59 results on '"Regine Boldt"'
Search Results
2. Dopamine as a bioinspired adhesion promoter for the metallization of multi-responsive phase change microcapsules
- Author
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Cordelia Zimmerer, Giulia Fredi, Sascha Putzke, Regine Boldt, Andreas Janke, Beate Krause, Astrid Drechsler, and Frank Simon
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science - Abstract
This work reports on an environmentally friendly method to produce encapsulated phase change material with a thin nickel coating, applicable for heat conversion, storage and thermal management of heat-sensitive components and suitable for active heating by electromagnetic radiation. A critical issue for the metallization is the adhesion between the polymer capsule shell and the metal layer. Based on previous studies using the bio-molecule dopamine as adhesion promoter in composites and for plastics metallization, commercial paraffin microcapsules were coated with an ultrathin polydopamine film via a simple wet chemical process. Subsequently, a thin, uniform and compact nickel layer was produced by electroless metallization. The successful deposition of both layers was verified with a broad range of imaging and spectroscopic techniques. For the first time, surface-enhanced IR spectroscopy was used to study the deposition of ultrathin PDA films. The combination of SEM and energy-dispersive X-ray spectroscopy allowed resolving the spatial distribution of the elements Ni, N, and O in the MC shell. Electrically conducting paths in the Ni shell were verified by conductive AFM. Thermal analysis revealed that the coated microcapsules show a phase change enthalpy of approx. 170 J/g, suitable for thermal storage and management. Additionally, the nickel layer enhanced the thermal diffusivity of the microcapsule powders and enables a fast heating of the PCM microcapsules by microwave radiation, demonstrating the applicability of the metallized MCs for controlled heating applications. Graphical abstract
- Published
- 2022
3. Ecofriendly Removal of Aluminum and Cadmium Sulfate Pollution by Adsorption on Hexanoyl-Modified Chitosan
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Berthold Reis, Konstantin B. L. Borchert, Martha Kafetzi, Martin Müller, Karina Haro Carrasco, Niklas Gerlach, Christine Steinbach, Simona Schwarz, Regine Boldt, Stergios Pispas, and Dana Schwarz
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modified chitosan ,heavy metal ion adsorption ,cadmium and aluminum removal ,pH stable chitosan ,wastewater treatment ,General Medicine - Abstract
The purity and safety of water as a finite resource is highly important in order to meet current and future human needs. To address this issue, the usage of environmentally friendly and biodegradable adsorbers and flocculants is essential. Chitosan, as a biopolymer, features tremendous properties as an adsorber and flocculant for water treatment. For the application of chitosan as an adsorber under acidic aqueous conditions, such as acid mine drainage, chitosan has been modified with hydrophobic hexanoyl chloride (H-chitosan) to reduce the solubility at a lower pH. In order to investigate the influence of the substitution of the hexanoyl chloride on the adsorption properties of chitosan, two chitosans of different molecular weights and of three different functionalization degrees were analyzed for the adsorption of CdSO4(aq) and Al2(SO4)3(aq). Among biobased adsorbents, H-chitosan derived from the shorter Chitosan exhibited extraordinarily high maximum adsorption capacities of 1.74 mmol/g and 2.06 mmol/g for Cd2+ and sulfate, and 1.76 mmol/g and 2.60 mmol/g for Al3+ and sulfate, respectively.
- Published
- 2022
4. Multiple-Ring Aromatic Cation Engineering in Low-Dimensional Perovskites
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Andrei Mitrofanov, Yonder Berencén, Elaheh Sadrollahi, Regine Boldt, David Bodesheim, Hendrik Weiske, Fabian Paulus, Agnieszka Kuc, and Brigitte Voit
- Published
- 2022
5. Blooming of insecticides from polyethylene mesh and film
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Dennis Moyo, António Benjamim Mapossa, Walter Wilhelm Focke, Regine Boldt, Mthoko Mayibongwe Sibanda, Taneshka Kruger, James Wesley-Smith, and René Androsch
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medicine.medical_specialty ,Vector control ,business.industry ,Public health ,General Medicine ,medicine.disease ,Environmental health ,Component (UML) ,medicine ,General Earth and Planetary Sciences ,Disease prevention ,General Agricultural and Biological Sciences ,business ,Malaria ,General Environmental Science - Abstract
Malaria remains a public health concern with vector control still the vital component of disease prevention, control, and elimination strategies. Recent years has seen a “stalling” in the progress ...
- Published
- 2021
6. Shear-induced crystallization of polyamide 11
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Regine Boldt, Maria Laura Di Lorenzo, Katalee Jariyavidyanont, Salvatore Mallardo, René Androsch, Pierfrancesco Cerruti, and Alicyn M. Rhoades
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Shearing (physics) ,Superstructure ,Materials science ,Rheometer ,Semicrystalline morphology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Specific work of flow ,0104 chemical sciences ,law.invention ,Shear rate ,Crystal ,Shear (sheet metal) ,law ,Polyamide ,General Materials Science ,Composite material ,Crystallization ,0210 nano-technology ,Polyamide 11 ,Shear-induced nucleation/crystallization - Abstract
Shear-induced formation of crystal nuclei in polyamide 11 (PA 11) was studied using a conventional parallel-plate rheometer. Crystallization of PA 11 after shearing the melt at different rates for 60 s was followed by the evolution of the complex viscosity. The sheared samples showed in an optical microscope a gradient structure along the radius, due to the increasing shear rate from the center to the edge. The critical shear rate for shear-induced formation of nuclei was identified at the position where a distinct change of the semicrystalline superstructure is observed, being at around 1 to 2 s−1. Below this threshold, a space-filled spherulitic superstructure developed as in quiescent-melt crystallization. Above this value, after shearing at rates between 1 and 5 s−1, an increased number of point-like nuclei was detected, connected with formation of randomly oriented crystals. Shearing the melt at even higher rates led to a further increase of the nuclei number and growth of crystals oriented such that the chain axis is in parallel to the direction of flow. In addition, optical microscopy confirmed formation of long fibrillar structures after shearing at such condition. The critical specific work of flow of PA 11 was calculated to allow a comparison with that of polyamide 66 (PA 66). This comparison showed that in the case of PA 11 more work for shear-induced formation of nuclei is needed than in the case of PA 66, discussed in terms of the chemical structure of the repeat unit in the chains. Graphical abstract
- Published
- 2021
7. Improved Rheology, Crystallization, and Mechanical Performance of PLA/mPCL Blends Prepared by Electron-Induced Reactive Processing
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Regine Boldt, Sven Wießner, Michael Thomas Müller, Ying Huang, Carsten Zschech, and Uwe Gohs
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Materials science ,Renewable Energy, Sustainability and the Environment ,General Chemical Engineering ,technology, industry, and agriculture ,Bio based ,Chemical free ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Toughening ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,Chemical engineering ,Rheology ,chemistry ,law ,Polycaprolactone ,Environmental Chemistry ,Crystallization ,0210 nano-technology - Abstract
Biodegradable polylactide/modified polycaprolactone (PLA/mPCL) blends were successfully prepared by sustainable electron-induced reactive processing (EIReP) without introducing any chemical compati...
- Published
- 2021
8. Crystallinity effect on electron-induced molecular structure transformations in additive-free PLA
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Yinglan Zhang, Michael Thomas Müller, Regine Boldt, and Markus Stommel
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Polymers and Plastics ,Organic Chemistry ,Materials Chemistry - Published
- 2023
9. Crystallization-Induced Polymer Scaffold Formation in the Polymer/Drug Delivery System Poly(l-lactic acid)/Ethyl Butylacetylaminopropionate (PLLA/IR3535)
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Georg Hillrichs, Hande Ece Yener, René Androsch, Fanfan Du, and Regine Boldt
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Materials science ,Polymers and Plastics ,Polymers ,Polyesters ,Bioengineering ,law.invention ,Biomaterials ,Drug Delivery Systems ,law ,Materials Chemistry ,Animals ,Humans ,Polymer scaffold ,Crystallization ,chemistry.chemical_classification ,fungi ,Microporous material ,Polymer ,Controlled release ,Evaporation (deposition) ,Solvent ,Chemical engineering ,chemistry ,Drug delivery ,Propionates - Abstract
Polymer/mosquito-repellent scaffolds exhibit increasing importance in long-lasting human skin protection to be used as wearable devices and allowing for controlled release of repellents. In this study, ethyl butylacetylaminopropionate (IR3535) was used as a human and environmental friendly active mosquito-repellent serving as a solvent to form functional poly(l-lactic acid) (PLLA) scaffolds by crystallization-based solid-liquid thermally induced phase separation. Crystallization of PLLA in the presence of IR3535 is faster than melt-crystallization of neat PLLA, and in the investigated concentration range from 5 to 50 mass % PLLA, its maximum crystallization rate increases with the PLLA content, by both, increases of the maximum crystal growth rate and of the nuclei density. By adjusting the polymer concentration and the crystallization temperature, microporous scaffolds of different fine structures are obtained, hosting the mosquito-repellent in intra- and interspherulitic pores for its intended later evaporation.
