Chemie

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Research Data in Chemistry – Results of the first NFDI4Chem Community Survey
(Weinheim : Wiley-VCH, 2020) Herres‐Pawlis, Sonja; Liermann, Johannes C.; Koepler, Oliver
Good research data management (RDM) requires a constant endeavour of the researchers but – first and foremost – user-friendly infrastructure and well accepted standards need to be developed for the researchers. The national research data infrastructure initiative for chemistry in Germany NFDI4Chem sets out to embrace the challenge of creating a general research data management portal and hereby connecting already existing infrastructure as well as to foster the cultural change in chemistry towards digitalization by developing general minimum information standards for all methods used and teaching RDM principles to the community. In order to serve the needs of the chemical community at its best, NFDI4Chem accomplishes regular community surveys. The first survey has been performed in 2019 and the results were condensed into the NFDI4Chem proposal. This article summarizes the design of the study and its results. With regard to the project development, this first national survey serves as zero-point of all upcoming efforts in research data management.
Toward Continuous Electrochemical Synthesis of Ferrate
(Weinheim : Wiley-VCH, 2024) Kupec, Robin; Plischka, Wenzel; Duman, Ediz; Schneider, Selina; Weidlich, Claudia; Wessling, Matthias; Keller, Robert; Stöckl, Markus
Ferrate (Fe(VI)) is of great interest in energy storage solutions, organic synthesis, and wastewater treatment due to its decent oxidation potential and non-toxic end-product formation, making it a green oxidizer. The electrochemical generation of ferrate in NaOH at current densities of j ≥ 100 mA cm−2 is presented using low-cost sacrificial iron anodes, mild steel, and spheroidal graphite cast iron (ductile iron). Under optimized reaction parameters with 40 wt.% (14 m) NaOH and a ZrO2-based diaphragm, spheroidal graphite cast iron shows no signs of passivation in 5 h experiments even at j = 150 mA cm−2. The results are used in a novel electrolysis cell with a combined geometric anode surface area of 230 cm2, incorporated in a mini-plant suitable for continuous synthesis. This setup produces a peak ferrate concentration of 10.1 g L−1 (84 mm) after 5 h in 1.6 L anolyte volume, resulting in a total ferrate mass of 16.2 g. Optimal electrolysis temperatures are between 35 and 50 °C. The highest current efficiency is 63.0%, and the lowest specific energy consumption is 9.2 kWh kg−1 ferrate. The presented work is an essential step toward the continuous electrochemical synthesis of ferrate using sacrificial anodes under basic conditions.
All Electrochemical Synthesis of Performic Acid Starting from CO2, O2, and H2O
(Weinheim : Wiley-VCH, 2025) Dinges, Ida; Pyschik, Markus; Schütz, Julian; Schneider, Selina; Klemm, Elias; Waldvogel, Siegfried R.; Stöckl, Markus
Driven by anthropogenic climate change, innovative approaches to defossilize the chemical industry are required. Herein, the first all-electrochemical feasibility study for the complete electrosynthesis of the strong oxidizer and effective disinfectant performic acid is presented. Its synthesis is achieved solely from CO2, O2, and H2O in a two-step process. Initially, CO2 is electrochemically reduced to formate employing Bi2O3-based gas diffusion electrodes in a phosphate-buffered electrolyte. Thereby, high formate concentration (500.7 ± 0.6 mmol L−1) and high Faradaic efficiency (86.3 ± 0.3%) are achieved at technically relevant current density (150 mA cm−2). Subsequently, the formate acts as (storable) feed electrolyte for the second electrolysis step. Employing carbon-based gas diffusion electrodes, O2 is reduced to H2O2 and performic acid is directly formed in situ. As before, high H2O2 concentration (1.27 ± 0.06 mol L−1) and high Faradaic efficiency (85.3 ± 5.4%) are achieved. Furthermore, performic acid concentration suitable for disinfection is obtained (82 ± 11 mmol L−1). In summary, this innovative feasibility study highlights the potential of combining electrochemical CO2 reduction with H2O2 electrosynthesis, which could provide sustainable access to performic acid in the future.
