Effect of polyamide 6 on the morphology and electrical conductivity of carbon black-filled polypropylene composites

Carbon black (CB)-filled polypropylene (PP) with surface resistivity between 10⁶ and 10⁹ Ω sq^-1 is the ideal antistatic plastic material in the electronics and electric industry. However, a large amount of CB may have an adverse effect on the mechanical properties and processing performance of the material, thus an improved ternary system is developed. Blends of CB-filled PP and polyamide 6 (PA6) have been prepared by melt blending in order to obtain electrically conductive polymer composites with a low electrical percolation threshold based on the concept of double percolation. The morphological developments of these composites were studied by scanning electron microscopy. The results showed that CB particles were selectively dispersed in PA6 phases due to the good interaction and interfacial adhesion between CB and PA6. At the same CB loadings, the surface resistivity of PP/PA6/CB composite was smaller than that of PP/CB composite system, which indicated the better conductivity in the former composite. The increasing amount of PA6 in the composites changed the morphology from a typical sea-island morphology to a co-continuous morphology. What is more, with 8 wt% of CB and PP/PA6 phase ratio of 70/30 in which the PP and PA6 phases formed a co-continuous structure, the electrical conductivity of the composite peaked at 2.01 × 10⁵ Ω sq^-1.

Photothermal Nanoparticle Initiation Enables Radical Polymerization and Yields Unique, Uniform Microfibers with Broad Spectrum Light

Photothermal processes are utilized across a variety of fields, from separations to medicine, and are an area of active research. Herein, the action of a solar simulator upon carbon black nanoparticles is shown to result in photothermally initiated chain-growth polymerization of methyl acrylate, butyl acrylate, and methyl methacrylate initiated by benzoyl peroxide. With use of methyl acrylate as the model system, products from this reaction are shown to be apparently indistinguishable on the molecular level, but result in unique microstructures relative to the thermal controls. The relative contribution of bands of the UV/visible spectrum to the polymerization initiation show that red/infrared wavelengths are most important for the initiation to occur. Kinetic analysis of the initiator homolysis indicate that the apparent reaction rate is accelerated in the photothermal condition.

Carbon Black-Modified Electrodes Screen-Printed onto Paper Towel, Waxed Paper and Parafilm M®

Herein, we evaluated the use of paper towel, waxed paper, and Parafilm M^® (Heathrow Scientific, Vernon Hills, IL, USA) as alternative substrates for screen-printed sensor manufacturing. Morphological study was performed to evaluate the adhesion of the ink on these uncommon substrates, as well as the morphology of the working electrode. The electrochemical characterization was carried out using ferricyanide/ferrocyanide as redox couple. To enhance the electrochemical properties of the developed sensors, the nanomaterial carbon black was used as nanomodifier. The modification by drop casting of the working electrode surface, using a stable dispersion of carbon black, allows to obtain a sensor with improved electrochemical behavior in terms of peak-to-peak separation, current intensity, and the resistance of charge transfer. The results achieved confirm the possibility of printing the electrode on several cost-effective paper-based materials and the improvement of the electrochemical behavior by using carbon black as sustainable nanomaterial.

Tunable Electrical Conductivity of Carbon-Black-Filled Ternary Polymer Blends by Constructing a Hierarchical Structure

A type of hierarchical structured composite composed of a minor thermoplastic polyurethane (TPU) phase spreading at the interface of two major phases polyoxymethylene/polyamide copolymer (POM/COPA) and carbon black (CB) particles selectively localized at the TPU/COPA interface of the tri-continuous blends was fabricated by melt compounding. The hierarchical structure was designed according to predictions and verified by a combination of electron microscopy and solvent extraction technique. The hierarchical structured composites show the dramatically decreased percolation threshold, a reduction of 60% compared to those without TPU where CB is selectively distributed in the COPA phase. The effects of CB contents and TPU on the phase morphology of POM/COPA were investigated, showing the occurrence of the POM/COPA phase inversion from a sea-island to a co-continuous structure beyond the percolation threshold of CB in the presence of TPU. The mechanism for the formation of conductive network is construction of CB network at the TPU/COPA interface of tri-continuous POM/COPA/TPU blends and double percolation effect.