- Published
- 2021
10. Meso- and macroporous silica-based arsenic adsorbents: effect of pore size, nature of the active phase, and silicon release
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Konstantin B. L. Borchert, Dana Schwarz, Valentina Mameli, Claudio Cara, Regine Boldt, Marco Sanna Angotzi, Christine Steinbach, and Carla Cannas
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Silicon ,General Engineering ,chemistry.chemical_element ,Bioengineering ,Sorption ,General Chemistry ,Atomic and Molecular Physics, and Optics ,Adsorption ,chemistry ,Chemical engineering ,Surface modification ,General Materials Science ,Water treatment ,Porosity ,Dissolution ,Arsenic - Abstract
Arsenic pollution in ground and drinking water is a major problem worldwide due to the natural abundance of arsenic by dissolution from ground sediment or mining activities from anthropogenic activities. To overcome this issue, iron oxides as low-cost and non-toxic materials, have been widely studied as efficient adsorbents for arsenic removal, including when dispersed within porous silica supports. In this study, two head-to-head comparisons were developed to highlight the As(V)-adsorptive ability of meso- and macrostructured silica-based adsorbents. First, the role of the textural properties of a meso-(SBA15) and macrostructured (MOSF) silica support in affecting the structural-morphological features and the adsorption capacity of the active phase (Fe2O3) have been studied. Secondly, a comparison of the arsenic removal ability of inorganic (Fe2O3) and organic (amino groups) active phases was carried out on SBA15. Finally, since silica supports are commonly proposed for both environmental and biomedical applications as active phase carriers, we have investigated secondary silicon and iron pollution. The batch tests at different pH revealed better performance from both Fe2O3-composites at pH 3. The values of qm of 7.9 mg g−1 (53 mg gact−1) and 5.5 mg g−1 (37 mg gact−1) were obtained for SBA15 and MOSF, respectively (gact stands for mass of the active phase). The results suggest that mesostructured materials are more suitable for dispersing active phases as adsorbents for water treatment, due to the obtainment of very small Fe2O3 NPs (about 5 nm). Besides studying the influence of the pore size of SBA15 and MOSF on the adsorption process, the impact of the functionalization was analyzed on SBA15 as the most promising sample for As(V)-removal. The amino-functionalized SBA15 adsorbent (3-aminopropyltriethoxysilane, APTES) exhibited a qm of 12.4 mg g−1 and faster kinetics. Furthermore, issues associated with the release of iron and silicon during the sorption process, causing secondary pollution, were evaluated and critically discussed.
- Published
- 2021
11. Nondestructive characterization of the polycarbonate - octadecylamine interface by surface enhanced Raman spectroscopy
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Valdas Sablinskas, Cordelia Zimmerer, Regine Boldt, Uta Reuter, Andreas Janke, Gediminas Niaura, I. Matulaitiene, and Gerald Steiner
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chemistry.chemical_classification ,Materials science ,Polymers and Plastics ,Organic Chemistry ,02 engineering and technology ,Polymer ,Surface-enhanced Raman spectroscopy ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Characterization (materials science) ,symbols.namesake ,Chemical engineering ,chemistry ,Chemical bond ,visual_art ,symbols ,visual_art.visual_art_medium ,Polycarbonate ,0210 nano-technology ,Spectroscopy ,Raman spectroscopy ,Raman scattering - Abstract
Polymer composite materials are used increasingly in material and engineering science. They provide outstanding mechanical and optical properties. The linkage between the polymer materials is crucial for achieving the desired properties. Understanding the linkage and structure of the polymer-polymer interface layer is a key for utilization polymer composite materials as well as for their fabrication. When analyzing the thin polymer-polymer interface it is important to achieve clear identification of molecular linker structures. One reliable analytical technique allowing this is surface enhanced Raman scattering (SERS) spectroscopy. This study aims at the in-situ evaluation of SERS spectra recorded from the Polycarbonate (PC) –Octadecylamine (ODA) interface to identify the formation of urethane bonds. The detailed analysis of SERS spectra taken before and after the chemical linkage reaction reveals the formation of urethane structures, indicating a chemical bond between PC and ODA. The spectral pattern of urethane groups was identified and evaluated by a reference Raman spectrum.
- Published
- 2019
12. Structure–Property–Processing Relations of Short‐Chain Branched Poly(butylene terephthalate) (PBT) with Biobased Comonomers
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Christian Mielke, Justus Kuhnigk, Doris Pospiech, Hartmut Komber, Regine Boldt, Albena Lederer, Miroslawa El Fray, Tobias Standau, Holger Ruckdäschel, Volker Altstädt, and Brigitte Voit
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Polymers and Plastics ,General Chemical Engineering ,Organic Chemistry ,Materials Chemistry - Published
- 2022
13. Crystal-nuclei formation during injection-molding of poly (l-lactic acid)
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Mengxue Du, Katalee Jariyavidyanont, Regine Boldt, Muhammad Tariq, Matthieu Fischer, Yvonne Spoerer, Ines Kuehnert, and René Androsch
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Polymers and Plastics ,Organic Chemistry ,Materials Chemistry - Published
- 2022
14. Melt-Spun Poly(D,L-lactic acid) Monofilaments Containing N,N-Diethyl-3-methylbenzamide as Mosquito Repellent
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René Androsch, Ignatius Ferreira, Regine Boldt, Harald Brünig, Walter Wilhelm Focke, and Andreas Leuteritz
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Mechanical integrity ,DEET ,02 engineering and technology ,010402 general chemistry ,lcsh:Technology ,01 natural sciences ,Article ,law.invention ,chemistry.chemical_compound ,law ,parasitic diseases ,Organic chemistry ,General Materials Science ,Crystallization ,lcsh:Microscopy ,filaments ,lcsh:QC120-168.85 ,lcsh:QH201-278.5 ,lcsh:T ,fungi ,mosquito repellence ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Amorphous solid ,Lactic acid ,Polyolefin ,Malaria ,chemistry ,Malaria incidence ,melt spinning ,lcsh:TA1-2040 ,lcsh:Descriptive and experimental mechanics ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,poly(lactic acid) ,Melt spinning ,lcsh:Engineering (General). Civil engineering (General) ,0210 nano-technology ,lcsh:TK1-9971 - Abstract
Malaria is still a major tropical disease, with Africa particularly burdened. It has been proposed that outdoor protection could aid substantially in reducing the malaria incidence rate in rural African communities. Recently, melt-spun polyolefin fibers containing mosquito repellents have been shown to be promising materials to this end. In this study, the incorporation of N,N‑Diethyl‑3‑methylbenzamide (DEET)—a popular and widely available mosquito repellent—in commercially available, amorphous poly(D,L-lactic acid) (PDLLA) is investigated with the aim of producing biodegradable mosquito-repelling filaments with a reduced environmental impact. It is shown to be possible to produce macroscopically stable PDLLA-DEET compounds containing up to 20 wt.-% DEET that can be melt-spun to produce filaments, albeit at relatively low take-up speeds. A critical DEET content allows for stress-induced crystallization during the spinning of the otherwise amorphous PDLLA, resulting in the formation of α-crystals. Although the mechanical integrity of the filaments is notably impacted by the incorporation of DEET, these filaments show potential as materials that can be used for Malaria vector control.
