber were formed during its mastication with vulcanizing additives. The ESR spectra did not change during the vulcanization process. Samples filled with carbon black showed a broadening of the ESR line; this is consistent with the increase in the electrical conductivity.     

Filler-elastomer interactions: influence of oxygen plasma treatment on surface and mechanical properties of carbon black/rubber composites

In this work, the influence of oxygen plasma treatment on the surface and adsorption properties of carbon blacks was investigated using X-ray photoelectron spectroscopy (XPS), ζ-potential, and BET isotherms. Then the mechanical properties [tensile strength and tearing energy (G_IIIC)] of carbon black/acrylonitrile butadiene rubber (NBR) composites were measured. As a result, it was found that oxygen plasma treatment generated oxygen-containing functional groups, such as, carboxyl, hydroxyl, lactone, and carbonyl groups, on the carbon black surfaces, resulting in a decrease in the equilibrium spreading pressure or London dispersive component of surface free energy. The tearing energy of the carbon black/NBR composites improved as the oxygen-containing functional groups on the carbon black surfaces increased. This revealed that there is a relatively high degree of interaction between the polar NBR and the oxygen-functional groups of carbon blacks.     

废轮胎裂解炭黑的深加工及应用研究

以废轮胎裂解炭黑为原料,经粉碎分级、表面改性等系统工艺条件,制备出性能优良的超细改性裂解炭黑。经天然橡胶的应用实验证实,超细改性裂解炭黑填充天然橡胶的性能良好,其应用前景广阔。     

Hydrogenation of synthetic cis‐1,4‐polyisoprene and natural rubber catalyzed by [Ir(COD)py(PCy3)]PF6

In the presence of chlorinated solvents, the catalytic complex [Ir(COD)py(PCy₃)]PF₆ (where COD is 1,5‐cyclooctadiene and py is pyridine) was an active catalyst for the hydrogenation of synthetic cis‐1,4‐polyisoprene and natural rubber. Detailed kinetic and mechanistic studies for homogeneous hydrogenation were carried out through the monitoring of the amount of hydrogen consumed during the reaction. The final degree of olefin conversion, measured with a computer‐controlled gas‐uptake apparatus, was confirmed by Fourier transform infrared spectroscopy and ¹H‐NMR spectroscopy. Synthetic cis‐1,4‐polyisoprene was used as a model polymer for natural rubber without impurities to study the influence of the catalyst loading, polymer concentration, hydrogen pressure, and reaction temperature with a statistical design framework. The kinetic results for the hydrogenation of both synthetic cis‐1,4‐polyisoprene and natural rubber indicated that the hydrogenation rate exhibited a first‐order dependence on the catalyst concentration and hydrogen pressure. Because of impurities inside the natural rubber, the hydrogenation of natural rubber showed an inverse behavior dependence on the rubber concentration, whereas the hydrogenation rate of synthetic rubber, that is, cis‐1,4‐polyisoprene, remained constant when the rubber concentration increased. The hydrogenation rate was also dependent on the reaction temperature. The apparent activation energies for the hydrogenation of synthetic cis‐1,4‐polyisoprene and natural rubber were evaluated to be 79.8 and 75.6 kJ/mol, respectively. The mechanistic aspects of these catalytic processes were discussed on the basis of observed kinetic results. The addition of some acids showed an effect on the hydrogenation rate of both rubbers. The thermal properties of hydrogenated rubber samples were determined and indicated that hydrogenation increased the thermal stability of the hydrogenated rubber but did not affect the inherent glass‐transition temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4219–4233, 2006     

Molecular dynamics simulation of diffusion behavior of cyclohexane in natural rubber during reclamation

Reclaiming oil is a common additive involved in many physical rubber reclamation processes. In this work, molecular dynamics simulation is used to investigate the diffusion of oil in natural rubber (NR) under different temperatures and pressures. The structures of polyisoprene and cyclohexane molecules are constructed. The diffusion coefficients (Ds) of cyclohexane molecules in polyisoprene under different temperatures and pressures are calculated. The free volumes are also obtained to better understand the change in microstructure. The diffusion experiments of oil in NR samples under different temperatures and pressures are also conducted. The simulation results show that D increases as the temperature rises, especially at temperatures above 400 K, while the pressure does not affect D significantly. The fractional free volume calculated from the free volume and occupied volume exhibits a similar trend to that of D. Furthermore, the calculated Ds agree well with the experimental results. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40347.     