Flexible and Foldable Fully-Printed Carbon Black Conductive Nanostructures on Paper for High-Performance Electronic, Electrochemical, and Wearable Devices

In this work, we demonstrate the first example of fully printed carbon nanomaterials on paper with unique features, aiming the fabrication of functional electronic and electrochemical devices. Bare and modified inks were prepared by combining carbon black and cellulose acetate to achieve high-performance conductive tracks with low sheet resistance. The carbon black tracks withstand extremely high folding cycles (>20 000 cycles), a new record-high with a response loss of less than 10%. The conductive tracks can also be used as 3D paper-based electrochemical cells with high heterogeneous rate constants, a feature that opens a myriad of electrochemical applications. As a relevant demonstrator, the conductive ink modified with Prussian-blue was electrochemically characterized proving to be very promising toward the detection of hydrogen peroxide at very low potentials. Moreover, carbon black circuits can be fully crumpled with negligible change in their electrical response. Fully printed motion and wearable sensors are additional examples where bioinspired microcracks are created on the conductive track. The wearable devices are capable of efficiently monitoring extremely low bending angles including human motions, fingers, and forearm. Here, to the best of our knowledge, the mechanical, electronic, and electrochemical performance of the proposed devices surpasses the most recent advances in paper-based devices.

Array of Chemosensitive Resistors with Composites of Gas Chromatography (GC) Materials and Carbon Black for Detection and Recognition of VOCs: A Basic Study

Mimicking the biological olfaction, large odor-sensor arrays can be used to acquire a broad range of chemical information, with a potentially high degree of redundancy, to allow for enhanced control over the sensitivity and selectivity of artificial olfaction systems. The arrays should consist of the largest possible number of individual sensing elements while being miniaturized. Chemosensitive resistors are one of the sensing platforms that have a potential to satisfy these two conditions. In this work we test viability of fabricating a 16-element chemosensitive resistor array for detection and recognition of volatile organic compounds (VOCs). The sensors were fabricated using blends of carbon black and gas chromatography (GC) stationary-phase materials preselected based on their sorption properties. Blends of the selected GC materials with carbon black particles were subsequently coated over chemosensitive resistor devices and the resulting sensors/arrays evaluated in exposure experiments against vapors of pyrrole, benzenal, nonanal, and 2-phenethylamine at 150, 300, 450, and 900 ppb. Responses of the fabricated 16-element array were stable and differed for each individual odorant sample, proving the blends of GC materials with carbon black particles can be effectively used for fabrication of large odor-sensing arrays based on chemosensitive resistors. The obtained results suggest that the proposed sensing devices could be effective in discriminating odor/vapor samples at the sub-ppm level.

The Toxicological Mechanisms of Environmental Soot (Black Carbon) and Carbon Black: Focus on Oxidative Stress and Inflammatory Pathways

The environmental soot and carbon blacks (CBs) cause many diseases in humans, but their underlying mechanisms of toxicity are still poorly understood. Both are formed after the incomplete combustion of hydrocarbons but differ in their constituents and percent carbon contents. For the first time, “Sir Percival Pott” described soot as a carcinogen, which was subsequently confirmed by many others. The existing data suggest three main types of diseases due to soot and CB exposures: cancer, respiratory diseases, and cardiovascular dysfunctions. Experimental models revealed the involvement of oxidative stress, DNA methylation, formation of DNA adducts, and Aryl hydrocarbon receptor activation as the key mechanisms of soot- and CB-induced cancers. Metals including Si, Fe, Mn, Ti, and Co in soot also contribute in the reactive oxygen species (ROS)-mediated DNA damage. Mechanistically, ROS-induced DNA damage is further enhanced by eosinophils and neutrophils via halide (Cl⁻ and Br⁻) dependent DNA adducts formation. The activation of pulmonary dendritic cells, T helper type 2 cells, and mast cells is crucial mediators in the pathology of soot- or CB-induced respiratory disease. Polyunsaturated fatty acids (PUFAs) were also found to modulate T cells functions in respiratory diseases. Particularly, telomerase reverse transcriptase was found to play the critical role in soot- and CB-induced cardiovascular dysfunctions. In this review, we propose integrated mechanisms of soot- and CB-induced toxicity emphasizing the role of inflammatory mediators and oxidative stress. We also suggest use of antioxidants and PUFAs as protective strategies against soot- and CB-induced disorders.