Coupling of CO2 Electrolysis with Parallel and Semi- Automated Biopolymer Synthesis – Ex-Cell and without Downstream Processing
(Weinheim : Wiley-VCH, 2024) Dinges, Ida; Depentori, Ina; Gans, Lisa; Holtmann, Dirk; Waldvogel, Siegfried R.; Stöckl, Markus
Important improvements have been achieved in developing the coupling of electrochemical CO2 reduction to formate with its subsequent microbial conversion to polyhydroxybutyrate (PHB) by Cupriavidus necator. The CO2 based formate electrosynthesis was optimised by electrolysis parameter adjustment and application of Sn based gas diffusion electrodes reaching almost 80 % Faradaic efficiency at 150 mA cm−2. Thereby, catholyte with the high formate concentration of 441±9 mmol L−1 was generated as feedstock without intermediate downstream processing for semi-automated formate feeding into a fed-batch reactor system. Moreover, microbial formate conversion to PHB was studied further, optimised, and successfully scaled from shake flasks to semi-automated bioreactors. Therein, a PHB per formate ratio of 16.5±4.0 mg g−1 and a PHB synthesis rate of 8.4±2.1 mg L−1 OD−1 h−1 were achieved. By this process combination, an almost doubled overall process yield of 22.3±5.5 % was achieved compared to previous reports. The findings allow a detailed evaluation of the overall CO2 to PHB conversion, providing the basis for potential technical exploitation.
Geopolymer Based Electrodes as New Class of Material for Electrochemical CO2 Reduction
(Weinheim : Wiley-VCH, 2023) Schuster, Jürgen; Ukrainczyk, Neven; Koenders, Eddie; Stöckl, Markus
To achieve a successful transition to a sustainable carbon and energy management, it is essential to both reduce CO2 emissions and develop new technologies that utilize CO2 as a starting substrate. In this study, we demonstrate for the first-time the functionalization of geopolymer binder (GP) with Sn for electrochemical CO2 reduction (eCO2RR) to formate. By substituting cement with Sn-GP, we have merged CO2 utilisation and emission reduction. Using a simple mixing procedure, we were able to obtain a pourable mortar containing 5 vol. % Sn-powder. After hardening, the Sn-GP electrodes were characterized for their mechanical and CO2 electrolysis performance. In 10 h electrolyses, formate concentrations were as high as 22.7±0.9 mmol L−1 with a corresponding current efficiency of 14.0±0.5 % at a current density of 20 mA cm−2. Our study demonstrates the successful design of GP-electrodes as a new class of hybrid materials that connect eCO2RR and construction materials.
Parallel paired electrolysis of green oxidizing agents by the combination of a gas diffusion cathode and boron-doped diamond anode
(Lausanne : Frontiers Media, 2024) Hamm, Christin M.; Schneider, Selina; Hild, Stefanie; Neuber, Rieke; Matthée, Thorsten; Krümberg, Jens; Stöckl, Markus; Mangold, Klaus-Michael; Kintrup, Jürgen
The generation of “green” oxidizing agents by electrochemical synthesis opens the field for sustainable, on-demand, and on-site production, which is often based on non-critical starting materials. In this study, electrosyntheses were carried out on different cathode and anode materials. In half-cell experiments, the cathodic synthesis of peracetic acid (PAA) was investigated on gas diffusion electrodes (GDEs), reaching 22.6 mmol L−1 of PAA with a current efficiency (CE) of 7.4%. Moreover, peroxodicarbonate (PODIC®) was produced anodically on boron-doped diamond (BDD) electrodes with concentrations as high as 42.7 mmol L−1 PODIC® and a CE of 30.3%. Both cathodic and anodic processes were individually examined and improved. Finally, the half-cell reactions were combined as a proof of concept in a parallel paired electrolysis cell for the first time to achieve an increased overall CE.
Multifilament fibres of poly(ε-caprolactone)/poly(lactic acid) blends with multiwalled carbon nanotubes as sensor materials for ethyl acetate and acetone
(Amsterdam [u.a.] : Elsevier, 2011) Rentenberger, Rosina; Cayla, Aurélie; Villmow, Tobias; Jehnichen, Dieter; Campagne, Christine; Rochery, Maryline; Devaux, Eric; Pötschke, Petra
Conductive poly(ε-caprolactone) (PCL) + 4% multiwalled carbon nanotubes (MWCNTs)/poly(lactic acid) (PLA) = 50/50 wt% blend multifilament fibres were melt-spun and a woven textile was made by a handloom with the conductive fibres in weft direction. The fibres were tested for cyclic liquid sensing in ethyl acetate and acetone as two moderate solvents and in ethanol as a poor solvent. The liquid sensing responses, namely the relative resistance changes Rrel relating the resistance change to the initial resistance of the samples on contact with ethyl acetate and acetone, were fast (R rel higher than 16 after 100 s), with high amplitudes (R rel higher than 23 after 500 s), and well reproducible. At the same time, the fibres were resistant against these solvents. The response to ethanol was also reproducible, however, very slow and with low amplitude. PLA was found to crystallize during the immersion process, whereas in PCL the crystalline domains transformed into amorphous ones as studied by Wide Angle X-ray Diffraction. The crystallization of PLA does not influence negatively the liquid sensing properties which can be assigned to the finding that the MWCNT are predominantly localized in the PCL phase as confirmed by Scanning Electron Microscopy. In the final step, a textile based on those fibres was prepared and its sensing behaviour was investigated on ethyl acetate and acetone clearly showing that such textiles are suitable to detect these solvents.