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- 2020
15. Fabrication of melt-spun fibers from irradiation modified biocompatible PLA/PCL blends
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Michael Thomas Müller, Regine Boldt, Sven Wießner, Harald Brünig, and Ying Huang
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Fabrication ,Materials science ,Polymers and Plastics ,Organic Chemistry ,General Physics and Astronomy ,Modulus ,Biocompatible material ,Crystallinity ,chemistry.chemical_compound ,chemistry ,Phase (matter) ,Polycaprolactone ,Materials Chemistry ,Irradiation ,Composite material ,Spinning - Abstract
The effect of electron induced reactive processing (EIReP) on the properties of biodegradable polylactide/masticated polycaprolactone (PLA/PCL) blends was firstly investigated without introducing any chemical additives. Subsequently, the melt spinnability of EIReP modified PLA/PCL blends was explored by a piston spinning. Different PCL concentrations (0, 5 and 10 wt%), applied dose (0, 12.5 and 25 kGy) and take up speeds (500 and 2000 m min−1) were evaluated in order to investigate their influences on the fiber morphology, thermal and mechanical properties. SEM investigation indicated that the non-irradiated PLA/PCL fibers demonstrated less uniform diameter. However, the EIReP modification leads to a homogenous fiber diameter distribution hence uniform as-spun fibers can be produced. The crystallinity of PLA phase increased concomitantly with increased PCL contents for all fibers, whereas it slightly reduced by increasing dose. In addition, the crystallinity degree of neat PLA raised from 6.19 to 36.05% by increasing take up speed from 500 to 2000 m min−1. Interestingly, the irradiated PLA/PCL blend fibers with 5 and 10 wt% PCL demonstrated an increased fracture strain of 48.7 and 34.4%, respectively, compared with their non-irradiated fibers. It can be due to the enhanced chain entanglements and interfacial bonding between two phases. However, the irradiated fibers demonstrated similar initial modulus and reduced tenacity compared with the non-irradiated fibers.
- Published
- 2022
16. Novel Concept to Endow Poly(Methyl Methacrylate) Surfaces with Reactive Surface Groups
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Uta Reuter, Lisa Ziegler, Frank Simon, Andreas Janke, Cordelia Zimmerer, and Regine Boldt
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Surface (mathematics) ,chemistry.chemical_classification ,Materials science ,Chemical engineering ,chemistry ,visual_art ,visual_art.visual_art_medium ,General Chemistry ,Polymer ,Thin film ,Poly(methyl methacrylate) - Published
- 2018
17. Process-induced morphology and mechanical properties of high-density polyethylene
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Udo Wagenknecht, Uwe Gohs, Manfred Stamm, and Regine Boldt
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Materials science ,Polymers and Plastics ,Organic Chemistry ,02 engineering and technology ,Polyethylene ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Shear (sheet metal) ,chemistry.chemical_compound ,Rheology ,chemistry ,Transmission electron microscopy ,Ultimate tensile strength ,Materials Chemistry ,Injection moulding ,High-density polyethylene ,Deformation (engineering) ,Composite material ,0210 nano-technology - Abstract
Electron induced reactive processing (EIReP) is an emerging technology for the development of high performance polymer materials. It simultaneously combines the traditional electron beam (EB) treatment of polymers and their melt mixing in the presence of shear stresses and/or rates of deformation. In comparison to traditional EB treatment of high-density polyethylene (HD-PE) at room temperature, EIReP modified HD-PE shows an inhomogeneous morphology, a self-nucleation effect as well as a significant increased tensile strength and decreased elongation at break. In order to identify the reason of these changed properties and the working principle of EIReP, HD-PE has been modified by EB treatment in solid and molten state as well as before and after the presence of shear stresses and/or rates of deformation. Shear stresses and/or rates of deformation were applied during injection moulding of tensile specimens. Based on results of previous work the EB treatments and EIReP of HD-PE were performed under nitrogen atmosphere in order to reduce oxygen induced side reactions. The process induced morphological and mechanical properties have been investigated using optical light microscopy, transmission electron microscopy as well as thermal analysis and tensile tests. Changes of molecular mass were measured with size exclusion chromatography and confirmed by rheological measurements. The results demonstrate that the morphology and specific tensile properties of HD-PE were only changed by an EB treatment before the influence of shear stresses and/or rates of deformation on EB modified HD-PE during injection moulding. In addition, the state of aggregate during EB treatment has no influence on morphology and tensile properties. Consequently, the EIReP induced effect based on electron induced changes of HD-PE molecular structure and the subsequent influence of shear stresses and/or rates of deformation.
- Published
- 2018
18. Pressure- and Temperature-Dependent Crystallization Kinetics of Isotactic Polypropylene under Process Relevant Conditions
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René Androsch, Regine Boldt, Ines Kuehnert, and Yvonne Spoerer
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Polypropylene ,Crystallography ,Materials science ,crystallization kinetic ,General Chemical Engineering ,Comonomer ,Nucleation ,fast scanning chip calorimetry ,Molding (process) ,Condensed Matter Physics ,law.invention ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,QD901-999 ,law ,Tacticity ,Copolymer ,General Materials Science ,Crystallization ,Material properties ,pvT-behavior ,polypropylene - Abstract
In this study, a non-nucleated homopolymer (HP) and random copolymer (RACO), as well as a nucleated HP and heterophasic copolymer (HECO) were investigated regarding their crystallization kinetics. Using pvT-measurements and fast scanning chip calorimetry (FSC), the crystallization behavior was analyzed as a function of pressure, cooling rate and temperature. It is shown that pressure and cooling rate have an opposite influence on the crystallization temperature of the materials. Furthermore, the addition of nucleating agents to the material has a significant effect on the maximum cooling rate at which the formation of α-crystals is still possible. The non-nucleated HP and RACO materials show significant differences that can be related to the sterically hindering effect of the comonomer units of RACO on crystallization, while the nucleated materials HP and HECO show similar crystallization kinetics despite their different structures. The pressure-dependent shift factor of the crystallization temperature is independent of the material. The results contribute to the description of the relationship between the crystallization kinetics of the material and the process parameters influencing the injection-molding induced morphology. This is required to realize process control in injection molding in order to produce pre-defined morphologies and to design material properties.
- Published
- 2021
19. Simultane Abtrennung von Eisen- und Sulfationen durch Kristallisation an Chitosanoberflächen
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Simona Schwarz, Christine Steinbach, Mandy Mende, Dana Schwarz, and Regine Boldt
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Water Science and Technology - Abstract
Als Folgeerscheinung des Bergbaus gelangen sowohl Schwermetallionen als auch verschiedene Anionen, wie Sulfat, Phosphat etc., in die Umwelt und kontaminieren damit Grund- und Oberflächenwässer. Für die Verockerung ist Eisenhydroxid in Form eines rotbraunen Ockerschlamms verantwortlich. Zusätzlich tritt im Spreewald zunehmende Versauerung durch stetig steigende Sulfatbelastung ein. Zur Beseitigung der Rückstände und zur Erhöhung der Wasserqualität können Chitosanpartikel eingesetzt werden. Chitosan ist ein natürlich vorkommendes, ökologisches Biopolymer mit den Eigenschaften eines Superadsorbers. Erstmalig konnten mit Chitosan sowohl Eisenionen als auch Sulfationen gleichzeitig abgetrennt werden. Diese wachsen als Eisensulfat- und Eisenhydroxid-Aggregate auf der Chitosanoberfläche.