Nanophotonics-enabled solar membrane distillation for off-grid water purification

With more than a billion people lacking accessible drinking water, there is a critical need to convert nonpotable sources such as seawater to water suitable for human use. However, energy requirements of desalination plants account for half their operating costs, so alternative, lower energy approaches are equally critical. Membrane distillation (MD) has shown potential due to its low operating temperature and pressure requirements, but the requirement of heating the input water makes it energy intensive. Here, we demonstrate nanophotonics-enabled solar membrane distillation (NESMD), where highly localized photothermal heating induced by solar illumination alone drives the distillation process, entirely eliminating the requirement of heating the input water. Unlike MD, NESMD can be scaled to larger systems and shows increased efficiencies with decreased input flow velocities. Along with its increased efficiency at higher ambient temperatures, these properties all point to NESMD as a promising solution for household- or community-scale desalination.

Ozonized carbon black induces mitochondrial dysfunction and DNA damage

Black carbon and tropospheric ozone (O₃ ), which are major air pollutants in China, are hazardous to humans following inhalation. Black carbon can be oxidized by O₃ forming secondary particles of which the health effects are unknown. The present study utilized carbon black as a representative of black carbon to characterize the cytotoxicity induced by secondary particles in bronchial epithelial cells (16HBE) and C57BL/6J mice, and to investigate the implicated molecular pathways. Two types of carbon black including untreated carbon black (UCB) and ozonized carbon black (OCB) were presented. The effects of carbon black on cell viability, intracellular reactive oxygen species (ROS), oxidized/reduced glutathione ratio, mitochondrial membrane potential (MMP), intracellular ATP, and mitochondrial cytochrome c to cytoplasmic cytochrome c ratio were assessed in 16HBE. In addition, an alkaline comet assay and a cytokinesis-block micronucleus (CBMN) test with 16HBE cells in vitro and ELISA method for serum 8-hydroxy-2'-deoxyguanosine (8-OHdG) and a bone marrow micronucleus (BMN) test with C57BL/6J mice in vivo were performed to detect the genotoxicity. When compared with UCB exposed cells, OCB exposed cells had decreased cell viability, increased cell death rate, increased comet length and decreased MMP at 24 h exposure. UCB induced higher level of intracellular ROS than OCB from 4 to 23 h. No changes were observed for both OCB and UCB in serum 8-OHdG, intracellular ATP and mitochondrial cytochrome c to cytoplasmic cytochrome c ratio. The results of CBMN and BMN tests are negative. Intracellular ROS induced by OCB was lower than that of UCB. In summary, ozonization enhances the mitochondrial toxicity and genotoxicity of carbon black. Oxidative stress may not dominate in toxic effects of OCB. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 944-955, 2017.

Linear and Nonlinear Rheology Combined with Dielectric Spectroscopy of Hybrid Polymer Nanocomposites for Semiconductive Applications