Attenuation of electromagnetic waves by carbon nanotube composites
(Amsterdam [u.a.] : Elsevier, 2008) Hornbostel, Björn; Leute, Ulrich; Pötschke, Petra; Kotz, Jochen; Kornfeld, Daniela; Chiu, Po-Wen; Roth, Siegmar
Experiments on polycarbonate/single-walled carbon nanotube composites were performed to explore the potential of carbon nanotubes in attenuating electromagnetic waves. According to the results of these experiments a distinct effect is present. The effect is dependent on the tubular filler properties and on the morphology of the composite. At a loading of 5.4 wt% single-walled carbon nanotubes in polycarbonate an attenuation of the field of 47 dB could be detected, which corresponds an attenuation of the power of 99.998%.
Ductile-to-semiductile transition in PP-MWNT nanocomposites
(Weinheim : Wiley-VCH, 2007) Satapathy, Bhabani K.; Ganß, Martin; Weidisch, Roland; Pötschke, Petra; Jehnichen, Dieter; Keller, Thomas; Jandt, Klaus D.
A ductile-to-semiductile transition in the crack resistance behaviour of PP/MWNT composites is discussed, using an essential work of fracture approach based on a post yield fracture mechanics concept and its possible interrelation to the structural attributes studied by TEM, SEM, and WAXD. A maximum in the non-essential work of fracture is observed at 0.5 wt-% MWNT content, which demonstrates the enhanced resistance to crack propagation compared to pure PP, followed by a sharp decline with the increase in MWNT content to 1.5 wt.-%, which reveals a ductile-to-semiductile transition. Fracture kinetic studies present a qualitative picture of the nature of such a transition in terms of a) switch over from non-steady (in pure PP) to steady-state crack tip opening displacement rate (in nanocomposites), and b) a ductile-to-semiductile transition largely as a result of delayed- yielding of the nanocomposites.
Vapor sensing properties of thermoplastic polyurethane multifilament covered with carbon nanotube networks
(Amsterdam [u.a.] : Elsevier, 2011) Fan, Qingqing; Qin, Zongyi; Villmow, Tobias; Pionteck, Jürgen; Pötschke, Petra; Wu, Yongtao; Voit, Brigitte; Zhu, Meifang
The volatile organic compound (VOC) vapor sensing properties of a novel kind of thermoplastic polyurethane multifilament - carbon nanotubes (TPU-CNTs) composites is studied. And the sensing is based on changes in the electrical resistance of the composites due to vapor contact. The composites were readily obtained by adhering CNTs on the surface layer of TPU by means of simply immersing pure TPU multifilament into CNT dispersion. The uniformly formed nanotube networks on the outer layer of composite multifilament are favorable for providing efficient conductive pathways. The resulting TPU-CNTs composites show good reproducibility and fast response (within seconds) of electrical resistance change in cyclic exposure to diluted VOC and pure dry air. The vapor sensing behaviors of the composites are related to CNT content, vapor concentration, and polar solubility parameters of the target vapors. A relatively low vapor concentration of 0.5% is detectable, and a maximum relative resistance change of 900% is obtained for the composite with 0.8 wt.% CNT loading when sensing 7.0% chloroform. It is proposed that both the disconnection of CNT networks caused by swelling effects of the TPU matrix and the adsorption of VOC molecules on the CNTs are responsible for the vapor sensing behavior of TPU-CNTs composite, while the former effect plays the major role.