- Published
- 2016
20. Simultaneous adsorption of heavy metal ions and anions from aqueous solutions on chitosan—Investigated by spectrophotometry and SEM-EDX analysis
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Mandy Mende, Regine Boldt, Dana Schwarz, Christine Steinbach, and Simona Schwarz
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chemistry.chemical_classification ,Aqueous solution ,Chemistry ,Metal ions in aqueous solution ,chemistry.chemical_element ,Salt (chemistry) ,02 engineering and technology ,010501 environmental sciences ,021001 nanoscience & nanotechnology ,01 natural sciences ,Copper ,Metal ,Chitosan ,Nickel ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Adsorption ,visual_art ,visual_art.visual_art_medium ,Organic chemistry ,0210 nano-technology ,0105 earth and related environmental sciences ,Nuclear chemistry - Abstract
Chitosan (flakes with a degree of deacetylation of 90%) was used as adsorbent for heavy metal ions in solution (copper, iron, nickel). The adsorption capacities were determined in dependence on the adsorption time and the initial metal salt concentration. With increasing adsorption time as well as the initial metal salt concentration the adsorption capacities increased. Highest adsorption capacity was achieved for copper(II)ions with 110 mg/L. Iron(II)- and nickel(II)ions adsorbed with an adsorption capacity of 80 mg/L. The surface of chitosan flakes were investigated before and after the adsorption process by SEM and SEM-EDX, respectively. The formation of crystal-like structures was observed by SEM analysis for the investigation of copper(II)sulfate and iron(II)sulfate. It has been noticed that iron(II)ions oxidized before the adsorption on chitosan occurs. In comparison, the adsorption of nickel salt resulted in a smooth layer on the chitosan surface. SEM-EDX analysis revealed that sulfate adsorbs on the chitosan surface besides the metal cations used.
- Published
- 2016
21. Comparison of transition metal (Fe, Co, Ni, Cu, and Zn) containing tri-metal layered double hydroxides (LDHs) prepared by urea hydrolysis
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Andreas Leuteritz, Sajid Naseem, Regine Boldt, Bianca R. Gevers, and F.J.W.J. Labuschagne
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Thermogravimetric analysis ,Materials science ,Scanning electron microscope ,General Chemical Engineering ,Layered double hydroxides ,02 engineering and technology ,General Chemistry ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Metal ,Transition metal ,visual_art ,engineering ,visual_art.visual_art_medium ,Thermal stability ,Crystallite ,0210 nano-technology ,Powder diffraction ,Nuclear chemistry - Abstract
This paper details a successful synthesis and comparison of a range of tri-metal hydrotalcite-like layered double hydroxides (LDHs) using urea hydrolysis. Transition-metal-substituted MgMAl-LDHs were synthesized with M = Fe, Co, Ni, Cu or Zn. 5 mol% and 10 mol% substitutions were performed, where Mg was substituted with Co, Ni, Cu and Zn, and Al with Fe. The successful synthesis of crystalline MgMAl-LDHs was confirmed using X-ray powder diffraction (XRD) analysis. Energy-dispersive X-ray (EDX) spectroscopy was used to identify substituted metals and determine changes in composition. Changes in morphology were studied using scanning electron microscopy (SEM). Thermogravimetric analysis was used to determine the effect of Fe-, Co-, Ni-, Cu- or Zn-substitution on the thermal degradation of the MgMAl-LDH phase. The structure, morphology and thermal behavior of the LDHs were shown to be influenced by the substituted transition metals. The observed thermal stability took the order MgNiAl- > MgFeAl- = MgAl- ≥ MgCoAl- > MgCuAl- > MgZnAl-LDH. The urea hydrolysis method was shown to be a simple preparation method for well-defined crystallite structures with large hexagonal platelets and good distribution of transition metal atoms in the substituted LDHs.
- Published
- 2018
22. Effect of electron-induced reactive processing on morphology and structural properties of high-density polyethylene
- Author
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Regine Boldt, Manfred Stamm, Uwe Gohs, and Udo Wagenknecht
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chemistry.chemical_classification ,Materials science ,Polymers and Plastics ,Organic Chemistry ,02 engineering and technology ,Polymer ,Polyethylene ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,Crystallinity ,Crystallography ,chemistry.chemical_compound ,Differential scanning calorimetry ,chemistry ,Chemical engineering ,Transmission electron microscopy ,law ,Materials Chemistry ,Irradiation ,High-density polyethylene ,Crystallization ,0210 nano-technology - Abstract
High-density polyethylene (HD-PE) irradiated in the solid state is compared with HD-PE modified by electron-induced reactive processing (EIReP) which combines in a unique set-up the modification of polymers with high energy electrons and melt mixing processes. The effect of these different processes on the morphology and structural properties of HD-PE was investigated with X-ray analysis, differential scanning calorimetry, optical light microscopy combined with a hot stage and transmission electron microscopy as function of applied dose. The increased molecular mass was measured by using gel permeation chromatography and confirmed with rheological measurements. Even though the crystallinity and melting temperatures are constant within the studied range of dose significant differences have been observed in the morphology as well as in the crystallization behaviour. Electron treatment in the solid state causes a shift of crystallization temperature to lower temperatures due to branching and degradation whereas the irradiation under the dynamic conditions of melt mixing leads to higher crystallization temperatures with increased doses due to in-situ self-nucleation. The morphology and crystalline structure of HD-PE is not influenced by an electron treatment in the solid state, but by EIReP. Spatial and thermal stable heterogeneities have been generated only in HD-PE modified with high energy electrons under the dynamic conditions of melt mixing.
- Published
- 2016
23. Chitosan—The Application of a Natural Polymer against Iron Hydroxide Deposition
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Mandy Mende, Regine Boldt, Simona Schwarz, Christine Steinbach, and Dana Schwarz
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chemistry.chemical_classification ,Metal ions in aqueous solution ,Inorganic chemistry ,02 engineering and technology ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Ion ,Chitosan ,Psychiatry and Mental health ,chemistry.chemical_compound ,Adsorption ,chemistry ,Hydroxide ,Deposition (phase transition) ,Sulfate ,0210 nano-technology - Abstract
As a consequence of mining, heavy metal ions can be exposed to the environment hence contaminate ground water and surface water amongst others. The natural polymer chitosan was proved to be an excellent adsorber material for the effective removal of iron and sulfate ions in batch as well as in column experiments. The adsorption behavior of iron ions, as well as sulfate ions was investigated by utilizing chitosan flakes as a natural adsorbent. The removal was studied using adsorbance measurements, SEM and SEM-EDX. The adsorption capacity of chitosan was determined at different times. The received adsorption capacities for iron ions were very promising with a maximum adsorption capacity of 85 mg/g and a rate of separation of 100%. The maximum adsorption capacity obtained for sulfate ions was 188.8 mg/g and a rate of 80%.
- Published
- 2016
24. Improvement of mechanical performance of solution styrene butadiene rubber by controlling the concentration and the size of in situ derived sol–gel silica particles
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Amit Das, Jagannath Chanda, Sven Wießner, Uta Reuter, Klaus Werner Stöckelhuber, V. Sankar Raman, Mikhail Malanin, Subramani Bhagavatheswaran Eshwaran, Andreas Leuteritz, Gert Heinrich, and Regine Boldt
- Subjects
Precipitated silica ,Materials science ,Styrene-butadiene ,General Chemical Engineering ,02 engineering and technology ,General Chemistry ,Dynamic mechanical analysis ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Natural rubber ,visual_art ,Particle-size distribution ,Polymer chemistry ,visual_art.visual_art_medium ,0210 nano-technology ,Fumed silica ,Hydrophobic silica ,Sol-gel - Abstract
Incorporation of precipitated silica rubber compounds is now a standard technology in energy efficient green tire manufacturing process. In the present work silica nanoparticles were generated by an in situ sol–gel technique in solution styrene butadiene rubber (SSBR) using tetraethylorthosilicate (TEOS) as silica precursor. A full control over the amount of silica and size of the silica particles is realized while maintaining a good distribution and dispersion level of the nanosilica particles. In the present case the amount of synthesized silica were varied from 10–50 phr (parts per hundred) and the particles size was found to remain in the range of 200–300 nm. The in situ silica based rubber composites offer better processing characteristics as compared with standard commercial precipitated silica at the same loading level. The reinforcing character of in situ silica was further enhanced by the use of a silane coupling agent, i.e. bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT). Various instrumental techniques, such as tensile test, dynamic mechanical analysis and strain sweep analysis, abrasion test, rebound test and Mooney viscometry reveal superior mechanical performance and good processability of the in situ silica composites. Scanning and transmission electron microscopy studies indicate that the particle size distribution remains in the same range irrespective of the concentration of the silica particles.