The linear and nonlinear oscillatory shear, extensional and combined rheology-dielectric spectroscopy of hybrid polymer nanocomposites for semiconductive applications were investigated in this study. The main focus was the influence of processing conditions on percolated poly(ethylene-butyl acrylate) (EBA) nanocomposite hybrids containing graphite nanoplatelets (GnP) and carbon black (CB). The rheological response of the samples was interpreted in terms of dispersion properties, filler distortion from processing, filler percolation, as well as the filler orientation and distribution dynamics inside the matrix. Evidence of the influence of dispersion properties was found in linear viscoelastic dynamic frequency sweeps, while the percolation of the nanocomposites was detected in nonlinearities developed in dynamic strain sweeps. Using extensional rheology, hybrid samples with better dispersion properties lead to a more pronounced strain hardening behavior, while samples with a higher volume percentage of fillers caused a drastic reduction in strain hardening. The rheo-dielectric time-dependent response showed that in the case of nanocomposites containing only GnP, the orientation dynamics leads to non-conductive samples. However, in the case of hybrids, the orientation of the GnP could be offset by the dispersing of the CB to bridge the nanoplatelets. The results were interpreted in the framework of a dual PE-BA model, where the fillers would be concentrated mainly in the BA regions. Furthermore, better dispersed hybrids obtained using mixing screws at the expense of filler distortion via extrusion processing history were emphasized through the rheo-dielectric tests.

Organophosphorous Pesticide Detection in Olive Oil by Using a Miniaturized, Easy-to-Use, and Cost-Effective Biosensor Combined with QuEChERS for Sample Clean-Up

Herein, we report a portable electrochemical biosensor based on butyrylcholinesterase (BChE) immobilized on carbon black (CB)-modified screen-printed electrodes (SPEs) for the detection of organophosphorous pesticides in olive oil. The BChE/CB-SPE biosensor was developed to detect paraoxon in standard solutions as well as in olive oil samples previously treated with the QuEChERS method to extract pesticides from the whole fatty matrix. The biosensor shows a linear concentration range of between 20 and 100 ppb for paraoxon both in standard solutions (phosphate buffer 0.05 M) and in olive oil extracts, with a detection limit of 6 ppb in olive oil extract, corresponding to 10% of inhibition. The accuracy of this biosensor in olive oil samples was assessed with olive oil spiked with paraoxon, obtaining satisfactory recovery values.

Novel Modifications to Carbon-Based Electrodes to Improve the Electrochemical Detection of Dopamine

In this work, we describe three simple modifications to carbon electrodes that were found to improve the detection of an exemplar neurotransmitter (dopamine) in the presence of physiological interferents (ascorbic acid and/or uric acid). First, the electro-oxidation of ascorbic acid, as a pretreatment, at boron-doped diamond electrode (BDE) interfaces is studied. This treatment did suppress the detection of ascorbic acid oxidation signal, but only in a manner suitable for single-use detection of high concentrations of dopamine (i.e., > 1 μM). Second, the hydrogenation of BDE by electrochemical cathodic treatment and plasma hydrogenation was investigated. Large cathodic, applied potentials (i.e., > - 5 V) and hydrogen plasma pretreatment of BDE lead to the partial and complete oxidization of ascorbic acid before dopamine, respectively. The consequence at hydrogen-plasma treated BDE is the complete electrochemical separation of these two species without any typical catalytic reactions between the analytes. Third, the modification of glassy carbon electrodes with carbon black nanoparticles is explored. This modification enables the simultaneous detection of ascorbic acid, dopamine and uric acid, significantly enhancing the sensitivity of dopamine. Dopamine was best detected using the unconventional route of detecting 5,6-dihydroxyindole, which is made possible by use of carbon-black nanoparticles. The potential of all three studied modifications to be of electroanalytical use is highlighted throughout this work.

Effects of occupational exposure to carbon black on peripheral white blood cell counts and lymphocyte subsets