Liquid sensing of melt-processed poly(lactic acid)/multi-walled carbon nanotube composite films
(Amsterdam [u.a.] : Elsevier, 2008) Kobashi, Kazufumi; Villmow, Tobias; Andres, Timo; Pötschke, Petra
Liquid sensing properties of poly(lactic acid) (PLA)/multi-walled carbon nanotube (MWNT) composites were studied on the basis of the change of electrical properties on solvent contact. The composites were prepared by melt processing using a twin screw extruder. The MWNT loading differed between 0.5 and 2.0 wt%, and an electrical percolation threshold below 0.5 wt% MWNT content was obtained. TEM observations revealed that the nanotubes form a conductive network structure in the PLA matrix, which is the key for liquid sensing. Electrical resistance of the composites was monitored in solvent immersion/drying cycles on samples prepared from thin pressed composite sheets. The resistance reversibly changed upon the cycles with good reproducibility. Lower MWNT loadings resulted in larger resistance changes, indicating that the conductive MWNT network tends to readily disconnect due to the less dense structures as compared to higher loadings. Various solvents (n-hexane, toluene, chloroform, tetrahydrofuran, dichloromethane, ethanol, and water) were successfully detected, showing different degrees of the resistance changes (ca. 4-1.0 × 103 Ω) and the relative resistance changes (ca. 0.003-3.0 × 103). The solubility parameters of the solvents were found to be good indicators to estimate liquid sensing properties of these PLA/MWNT composites for the poor and good solvents.
Rheological characterization of melt processed polycarbonate-multiwalled carbon nanotube composites
(Amsterdam : Elsevier, 2005) Abdel-Goad, Mahmoud; Pötschke, Petra
In this study polycarbonate/multiwalled carbon nanotube composites were produced with different compositions by diluting a masterbatch using melt mixing in a DACA-Micro-Compounder. The composites were rheologically characterized using an ARES-rheometer in the dynamic mode under nitrogen atmosphere at 280 °C and frequency varying from 100 to 0.056 rad/s. The results showed that the dynamic moduli and the viscosity increased with increasing MWNT content. At a concentration of 0.5 wt.% MWNT, a significant change in the frequency dependence of the moduli was observed which indicates a transition from a liquid like to a solid like behavior of the nanocomposites. This transition can be related to the formation of a combined network between the nanotubes and the polymer chains.
Melt mixing of polycarbonate with multiwalled carbon nanotubes: Microscopic studies on the state of dispersion
(New York, NY [u.a.] : Elsevier, 2004) Pötschke, Petra; Bhattacharyya, Arup R.; Janke, Andreas
The focus of the paper is to investigate several issues related to the state of dispersion of multiwalled carbon nanotubes (MWNTs) in a polycarbonate (PC) matrix. A masterbatch of PC-MWNT (15 wt.%) was diluted with different amounts of PC in a small scale conical twin screw extruder (DACA Micro Compounder) to obtain different compositions of MWNT. In this system, electrical measurements indicated percolation of MWNT between 1.0 and 1.5 wt.%. We report TEM and AFM investigations of the state of dispersion of MWNT, in the entire volume of the matrix, in selected composites with compositions below (1 wt.% MWNT) and above the percolation threshold (2 and 5 wt.% MWNT). In addition, it was investigated if surface segregation of MWNT and flow induced orientation of nanotubes within the extruded strands had been occurred. It is found that the nanotubes dispersed uniformly through the matrix showing no significant agglomeration in the compositions studied. TEM micrographs seem to be able to detect the percolated structure of the carbon nanotubes. Furthermore, by comparing AFM micrographs from the core region and near to surface region no evidence of segregation or depletion of MWNT at the surface of the extruded strand was found. Comparison of TEM and AFM micrographs on surfaces cut along and perpendicular to the strand direction led to the conclusion that no preferred alignment had occurred as a result of extrusion. Aside from TEM technique, AFM is shown to be suitable to characterize the state of nanotube dispersion along with the issue of surface segregation and orientation of the nanotubes.
Fire behaviour of polyamide 6/multiwall carbon nanotube nanocomposites
(New York, NY [u.a.] : Elsevier, 2005) Schartel, B.; Pötschke, Petra; Knoll, U.; Abdel-Goad, M.
Nanocomposites of polyamide 6 with 5 wt.% multiwall carbon nanotubes are investigated to clarify their potential as regards the fire retardancy of polymers. The nanocomposites are investigated using SEM, electrical resistivity, and oscillatory shear rheology. The pyrolysis is characterized using thermal analysis. The fire behaviour is investigated with a cone calorimeter using different external heat fluxes, by means of the limiting oxygen index and the UL 94 classification. The fire residue is characterized using SEM. The comprehensive fire behaviour characterization not only allows the materials' potential for implementation in different fire scenarios and fire tests to be assessed, but also provides detailed insight into the active mechanisms. The increased melt viscosity of the nanocomposites and the fibre-network character of the nanofiller are the dominant mechanisms influencing fire performance. The changes are found to be adjuvant with respect to forced flaming conditions in the cone calorimeter, but also deleterious in terms of flammability.