- Published
- 2016
25. Fire-safe and environmentally friendly nanocomposites based on layered double hydroxides and ethylene propylene diene elastomer
- Author
-
Debdipta Basu, De-Yi Wang, Amit Das, Jinu Jacob George, Klaus Werner Stöckelhuber, Andreas Leuteritz, Regine Boldt, and Gert Heinrich
- Subjects
Materials science ,EPDM rubber ,General Chemical Engineering ,Vulcanization ,Layered double hydroxides ,02 engineering and technology ,General Chemistry ,Ethylene propylene rubber ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Elastomer ,01 natural sciences ,0104 chemical sciences ,law.invention ,Natural rubber ,law ,visual_art ,Cone calorimeter ,Polymer chemistry ,visual_art.visual_art_medium ,engineering ,Composite material ,0210 nano-technology ,Fire retardant - Abstract
In this work we describe layered double hydroxide (LDH), known as naturally occurring hydrotalcite, based rubber composites that can serve as outstanding fire retardant elastomeric materials. The preparation and detailed characterization of these composites are presented in this study. The inherent slow sulfur cure nature of EPDM rubber is considerably improved by the addition of LDH as realised by the observation of a shortening of the vulcanization time and an improvement of ultimate rheometric torque. This behavior of LDH signifies not only the filler-like character of itself, but also offers vulcanization active surface properties of layered double hydroxide particles. A good rubber–filler interaction was also realised by observing a positive shift of the glass transition temperature of ethylene propylene diene rubber (EPDM) in dynamic mechanical analysis (DMA). The flame retardant property was studied by the cone calorimeter test. The cone calorimeter investigation with sulfur cured gum rubber compounds found a peak heat release rate (PHRR) value of 654 kW m−2. However, at a higher phr loading of Zn–Al LDH i.e., at 40 phr and 100 phr, the PHRR is diminished to 311 kW m−2 and 161 kW m−2, respectively. Thus, this present work can pave the way to fabricate environmentally friendly fire retardant elastomeric composites for various applications.
- Published
- 2016
26. Solubility and Selectivity Effects of the Anion on the Adsorption of Different Heavy Metal Ions onto Chitosan
- Author
-
Christine Steinbach, Regine Boldt, David Vehlow, Dana Schwarz, Martin Müller, Alexander Gündel, Simona Schwarz, and Janek Weißpflog
- Subjects
Metal ions in aqueous solution ,Inorganic chemistry ,heavy metal ions ,Pharmaceutical Science ,chemistry.chemical_element ,Chloride ,Article ,Analytical Chemistry ,lcsh:QD241-441 ,Biopolymers ,Adsorption ,lcsh:Organic chemistry ,Metals, Heavy ,Drug Discovery ,medicine ,Physical and Theoretical Chemistry ,Solubility ,Aqueous solution ,Chemistry ,Organic Chemistry ,Water ,Sorption ,water treatment ,Nickel ,adsorption ,Chemistry (miscellaneous) ,Molecular Medicine ,chitosan ,anions ,Cobalt ,medicine.drug - Abstract
The biopolymer chitosan is a very efficient adsorber material for the removal of heavy metal ions from aqueous solutions. Due to the solubility properties of chitosan it can be used as both a liquid adsorber and a solid flocculant for water treatment reaching outstanding adsorption capacities for a number of heavy metal ions. However, the type of anion corresponding to the investigated heavy metal ions has a strong influence on the adsorption capacity and sorption mechanism on chitosan. In this work, the adsorption capacity of the heavy metal ions manganese, iron, cobalt, nickel, copper, and zinc were investigated in dependence on their corresponding anions sulfate, chloride, and nitrate by batch experiments. The selectivity of the different heavy metal ions was analyzed by column experiments.
- Published
- 2020
27. Investigation of mechanisms for simultaneous adsorption of iron and sulfate ions onto chitosan with formation of orthorhombic structures
- Author
-
Dieter Jehnichen, Janek Weißpflog, Simona Schwarz, Regine Boldt, Benjamin Kohn, Ulrich Scheler, and Vaclav Tyrpekl
- Subjects
Langmuir ,Protonation ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Chitosan ,chemistry.chemical_compound ,Crystallinity ,Colloid and Surface Chemistry ,Adsorption ,chemistry ,Orthorhombic crystal system ,Sulfate ,0210 nano-technology ,Stoichiometry ,Nuclear chemistry - Abstract
The study confirms the interaction of sulfate ions (SO42−) into the polymer chains of chitosan under acidic conditions. As a result the crystallinity of chitosan decreases with (1) increasing protonation of the amino groups and (2) increasing SO42− concentration. The adsorption of iron ions (Fe2+/3+) resulting from (FeSO4)aq onto the chitosan surface takes place incidentally by the oxidative effect of Fe2+/3+ with formation of orthorhombic α-FeOOH and γ-FeOOH. The separation of iron and sulfate ions correlates stoichiometrically. Chitosan with different degrees of deacetylation (DD) were used in order to investigate the influence of DD on the adsorption behavior of iron and sulfate ions. The higher the DD of chitosan, the more iron and sulfate ions can be adsorbed. Langmuir isotherms showed good agreement with the adsorption data obtained (qDD=90 %(Fe) = 2.36 mmol g-1; qDD=90 %(SO42−) = 2.58 mmol g-1). After adsorption process, the adsorber was analyzed extensively via X-ray diffraction, FTIR, 13C-NMR, SEM/EDX measurements and Mossbauer spectroscopy.
- Published
- 2020
28. Complex calcium carbonate/polymer microparticles as carriers for aminoglycoside antibiotics
- Author
-
Stefania Racovita, Adrian Bele, Marcela Mihai, Regine Boldt, Christine Steinbach, Dana Schwarz, Ana-Lavinia Vasiliu, and Simona Schwarz
- Subjects
chemistry.chemical_classification ,General Chemical Engineering ,Aminoglycoside ,Kinetics ,Composite number ,02 engineering and technology ,General Chemistry ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Polyelectrolyte ,0104 chemical sciences ,chemistry.chemical_compound ,Calcium carbonate ,chemistry ,Fourier transform infrared spectroscopy ,0210 nano-technology ,Porosity ,Nuclear chemistry - Abstract
Composite microparticles of CaCO3 and two pectin samples (which differ by the functional group ratio) or corresponding nonstoichiometric polyelectrolyte complexes with different molar ratios (0.5, 0.9 and 1.2) are obtained, characterized and tested for loading and release of streptomycin and kanamycin sulphate. The synthesized carriers were characterized before and after drug loading in terms of morphology (by SEM using secondary electron and energy selective backscattered electron detectors), porosity (by water sorption isotherms) and elemental composition (by elemental mapping using energy dispersive X-ray and FTIR spectroscopy). The kinetics of the release mechanism from the microparticles was investigated using Higuchi and Korsmeyer–Peppas mathematical models.
- Published
- 2018
29. Ultralow percolation threshold in polyamide 6.6/MWCNT composites
- Author
-
Regine Boldt, Liane Häußler, Petra Pötschke, and Beate Krause
- Subjects
Materials science ,Aqueous solution ,Differential scanning calorimetry ,Pulmonary surfactant ,Transmission electron microscopy ,Scanning electron microscope ,Polyamide ,General Engineering ,Ceramics and Composites ,Percolation threshold ,Composite material ,Dispersion (chemistry) - Abstract
When incorporating multiwalled carbon nanotubes (MWCNTs) synthesised by the aerosol-CVD method using different solvents into polyamide 6.6 (PA66) by melt mixing an ultralow electrical percolation threshold of 0.04 wt.% was found. This very low threshold was assigned to the specific characteristic of the MWCNTs for which a very high aspect ratio, a good dispersability in aqueous surfactant dispersions, and relatively low oxygen content near the surface were measured. The investigation of the composites by transmission electron microscopy on ultrathin cuts as well as by scanning electron microscopy combined with charge contrast imaging on compression moulded plates illustrated a good MWCNT dispersion within the PA66 matrix and that the very high aspect ratio of the nanotubes remained even after melt processing. Additionally, the thermal behaviour of the PA66 composites was investigated using differential scanning calorimetry (DSC) showing that the addition of only 0.05 wt.% MWCNT leads to an increase of the onset crystallization temperature of 11 K.