The International Agency for Research on Cancer has classified carbon black (CB) as a possible (Group 2B) human carcinogen. Given that most CB manufacturing processes result in the emission of various types of chemicals, it is uncertain if the adverse health effects that have been observed in CB-exposed workers are related to CB specifically or are due to other exposures. To address this issue, we conducted a cross-sectional molecular epidemiology study in China of 106 male factory workers who were occupationally exposed to pure CB and 112 unexposed male workers frequency-matched by age and smoking status from the same geographic region. Repeated personal exposure measurements were taken in workers before biological sample collection. Peripheral blood from all workers was used for the complete blood cell count and lymphocyte subsets analysis. Compared to unexposed workers, eosinophil counts in workers exposed to CB were increased by 30.8% (P = 0.07) after adjusting for potential confounders. When stratified by smoking status, statistically significant differences in eosinophils between CB exposed and unexposed workers were only present among never smokers (P = 0.040). Smoking is associated with alterations in various cell counts; however, no significant interaction between CB exposure and smoking status for any cell counts was observed. Given that inflammation, characterized in part by elevated eosinophils in peripheral blood, may be associated with increased cancer risk, our findings provide new biologic insights into the potential relationship between CB exposure and lung carcinogenesis. Environ. Mol. Mutagen. 57:589-604, 2016. © 2016 Wiley Periodicals, Inc.

Static and Dynamic Studies on LiNi1/3 Co1/3 Mn1/3 O2 -Based Suspensions for Semi-Solid Flow Batteries

LiNi1/3 Co1/3 Mn1/3 O2 (LNCM)-based suspensions for semi-solid flow batteries (SSFB) have been investigated by galvanostatic charge/discharge an electrochemical impedance spectroscopy (EIS). The resistance and electrochemical performance of half cells (vs. Li/Li(+) ) as well as the rheological properties are affected by the content of a commercially available electroconductive carbon black [KetjenBlack (KB), AkzoNobel] in the suspensions. In static conditions, a cell with 11.87 and 13.97 % by volume of KB and LNCM delivers high capacity 130 mA h g(-1) at 5 mA cm(-2) , respectively, and a coulombic efficiency of 90 % over 10 injections. The impedance of half cells is dominated by a contact resistance fitted with a resistor and a constant phase element (CPE) in parallel. In flow conditions, cell potential depends on applied current density and measured over potentials are ∼0.3 and 0.7 V for 0.33 and 1 mA cm(-2) , respectively, for a cell containing a suspension with 9.53 % in volume of KB and 13.90 % in volume of LNCM. The effect of the cell contact resistance on the electrochemical performance is discussed.

Improved Durability of Electrocatalyst Based on Coating of Carbon Black with Polybenzimidazole and their Application in Polymer Electrolyte Fuel Cells

Improvement of durability of the electrocatalyst has been the key issue to be solved for the practical application of polymer electrolyte membrane fuel cells. One of the promising strategies to improve the durability is to enhance the oxidation stability of the carbon-supporting materials. In this report, we describe in detail the mechanism of the stability improvement of carbon blacks (CBs; Vulcan and Ketjen) by coating with polybenzimidazole (PBI). Nitrogen adsorption experiments reveal that the PBI coating of CBs results in the capping of the gates of the CB-micropores by the PBI. Since the surface of the micropores inside the CBs are inherently highly oxidized, the capping of such pores effectively prevents the penetration of the electrolyte into the pore and works to avoid the further oxidation of interior of the micropore, which is proved by cyclic voltammogram measurements. Above mechanism agrees very well with the dramatic enhancement of the durability of the membrane electrode assembly fabricated using Pt on the PBI-coated CBs as an electrocatalyst compared to the conventional Pt/CB (PBI-non coated) catalyst.

Relaxation NMR as a tool to study the dispersion and formulation behavior of nanostructured carbon materials

Solvent relaxation NMR has been used to estimate the surface areas and wettability of various types of nanostructured carbon materials in a range of solvents including water, ethanol, and tetrahydrofuran. We illustrate the application of the technique through several short case studies using samples including nanocarbon blacks, graphene oxide, nanographites, and porous graphenes. The technique is shown to give a good measure of surface area, correlating well with conventional surface area estimates obtained by nitrogen adsorption, transmission electron microscopy, or light scattering for the non-porous samples. NMR relaxation has advantages in terms of speed of analysis and being able to use concentrated, wet, and opaque samples. For samples that are porous, two distinct surface areas can be estimated assuming the two environments ('inner' and 'outer') have the same surface chemistry, and that there is a slow exchange of solvent molecules between them. Furthermore, we show that differences in wettability and dispersability between samples dispersed in water, ethanol, and cyclopentanone can be observed, along with changes to the surface chemistry of the interface. Copyright © 2015 John Wiley & Sons, Ltd.