Electrical, rheological and morphological studies in co-continuous blends of polyamide 6 and acrylonitrile-butadiene-styrene with multiwall carbon nanotubes prepared by melt blending
(Amsterdam [u.a.] : Elsevier, 2009) Bose, Suryasarathi; Bhattacharyya, Arup R.; Kulkarni, Ajit R.; Pötschke, Petra
Multiwall carbon nanotubes (MWNT) were incorporated in melt-mixed co-continuous blends of polyamide 6 (PA6) and acrylonitrile-butadiene-styrene (ABS) using a conical twin-screw microcompounder. The state of dispersion of MWNT in the blends was assessed through AC electrical conductivity measurements and melt-rheological investigations. The electrical and rheological percolation threshold in PA6/ABS blends was ∼3-4 and ∼1-2 wt% MWNT, respectively. A unique reactive modifier (sodium salt of 6-amino hexanoic acid, Na-AHA) was employed to facilitate 'network-like' structure of MWNT and to confine them in a specific phase. This was achieved by establishing specific interactions with the delocalized 'π-electron' clouds of MWNT and melt-interfacial reaction during melt-mixing. The electrical percolation threshold was significantly reduced in the blends (∼0.25 wt%) in the presence of Na-AHA modified MWNT and even coincided with the rheological percolation threshold. Significant refinement in the co-continuous structure was also observed in the presence of Na-AHA modified MWNT.
Use of carbon nanotube filled polycarbonate in blends with montmorillonite filled polypropylene
(Amsterdam [u.a.] : Elsevier, 2007) Pötschke, Petra; Kretzschmar, Bernd; Janke, Andreas
Blends were prepared by melt mixing from a conductive polycarbonate composite filled with multiwalled carbon nanotubes (MWNT) and polypropylene containing clay (montmorillonite, MMT). The PC composite, containing 2 wt% MWNT (PC-2NT), was prepared by diluting a PC masterbatch by melt extrusion. The PP nanoclay composite with 3 wt% MMT (PP-3MMT) was produced by melt compounding. Blends were prepared in a small scale Daca Microcompounder over the whole composition range. The aim of the study was to produce conductive blends containing less MWNT than required for the pure PC by using the concept of double percolation through the formation of a co-continuous morphology. The fully co-continuous morphology range was found between 40 and 80 wt% of the filled PC phase. A significant increase in electrical conductivity could be obtained in the composition range starting at 50 wt% (MWNT content about 0.6 vol%). In this range the filled PC forms a continuous phase. Whereas in the blends the MWNT were still dispersed homogeneously within the PC phase, the MMT segregated from the PP towards the blend interface.
Liquid sensing properties of melt processed polypropylene/poly(ε-caprolactone) blends containing multiwalled carbon nanotubes
(Amsterdam [u.a.] : Elsevier, 2011) Pötschke, Petra; Kobashi, Kazufumi; Villmow, Tobias; Andres, Timo; Paiva, Maria Conceição; Covas, José António
The sensing properties of polypropylene (PP)/poly(ε-caprolactone) (PCL) blends containing multiwalled carbon nanotubes (MWNT) were studied in terms of their electrical resistance change in presence of liquids (solvents). The preparation of co-continuous blends based on the double percolation concept was done by melt mixing of electrically conductive PCL composites containing 3. wt.% MWNT and neat PP in ratios of 30:70, 40:60, and 50:50. The electrical resistance change of the PCL-MWNT composites and blends was monitored in a solvent immersion/drying cycle. Various solvents, such as n-hexane, ethanol, methanol, water, toluene, chloroform, and tetrahydrofuran were successfully detected, yielding different responses and reversibility of the resistance changes.PP and PCL were tested separately for solvent sorption using ethanol and n-hexane, both showing a low sorption of n-hexane. Ethanol sorption was large for PCL and almost absent for PP. The 50/50 blend composites with 3. wt.% MWNT in the PCL phase presented larger resistance changes for n-hexane, showing larger sensing ability for this solvent compared to PCL composites with 1 and 3. wt.% loadings. The opposite response was observed for immersion in ethanol where the PCL-MWNT composites showed larger changes than the blends. As the ratio of the conductive PCL phase over PP in the blend composition (i.e. the overall MWNT content) decreased, larger resistance changes were observed. The liquid sensing properties of compression-moulded discs and melt-drawn filaments were compared indicating higher responses for the discs.