- Published
- 2015
30. A multidisciplinary approach to understanding of structure-property correlations in polyamide-layered silicate nanocomposites: Expectations and challenges
- Author
-
Regine Boldt, Tayebeh Sadat Kermaniyan, Mohammad Reza Saeb, and Hamid Garmabi
- Subjects
Marketing ,Materials science ,Nanocomposite ,Polymers and Plastics ,General Chemical Engineering ,Modulus ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Exfoliation joint ,Silicate ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Rheology ,Ultimate tensile strength ,Materials Chemistry ,Composite material ,0210 nano-technology ,Dispersion (chemistry) - Abstract
Layered silicate-incorporated polyamide 6 (PA6) nanocomposites were studied to undertake correlations between morphological, rheological, permeability, and mechanical characteristics. The microstructure of nanocomposite specimens was seen through X-ray diffraction, atomic force microscopy, and transmission electron microscopy measurements. In addition, impact, tensile, and permeability data were analyzed combining the theoretical and experimental analyses to draw a convincing conclusion on the state of exfoliation and intercalation of layered silicates throughout the PA6 matrix. The results provided support for the fact that introduction of silicate nanofiller brings about some advantages like higher impact and modulus, at the same time some drawbacks arising from the improper dispersion of nanoplatelets. It was also revealed that microscopic studies do not necessarily agree with each other regarding filler dispersion state. The correlations between microstructure and experimental data from mechanical and permeability tests were checked by some well-established theoretical models. The trends in the test results were somewhat dependent on the state of filler dispersion. The role of the crystalline areas in achieving higher permeability resistance was also discussed, in a short review, to be comprehensively discussed in a future work. J. VINYL ADDIT. TECHNOL., 2015. © 2015 Society of Plastics Engineers
- Published
- 2015
31. Preparation of melt-spun antimicrobially modified LDH/polyolefin nanocomposite fibers
- Author
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Percy Schröttner, Gert Heinrich, Regine Boldt, Andreas Leuteritz, Burak Kutlu, and Enno Jacobs
- Subjects
Materials science ,Camphorsulfonic acid ,Gram-positive bacteria ,Proteus vulgaris ,Bioengineering ,Microbial Sensitivity Tests ,Gram-Positive Bacteria ,Nanocomposites ,Biomaterials ,chemistry.chemical_compound ,Anti-Infective Agents ,Ciprofloxacin ,Staphylococcus epidermidis ,Gram-Negative Bacteria ,Polymer chemistry ,Hydroxides ,Magnesium ,biology ,biology.organism_classification ,Antimicrobial ,chemistry ,Polyethylene ,Mechanics of Materials ,Hydroxide ,Enterobacter cloacae ,Bacteria ,Aluminum ,Nuclear chemistry - Abstract
Layered double hydroxide (LDH) was synthesized and organically modified with camphorsulfonic acid (CSA) and ciprofloxacin. The thermal stability of CSA was improved remarkably under LDH shielding. A minimal inhibitory concentration of free CSA against tested bacteria was determined in order to define the essential quantity in LDH modification. The modified LDHs were melt-compounded with high density polyethylene and the prepared nanocomposites were further melt-spun using a piston-type spinning device. The melt-spun fibers were tested for their antimicrobial activity against Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa, Enterobacter cloacae, Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus pyogenes. CSA integrated fibers show susceptibility against Gram-positive bacteria and ciprofloxacin integrated fibers showed activity against both Gram-positive and Gram-negative bacteria.
- Published
- 2014
32. A combinatorial approach to evaluation of monomer conversion and particle size distribution in vinyl chloride emulsion polymerization
- Author
-
Regine Boldt, Hossein Abedini, Mohammad Reza Saeb, Amir Saeid Pakdel, and Hossein Ali Khonakdar
- Subjects
education.field_of_study ,Materials science ,Polymers and Plastics ,Bulk polymerization ,Population ,Nucleation ,Emulsion polymerization ,General Chemistry ,Condensed Matter Physics ,Vinyl chloride ,chemistry.chemical_compound ,Monomer ,chemistry ,Chemical engineering ,Polymerization ,Particle-size distribution ,Polymer chemistry ,Materials Chemistry ,education - Abstract
This work is targeted to study emulsion polymerization of vinyl chloride monomer (VCM) using experimental and mathematical methods. To fulfill this goal, a computer code was developed on the basis of zero–one population balance by which the effects of initiator and emulsifier concentration on the evolution of VCM conversion were investigated in the course of polymerization. The model was also trained to capture the coagulation of the particles. This enabled to adopt a reliable way of evaluating the particle size distribution (PSD). In particular, the rates of homogeneous and micellar nucleation mechanisms were simulated and reasonably predicted alterations in the PSD and the number of polymer particles under the influence of aforementioned parameters. The results from modeling were satisfactorily consistent with the experimental outputs and obviously visualized the impact of initiator and surfactant concentration on the PSD of the prepared PVC latexes.
- Published
- 2014
33. Localization of carbon nanotubes in polyamide 6 blends with non-reactive and reactive rubber
- Author
-
Cecile Schneider, Martin Weber, Regine Boldt, Beate Krause, Hye Jin Park, and Petra Pötschke
- Subjects
chemistry.chemical_classification ,Thermoplastic ,Materials science ,Polymers and Plastics ,Organic Chemistry ,Maleic anhydride ,Carbon nanotube ,Polymer ,law.invention ,chemistry.chemical_compound ,chemistry ,Natural rubber ,law ,visual_art ,Phase (matter) ,Polyamide ,Materials Chemistry ,visual_art.visual_art_medium ,Electrical measurements ,Composite material - Abstract
Blending of two immiscible polymer matrices can be an effective way to combine favourable properties of both blend partners. The additional incorporation of multiwalled carbon nanotubes (MWCNTs) in such thermoplastic blends may further enhance the blend properties and especially generate electrical conductivity. In the present study, 20 wt.% of non-reactive rubber and maleic anhydride functionalized rubber were melt blended with polyamide 6 and 3 wt.% MWCNTs by using different incorporation strategies. For the blends containing non-reactive rubber, the MWCNTs were always localized selectively in the thermodynamically preferred polyamide phase as shown by TEM images and electrical measurements. Interestingly, the different strategies resulted in different localization behaviours of the MWCNTs in case of the reactive rubber. These findings demonstrate the significant influence of maleic anhydride groups of the rubber component on localization of MWCNTs in the different blend phases which results in different values of electrical volume resistivity of the blends.
- Published
- 2014
34. Effects of LDH synthesis and modification on the exfoliation and introduction of a robust anion-exchange procedure
- Author
-
Andreas Leuteritz, Regine Boldt, Burak Kutlu, Gert Heinrich, and Dieter Jehnichen
- Subjects
Materials science ,Nanocomposite ,Polymer nanocomposite ,Ion exchange ,General Chemical Engineering ,Intercalation (chemistry) ,Inorganic chemistry ,Layered double hydroxides ,General Chemistry ,engineering.material ,Exfoliation joint ,Small molecule ,Industrial and Manufacturing Engineering ,Functional importance ,engineering ,Environmental Chemistry - Abstract
Layered double hydroxides (LDHs) were synthesized and modified with different methods and also with different functional molecules. An easy and successful one-pot anion-exchange intercalation procedure was introduced and the influencing parameters of the modification were investigated in comparison to other modification methods. LDH based polymer nanocomposites were prepared with a microcompounder using melt-mixing method. The exfoliation behavior of organomodified LDHs was investigated with two different rheological models and visualized with electron microscopy techniques. Some of the relations between modification of LDH and the extent of exfoliation were identified. Highly exfoliated nanocomposites were successfully prepared after intercalation even with a small molecule like hexanesulfonic acid by performing the introduced anion exchange method.