The MTT and Crystal Violet Assays: Potential Confounders in Nanoparticle Toxicity Testing

The toxicological effects of nanoparticles (NPs) on humans, animals, and environment are largely unknown. Assessment of NPs cytotoxicity depends on the choice of the test system. Due to NPs optical activity and absorption values, they can influence the classical cytotoxicity assay. Eight NPs were spiked in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and crystal violet assays and tested with HaCaT human skin cells. The MTT assay standard curve optical density (OD) measurements were altered by the presence of trisilanol phenyl and trisilanol isooctyl polyhedral oligomeric silsesquioxane particles. The crystal violet standard curve OD measurements were significantly shifted by gold NPs, but they did not affect the MTT assay. Carbon black decreased ODs in the MTT and crystal violet assays and was localized in the cell cytoplasm. These findings strongly indicate that a careful choice of in vitro viability systems is required to avoid flawed measurement of NPs toxicity.

Multilayer Graphene/Carbon Black/Chlorine Isobutyl Isoprene Rubber Nanocomposites

High loadings of carbon black (CB) are usually used to achieve the properties demanded of rubber compounds. In recent years, distinct nanoparticles have been investigated to replace CB in whole or in part, in order to reduce the necessary filler content or to improve performance. Multilayer graphene (MLG) is a nanoparticle made of just 10 graphene sheets and has recently become commercially available for mass-product nanocomposites. Three phr (part for hundred rubbers) of MLG are added to chlorine isobutyl isoprene rubber (CIIR)/CB composites in order to replace part of the CB. The incorporation of just 3 phr MLG triples the Young's modulus of CIIR; the same effect is obtained with 20 phr CB. The simultaneous presence of three MLG and CB also delivers remarkable properties, e.g. adding three MLG and 20 phr CB increased the hardness as much as adding 40 phr CB. A comprehensive study is presented, showing the influence on a variety of mechanical properties. The potential of the MLG/CB combination is illustrated to reduce the filler content or to boost performance, respectively. Apart from the remarkable mechanical properties, the CIIR/CB/MLG nanocomposites showed an increase in weathering resistance.

Piezoresistive Soft Condensed Matter Sensor for Body-Mounted Vital Function Applications

A soft condensed matter sensor (SCMS) designed to measure strains on the human body is presented. The hybrid material based on carbon black (CB) and a thermoplastic elastomer (TPE) was bonded to a textile elastic band and used as a sensor on the human wrist to measure hand motion by detecting the movement of tendons in the wrist. Additionally it was able to track the blood pulse wave of a person, allowing for the determination of pulse wave peaks corresponding to the systole and diastole blood pressures in order to calculate the heart rate. Sensor characterization was done using mechanical cycle testing, and the band sensor achieved a gauge factor of 4–6.3 while displaying low signal relaxation when held at a strain levels. Near-linear signal performance was displayed when loading to successively higher strain levels up to 50% strain.

La2O2CO3 Encapsulated La2O3 Nanoparticles Supported on Carbon as Superior Electrocatalysts for Oxygen Reduction Reaction