Composition dependence of dielectric properties,elastic modulus,and electroactivity in (carbon black‐BaTiO3)/silicone rubber nanocomposites

The dielectric properties, elastic modulus, and electromechanical responses of dielectric elastomers (DEs) consisting of silicone rubber and carbon black (CB) incorporated with BaTiO₃ (BT) were studied. When compared with single filler/rubber composites, the resulting three‐component nanocomposites yielded very abnormal phenomena. They might be attributed to the interactions between the two kinds of fillers. The increase in concentration of CB (BT) would play a destructive role to the network structure formed by BT (CB) particles. The maximum electromechanical strain of the nanocomposites achieved at mass fraction m_CB = 0.03 and m_BT = 0.06. The resultant electromechanical strain would be attributed to the large dielectric permittivity in the three‐component nanocomposites, in which the BT particles themselves have a high dielectric permittivity and the electrical networks of CB particles have a contribution on the increase in dielectric permittivity of the three‐component nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Unlubricated rolling and sliding wear against steel of carbon‐black‐reinforced and in situ cured polyurethane containing ethylene/propylene/diene rubber compounds

The dry rolling and sliding friction and wear of ethylene/propylene/diene rubber containing carbon black and in situ cured polyurethane (EPDM+PUR_CB) were studied. For rolling and sliding tests against steel counterparts, different experimental conditions and tribotests were selected. The apparent network properties and phase structures of the rubbers were derived from dynamic mechanical thermal analysis and atomic force microscopy results. It was concluded that in EPDM+PUR_CB, both rubber phases, present in a 1 : 1 ratio, were continuous (interpenetrating network). The coefficient of friction (COF), specific wear rate (W_s), and heat development during the tribotests were determined. The carbon black and polyurethane contents did not much influence the COF in rolling wear tests. W_s of the ethylene/propylene/diene rubber containing carbon black went through a minimum as a function of the carbon black content. W_s of the EPDM+PUR_CB compounds decreased monotonously with an increasing amount of carbon black. The incorporation of polyurethane into the ethylene/propylene/diene rubber compounds decreased the resistance to rolling wear markedly. With carbon black filling of the ethylene/propylene/diene rubber–polyurethane compound, the COF and W_s increased and dramatically decreased, respectively, under sliding wear. The wear mechanisms were inspected with scanning electron microscopy and discussed as a function of recipe modifications and changes in the testing conditions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Studies on the structure and formation mechanism of carbon gel in the carbon black filled polyisoprene rubber composite

The structure and formation mechanism of carbon gel in carbon black filled polyisoprene composites were studied by the pulsed NMR technique. The composites were prepared from a wide range of molecular weights by a solution blend. The carbon gels were extracted from the composites by a solvent-extraction method. The content of carbon gel was not governed by the molecular weight of rubber but was controlled by the viscosity of rubber solutions which were used for the blend. Three rubber phases, having different spin-spin relaxation times, were detected in all the carbon gels. The increase of carbon gel content in the composites was mainly from the increase of highly mobile rubber phase, and the gel became soft with the development of this phase. On the other hand, the content and structure of glassy rubber phases were not affected by the size of the carbon gel, and they showed almost a constant value despite the large change in the carbon gel content. A part of the highly mobile rubber phase in the gels could be removed by solvent extraction at high temperature. These results suggest that the formation of carbon gel is primarily governed by two factors: One is the well-known rubber-carbon black interaction, and the other is a physical crosslink between the carbon gel and unbound rubber molecules during blend. © 1996 John Wiley & Sons, Inc.