Highly conducting poly(methyl methacrylate)/carbon nanotubes composites: Investigation on their thermal, dynamic-mechanical, electrical and dielectric properties
(Amsterdam [u.a.] : Elsevier, 2011) Logakis, E.; Pandis, C.; Pissis, P.; Pionteck, J.; Pötschke, Petra
Nanocomposites of poly(methyl methacrylate) (PMMA) containing various multi-walled carbon nanotubes (MWCNT) contents were prepared using melt mixing. Several techniques were employed to study the influence of the MWCNT addition on the thermal, mechanical, electrical and dielectric properties of the PMMA matrix. The electrical percolation threshold (pc) was found to be 0.5vol.% by performing AC and DC conductivity measurements. Significantly high conductivity levels (σdc) were achieved: σdc exceeds 10-2S/cm already at 1.1vol.%, the criterion for EMI shielding (σdc>10-1S/cm) is fulfilled at 2.9vol.%, and the highest loaded sample (5.2vol.%) gave a maximum value of 0.5S/cm. Dielectric relaxation spectroscopy measurements in broad frequency (10-1-106Hz) and temperature ranges (-150 to 170°C) indicated weak polymer-filler interactions, in consistency with differential scanning calorimetry and dynamic-mechanical analysis findings. Weak polymer-filler interactions and absence of crystallinity facilitate the achievement of high conductivity levels in the nanocomposites.
Influence of injection molding parameters on the electrical resistivity of polycarbonate filled with multi-walled carbon nanotubes
(Amsterdam [u.a.] : Elsevier, 2008) Villmow, Tobias; Pegel, Sven; Pötschke, Petra; Wagenknecht, Udo
Two polycarbonate (PC) composites with 2 and 5 wt% multi-walled carbon nanotube (MWNT) content were injection molded using a two-level, four-factor factorial design to evaluate the influences of holding pressure, injection velocity, mold temperature, and melt temperature on the electrical surface and volume resistivities. For both composites variations in resistivity of the injection-molded plates up to six orders of magnitude were found. The highest impact was determined for the injection velocity followed by the melt temperature and the interaction of both. The resistivity varied also locally within the plates showing differences up to five orders of magnitude for 2 wt% and up to two orders for 5 wt% MWNT. Thereby, areas of equal resistivity are formed in a semicircular shape with values increasing with the flow path. Transmission electron microscopy (TEM) investigations indicated a skin layer with highly oriented nanotubes in case of high injection velocity and low melt temperature, but a network-like structure even in the skin area at low injection velocity and high melt temperature.
Influence of screw configuration, residence time, and specific mechanical energy in twin-screw extrusion of polycaprolactone/multi-walled carbon nanotube composites
(Amsterdam [u.a.] : Elsevier, 2010) Villmow, Tobias; Kretzschmar, Bernd; Pötschke, Petra
Melt processing of thermoplastic-based nanocomposites is the favoured route to produce electrically conductive or electrostatic dissipative polymer composites containing carbon nanotubes (CNT). As these properties are desired at low filler fractions, a high degree of dispersion is required in order to benefit from the intrinsic CNT properties. This study discusses the influence of screw configuration, rotation speed, and throughput on the residence time and specific mechanical energy (SME) and the resulting macroscopic CNT dispersion in polycaprolactone (PCL) based masterbatches containing 7.5 wt.% multi-walled carbon nanotubes (MWNT) using an intermeshing co-rotating twin-screw extruder Berstorff ZE25. The processing conditions were found to have a strong influence on the residence time (tR) of the extrudates and on the CNT dispersion within the masterbatches as assessed using light microscopy. Both, an increase of rotation speed and throughput resulted in a decrease of tR whereas the use of back-conveying elements and the extension of the processing length showed the opposite effect. As the increase of rotation speed results in higher SME inputs a significant increase of CNT dispersion was found, whereas an increase of throughput resulted in worse dispersion. Beside these machine parameters, the design of the screw can further promote the CNT dispersion especially when using distributive screw configurations containing mixing elements. The lowest area fraction of undispersed primary MWNT agglomerates within PCL masterbatches was found when using an extended distributive screw having a length to diameter ratio L/. D of 48 instead of 36. The few remaining macroscopic agglomerates could be entirely dispersed in a subsequent masterbatch dilution process resulting in a very low electrical percolation threshold of 0.24 vol.% MWNT.

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