Constructing nanoscale hybrid materials with unique interfacial structures by using various metal oxides and carbon supports as building blocks are of great importance to develop highly active, economical hybrid catalysts for oxygen reduction reaction (ORR). In this work, La2O2CO3 encapsulated La2O3 nanoparticles on a carbon black (La2O2CO3@La2O3/C) were fabricated via chemical precipitation in an aqueous solution containing different concentrations of cetyltrimethyl ammonium bromide (CTAB), followed by calcination at 750 °C. At a given CTAB concentration 24.8 mmol/L, the obtained lanthanum compound nanoparticles reach the smallest particle size (7.1 nm) and are well-dispersed on the carbon surface. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results demonstrate the formation of La2O2CO3 located on the surface of La2O3 nanoparticles in the hybrid. The synthesized La2O2CO3@La2O3/C hybrid exhibits a significantly enhanced electrocatalytic activity in electrocatalysis experiments relative to pure La2O3, La2O2CO3, and carbon in an alkaline environment, by using the R(R)DE technique. Moreover, its long-term stability also outperforms that obtained by commercial Pt/C catalysts (E-TEK). The exact origin of the fast ORR kinetics is mainly ascribed to the La2O2CO3 layer sandwiched at the interface of carbon and La2O3, which contributes favorable surface-adsorbed hydroxide (-OH(-)(ad)) substitution and promotes active oxygen adsorption at the interfaces. The unique covalent -C-O-C(═O)-O-La-O- bonds, formed at the interfaces between La2O2CO3 and carbon, can act as active sites for the improved ORR kinetics over this hybrid catalyst. Therefore, the fabrication of lanthanum compound-based hybrid material with an unique interfacial structure maybe open a new way to develop carbon-supported metal oxides as next-generation of ORR catalysts.

Solvent Effects on the Photothermal Regeneration of CO2 in Monoethanolamine Nanofluids

A potential approach to reduce energy costs associated with carbon capture is to use external and renewable energy sources. The photothermal release of CO2 from monoethanolamine mediated by nanoparticles is a unique solution to this problem. When combined with light-absorbing nanoparticles, vapor bubbles form inside the capture solution and release the CO2 without heating the bulk solvent. The mechanism by which CO2 is released remained unclear, and understanding this process would improve the efficiency of photothermal CO2 release. Here we report the use of different cosolvents to improve or reduce the photothermal regeneration of CO2 captured by monoethanolamine. We found that properties that reduce the residence time of the gas bubbles (viscosity, boiling point, and convection direction) can enhance the regeneration efficiencies. The reduction of bubble residence times minimizes the reabsorption of CO2 back into the capture solvent where bulk temperatures remain lower than the localized area surrounding the nanoparticle. These properties shed light on the mechanism of release and indicated methods for improving the efficiency of the process. We used this knowledge to develop an improved photothermal CO2 regeneration system in a continuously flowing setup. Using techniques to reduce residence time in the continuously flowing setup, such as alternative cosolvents and smaller fluid volumes, resulted in regeneration efficiency enhancements of over 200%.

[Worker exposure to ultrafine particles during carbon black treatment]

BACKGROUND

The aim of the project was to assess the exposure of workers to ultrafine particles released during handling and packing of carbon black. The assessment included the results of the measurements performed in a carbon black handling plant before, during, and after work shift.

MATERIAL AND METHODS

The number concentration of particles within the dimension range 10-1000 nm and 10-100 nm was assayed by a condensation particle counter (CPC). The mass concentration of particles was determined by a DustTrak II DRX aerosol concentration monitor. The surface area concentration of the particles potentially deposited in the alveolar (A) and tracheo-bronchial (TB) regions was estimated by an AeroTrak 9000 nanoparticle monitor.

RESULTS

An average mass concentration of particles during the process was 6-fold higher than that before its start, while a 3-fold increase in the average number concentration of particles within the dimension range 10-1000 nm and 10-100 nm was observed during the process. At the same time a 4-fold increase was found in the surface area concentration of the particles potentially deposited in the A and TB regions.

CONCLUSIONS

During the process of carbon black handling and packing a significantly higher values of each of the analysed parameters, characterizing the exposure to ultrafine particles, were noted.