- Published
- 2014
35. Nano-scale morphological analysis of graphene–rubber composites using 3D transmission electron microscopy
- Author
-
René Jurk, Amit Das, Dieter Fischer, Dieter Jehnichen, Gert Heinrich, Regine Boldt, and Klaus Werner Stöckelhuber
- Subjects
Styrene-butadiene ,Materials science ,Graphene ,General Chemical Engineering ,General Chemistry ,Carbon black ,Exfoliation joint ,law.invention ,symbols.namesake ,chemistry.chemical_compound ,Natural rubber ,chemistry ,Transmission electron microscopy ,law ,visual_art ,symbols ,visual_art.visual_art_medium ,Composite material ,Raman spectroscopy ,Nanoscopic scale - Abstract
In this work three-dimensional transmission electron microscopy (3D-TEM) is exploited to characterize a soft graphene based nano-composites structure and the constituted morphology in a qualitative way. The reconstruction of the two dimensional slides into a three dimensional tomographic image is a powerful tool, when the images of the nano-object are reflected into a quasi-distinguishable object due to superposition effect. By using this technique it is possible to mark the contour area of the nano-sized object inside the soft rubber matrix. To extract information about the filler network, the clustering process of the fillers or the existence of single or multiple graphene sheets, a solution polymerised styrene butadiene rubber was selected as a soft matrix which was filled with carbon black (CB) and graphene nano-platelets (GnP). The dispersion/exfoliation of the stacked graphene sheets into individual single sheets was facilitated by the presence of carbon black in the system as understood from TEM, X-ray diffraction and Raman spectroscopic studies. The existence of oligo-layer graphene sheets was detected by this 3D-TEM, especially when the rubber matrix exists in a complex morphology arisen from filler–filler networks in all spatial dimensions.
- Published
- 2014
36. Location of dispersing agent in rubber nanocomposites during mixing process
- Author
-
Gert Heinrich, H.-J. Radusch, Klaus Werner Stöckelhuber, Sven Wießner, H. H. Le, K. Oßwald, Gaurav K. Gupta, Regine Boldt, and Amit Das
- Subjects
chemistry.chemical_classification ,Filler (packaging) ,Materials science ,Polymers and Plastics ,Organic Chemistry ,Carbon nanotube ,Polymer ,Dispersant ,Surface energy ,law.invention ,chemistry.chemical_compound ,chemistry ,Natural rubber ,law ,visual_art ,Ionic liquid ,Materials Chemistry ,visual_art.visual_art_medium ,Wetting ,Composite material - Abstract
In the present work, the development of morphology and selective wetting of nanoclay and carbon nanotubes (CNTs) in rubber nanocomposites were characterized qualitatively by means of the optical microscopy, TEM and AFM and quantitatively by means of the wetting concept . Carboxylated hydrogenated nitrile butadiene rubber (XHNBR), ionic liquid and ethanol were used as dispersing agent and they show very good effect on the macro- and microdispersion of nanofillers in different rubbers. It was found that the selective wetting of filler surface by the dispersing agent and rubber matrix is controlled by thermodynamic and kinetic factors. A model basing on surface energy data of polymer components (rubber and dispersing agent) and filler was introduced in order to determine the thermodynamic equilibrium state of filler wetting, which is found to be simultaneously determined by the filler–polymer affinity and the rubber/dispersing agent mass ratio. During the mixing process a replacement process of bound polymer components takes place on the filler surface until the predicted state is reached.
- Published
- 2013
37. Shear-induced shish-kebab structures in isotactic polypropylene using acicular precipitated calcium carbonate as whisker
- Author
-
Marijan Vucak, Roland Vogel, Regine Boldt, and Liane Häußler
- Subjects
Polypropylene ,Acicular ,Materials science ,Polymers and Plastics ,Monocrystalline whisker ,Whiskers ,General Chemistry ,law.invention ,chemistry.chemical_compound ,chemistry ,Whisker ,law ,Shish kebab ,Materials Chemistry ,Composite material ,Crystallization ,Tensile testing - Abstract
It has been reported in the technical literature that whiskers of rodlike single crystals can be used in order to generate shish-kebab structures or other different lamellae morphologies during isothermal or dynamic crystallization of sheared or presheared polymer melts. The expected advantage of the changed crystalline structure is a reinforcing effect of the composite. A lot of papers reported about the application of inorganic and organic whiskers such as cellulose and chitin whiskers. This study reports on an attempt to use acicular PCC as appropriate whisker for improving mechanical properties of polypropylene. In this article special attention is given to demonstrate the effect of flow induced crystallization under varying shear conditions in order to improve the mechanical properties. The effects were demonstrated using rheology, thermal analysis, tensile testing, and transmission electron microscopy. POLYM. ENG. SCI., 54:2057–2063, 2014. © 2013 Society of Plastics Engineers
- Published
- 2013
38. Influence of processing on morphology in short aramid fiber reinforced elastomer compounds
- Author
-
Gert Heinrich, Regine Boldt, Sven Wiessner, and Christian Hintze
- Subjects
Materials science ,Polymers and Plastics ,Composite number ,General Chemistry ,Raw material ,Elastomer ,Aspect ratio (image) ,Durability ,Surfaces, Coatings and Films ,Aramid ,Natural rubber ,visual_art ,Materials Chemistry ,visual_art.visual_art_medium ,Fiber ,Composite material - Abstract
The rubber industry is nowadays facing the general increase of raw materials as the customers are confronted with rising prices for energy. Therefore there is a need for higher durability of elastomer applications. Short fiber reinforced elastomers can contribute to the improvement of dynamic and wear properties. To determine structure–property relationships in short fiber reinforced elastomer compounds it is of crucial interest to know the contributions of fiber aspect ratio, volume content, orientation and fiber–elastomer interaction. Therefore the influence of different processing conditions and fiber contents on the resulting morphology and macroscopic properties was investigated in this article by the help of fluorescence and confocal laser microscopy using a transparent ethylene-propylene-diene rubber (EPDM) matrix. It was found that the processing induced fiber breakage was the key factor in determining the composite morphology and subsequent physical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1682–1690, 2013
- Published
- 2013
39. Tuning the processability, morphology and biodegradability of clay incorporated PLA/LLDPE blends via selective localization of nanoclay induced by melt mixing sequence
- Author
-
Seyed Hassan Jafari, Gert Heinrich, Udo Wagenknecht, Regine Boldt, Ladan As'habi, and Hossein Ali Khonakdar
- Subjects
Nanocomposite ,Melt mixing ,Materials science ,Polymers and Plastics ,General Chemical Engineering ,Organic Chemistry ,Mixing methods ,Twin screw extruder ,One-Step ,Biodegradation ,lcsh:Chemical technology ,Biodegradable polymers ,Polylactic acid ,Nanocomposites ,Linear low-density polyethylene ,chemistry.chemical_compound ,chemistry ,Rheology ,lcsh:TA401-492 ,Materials Chemistry ,lcsh:Materials of engineering and construction. Mechanics of materials ,lcsh:TP1-1185 ,Physical and Theoretical Chemistry ,Composite material - Abstract
Polylactic acid (PLA)/linear low density polyethylene (LLDPE) blend nanocomposites based on two different commercial-grade nanoclays, Cloisite® 30B and Cloisite® 15A, were produced via different melt mixing procedures in a counter-rotating twin screw extruder. The effects of mixing sequence and clay type on morphological and rheological behaviors as well as degradation properties of the blends were investigated. The X-ray diffraction (XRD) results showed that generally the level of exfoliation in 30B based nanocomposites was better than 15A based nanocomposites. In addition, due to difference in hydrophilicity and kind of modifiers in these two clays, the effect of 30B on refinement of dispersed phase and enhancement of biodegradability of PLA/LLDPE blend was much more remarkable than that of 15A nanoclay. Unlike the one step mixing process, preparation of nanocomposites via a two steps mixing process improved the morphology. Based on the XRD and TEM (transmission electron microscopic) results, it is found that the mixing sequence has a remarkable influence on dispersion and localization of the major part of 30B nanoclay in the PLA matrix. Owing to the induced selective localization of nanoclays in PLA phase, the nanocomposites prepared through a two steps mixing sequence exhibited extraordinary biodegradability, refiner morphology and better melt elasticity.