Effects of Carbon Black and the Presence of Static Mechanical Strain on the Swelling of Elastomers in Solvent

The effect of carbon black on the mechanical properties of elastomers is of great interest, because the filler is one of principal ingredients for the manufacturing of rubber products. While fillers can be used to enhance the properties of elastomers, including stress-free swelling resistance in solvent, it is widely known that the introduction of fillers yields significant inelastic responses of elastomers under cyclic mechanical loading, such as stress-softening, hysteresis and permanent set. When a filled elastomer is under mechanical deformation, the filler acts as a strain amplifier in the rubber matrix. Since the matrix local strain has a profound effect on the material’s ability to absorb solvent, the study of the effect of carbon black content on the swelling characteristics of elastomeric components exposed to solvent in the presence of mechanical deformation is a prerequisite for durability analysis. The aim of this study is to investigate the effect of carbon black content on the swelling of elastomers in solvent in the presence of static mechanical strains: simple extension and simple torsion. Three different types of elastomers are considered: unfilled, filled with 33 phr (parts per hundred) and 66 phr of carbon black. The peculiar role of carbon black on the swelling characteristics of elastomers in solvent in the presence of mechanical strain is explored.

Reduced pulmonary function and increased pro-inflammatory cytokines in nanoscale carbon black-exposed workers

BACKGROUND

Although major concerns exist regarding the potential consequences of human exposures to nanoscale carbon black (CB) particles, limited human toxicological data is currently available. The purpose of this study was to evaluate if nanoscale CB particles could be responsible, at least partially, for the altered lung function and inflammation observed in CB workers exposed to nanoscale CB particles.

METHODS

Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Brunauer-Emmett-Teller were used to characterize CB. Eighty-one CB-exposed male workers and 104 non-exposed male workers were recruited. The pulmonary function test was performed and pro-inflammatory cytokines were evaluated. To further assess the deposition and pulmonary damage induced by CB nanoparticles, male BALB/c mice were exposed to CB for 6 hours per day for 7 or 14 days. The deposition of CB and the pathological changes of the lung tissue in mice were evaluated by paraffin sections and TEM. The cytokines levels in serum and lung tissue of mice were evaluated by ELISA and immunohistochemical staining (IHC).

RESULTS

SEM and TEM images showed that the CB particles were 30 to 50 nm in size. In the CB workplace, the concentration of CB was 14.90 mg/m³. Among these CB particles, 50.77% were less than 0.523 micrometer, and 99.55% were less than 2.5 micrometer in aerodynamic diameter. The reduction of lung function parameters including FEV1%, FEV/FVC, MMF%, and PEF% in CB workers was observed, and the IL-1β, IL-6, IL-8, MIP-1beta, and TNF- alpha had 2.86-, 6.85-, 1.49-, 3.35-, and 4.87-folds increase in serum of CB workers, respectively. In mice exposed to the aerosol CB, particles were deposited in the lung. The alveolar wall thickened and a large amount of inflammatory cells were observed in lung tissues after CB exposure. IL-6 and IL-8 levels were increased in both serum and lung homogenate.

CONCLUSIONS

The data strongly suggests that nanoscale CB particles could be responsible for the lung function reduction and pro-inflammatory cytokines secretion in CB workers. These results, therefore, provide the first evidence of a link between human exposure to CB and long-term pulmonary effects.

Migration of nanoparticles from plastic packaging materials containing carbon black into foodstuffs

Carbon black was investigated to assess and quantify the possibility that nanoparticles might migrate out of plastic materials used in the food packaging industry. Two types of carbon black were incorporated in low-density polyethylene (LDPE) and polystyrene (PS) at 2.5% and 5.0% loading (w/w), and then subjected to migration studies. The samples were exposed to different food simulants according to European Union Plastics Regulation 10/2011, simulating long-term storage with aqueous and fatty foodstuffs. Asymmetric flow field-flow fractionation (AF4) coupled to a multi-angle laser light-scattering (MALLS) detector was used to separate, characterise and quantify the potential release of nanoparticles. The AF4 method was successful in differentiating carbon black from other matrix components, such as extracted polymer chains, in the migration solution. At a detection limit of 12 µg kg⁻¹, carbon black did not migrate from the packaging material into food simulants. The experimental findings are in agreement with theoretical considerations based on migration modelling. From both the experimental findings and theoretical considerations, it can be concluded that carbon black does not migrate into food once it is incorporated into a plastics food contact material.