- Published
- 2013
40. Rubber composites based on graphene nanoplatelets, expanded graphite, carbon nanotubes and their combination: A comparative study
- Author
-
René Jurk, Klaus Werner Stöckelhuber, Dieter Fischer, Gaurav R. Kasaliwal, Regine Boldt, Amit Das, and Gert Heinrich
- Subjects
Materials science ,Styrene-butadiene ,Composite number ,General Engineering ,Dynamic mechanical analysis ,engineering.material ,chemistry.chemical_compound ,chemistry ,Natural rubber ,Percolation ,Filler (materials) ,visual_art ,Ceramics and Composites ,engineering ,visual_art.visual_art_medium ,Graphite ,Composite material ,Tensile testing - Abstract
Solution styrene butadiene rubber (S-SBR) composites reinforced with graphene nanoplatelets (GnPs), expanded graphite (EG), and multiwalled carbon nanotubes (MWCNTs) were prepared and the electrical and various mechanical properties were compared to understand the specific dispersion and reinforcement behaviours of these nanostructured fillers. The electrical resistivity of the rubber composite gradually decreased with the increase of filler amount in the composite. The electrical percolation behaviour was found to be started at 15 phr (parts per hundred rubber) for GnP and 20 phr for EG filled systems, whereas a sharp drop was found at 5 phr for MWCNT based composites. At a particular filler loading, dynamic mechanical analysis and tensile test showed a significant improvement of the mechanical properties of the composites comprised of MWCNT followed by GnP and then EG. The high aspect ratio of MWCNT enabled to form a network at low filler loading and, consequently, a good reinforcement effect was observed. To investigate the effect of hybrid fillers, MWCNT (up to 5 phr) were added in a selected composition of EG based compounds. The formation of a mixed filler network showed a synergistic effect on the improvement of electrical as well as various mechanical properties.
- Published
- 2012
41. Process induced morphology of irradiated HD-PE
- Author
-
Manfred Stamm, Regine Boldt, Gert Heinrich, and Uwe Gohs
- Subjects
chemistry.chemical_classification ,Work (thermodynamics) ,Morphology (linguistics) ,Materials science ,Electron ,Polymer ,Polyethylene ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Polymer chemistry ,High-density polyethylene ,Irradiation ,Material properties - Abstract
The preparation of cross-linked polyethylene with high energy electrons is a well-known and used method to change material properties [1-6]. A new developed technique called “Electron induced reactive processing” simultaneously combines polymer modification with high energy electrons and melt mixing processes [7-13]. In the case of polyethylene, this novel technique leads to exceptional mechanical properties. Definitely, these properties depend on the molecular architecture as well as the morphological characteristics of polyethylene after the electron treatment.In this work we concentrate on the morphological changes of high density polyethylene generated by using state of the art high energy electron treatment in the solid state compared with high density polyethylene modified with the electron induced reactive processing.
- Published
- 2016
42. Kinetics of filler wetting and dispersion in carbon nanotube/rubber composites
- Author
-
Rameshwar Adhikari, H. H. Le, K. W. Stoeckelhuber, Regine Boldt, X.T. Hoang, H.-J. Radusch, Amit Das, Uwe Gohs, and Gert Heinrich
- Subjects
chemistry.chemical_classification ,Materials science ,General Chemistry ,Polymer ,Carbon nanotube ,Conductivity ,law.invention ,chemistry ,Natural rubber ,law ,Electrical resistivity and conductivity ,visual_art ,visual_art.visual_art_medium ,Surface modification ,General Materials Science ,Wetting ,Composite material ,Curing (chemistry) - Abstract
The effects of the surface modification of multi-walled carbon nanotubes (MWCNTs) by an ionic liquid, 1-butyl 3-methyl imidazolium bis(trifluoromethyl-sulphonyl)imide (BMI) on the kinetics of filler wetting and dispersion as well as resulting electrical conductivity of polychloroprene (CR) composites were studied. Two different MWCNTs were used, Baytubes and Nanocyl, which differ in their structure, purity and compatibility to CR and BMI. The results showed that BMI can significantly improve the macrodispersion of Baytubes, and increases the electrical conductivity of the uncured BMI–Baytube/CR composites up to five orders of magnitude. In contrast, the use of BMI slows the dispersion process and the development of conductivity of BMI–Nanocyl/CR composites. Our wetting concept was further developed for the quantification of the bound polymer on the CNT surface. We found that the bonded BMI on the CNT surface is replaced by the CR molecules during mixing as a result of the concentration compensation effect. The de- and re-agglomeration processes of CNTs taking place during the subsequent curing process can increase or decrease the electrical conductivity significantly. The extent of the conductivity changes is strongly determined by the composition of the bound polymer and the curing technique used.
- Published
- 2012
43. Method for Simultaneously Improving the Thermal Stability and Mechanical Properties of Poly(lactic acid): Effect of High-Energy Electrons on the Morphological, Mechanical, and Thermal Properties of PLA/MMT Nanocomposites
- Author
-
Gert Heinrich, Nian-Jun Kang, Uwe Gohs, De-Yi Wang, Regine Boldt, Udo Wagenknecht, and Andreas Leuteritz
- Subjects
chemistry.chemical_classification ,Nanocomposite ,Materials science ,Surfaces and Interfaces ,Polymer ,Condensed Matter Physics ,chemistry.chemical_compound ,Montmorillonite ,chemistry ,Chemical engineering ,Transmission electron microscopy ,Ultimate tensile strength ,Polymer chemistry ,Electrochemistry ,General Materials Science ,Thermal stability ,Irradiation ,Elongation ,Spectroscopy - Abstract
Nanocomposites derived from poly(lactic acid) (PLA) and organically modified montmorillonite (oMMT) have been cross-linked by high-energy electrons in the presence of triallyl cyanurate (TAC). The morphology of untreated and cross-linked PLA/MMT nanocomposites was characterized by wide-angle X-ray scattering (WAXS) and transmission electron microscopy (TEM). This treatment can improve both the thermal stability and the glass-transition temperatures of the PLA nanocomposites (e.g., PLA-MMT-TAC 30kGy, 50kGy, and 70kGy) because of the formation of cross-linking structures in the nanocomposites that will considerably reduce the mobility of polymers. Interestingly, at relatively low irradiation doses (e.g., 30 and 50 kGy) a good balance between tensile strength and elongation at break for the PLA nanocomposites could be achieved. These mechanical properties are superior to those of pure PLA. Therefore, combining nanotechnology and electron beam cross-linking is a promising new method of simultaneously improving the mechanical properties (toughness and tensile strength) and thermal stability of PLA.
- Published
- 2012
44. Semimetallic Paramagnetic Nano-Bi2Ir and Superconducting Ferromagnetic Nano-Bi3Ni by Microwave-Assisted Synthesis and Room Temperature Pseudomorphosis
- Author
-
R. Skrotzki, Thomas Herrmannsdörfer, Martin Heise, Joachim Wosnitza, Anett Grigas, Daniel Köhler, Regine Boldt, Stefan Kaskel, Anna Isaeva, and Michael Ruck
- Subjects
Inorganic Chemistry ,Magnetization ,Paramagnetism ,Condensed matter physics ,Chemistry ,Rietveld refinement ,Diamagnetism ,Curie temperature ,Saturation (magnetic) ,Magnetic susceptibility ,Critical field - Abstract
Uniform nanocrystals of the intermetallic compounds Bi2Ir (diameter ≥ 50 nm) and Bi3Ni (typical size 200 × 600 nm) were obtained by a microwave-assisted polyol process at 240 °C. The method was also applied to the spatially confined reaction environment in the microporous exo-template SBA-15 resulting in Bi3Ni particles of about 6 nm. Non-crystalline bundles of parallel Bi3Ni nanofibres that have an individual diameter of less than 1 nm were obtained by reductive pseudomorphosis of the subiodide Bi12Ni4I3 at room temperature. Magnetic susceptibility measurements demonstrate coexistence of ferromagnetism and superconductivity in a single phase for the nanostructured Bi3Ni materials. Curie temperature, coercive field, remnant magnetization, saturation moment, diamagnetic screening, and critical field vary with particle size. The crystal structure of Bi2Ir was determined by Rietveld refinement of powder X-ray diffraction data. Bi2Ir crystallizes in the monoclinic arsenopyrite type (space group P21/c), a superstructure of the markasite type, with a = 690.11(1), b = 678.85(1), c = 696.17(1) pm, and β = 116.454(1)°. In contrast to most of the other phases of this type, the Bi2Ir is not a diamagnetic semiconductor but a weakly paramagnetic semimetal. Conductivity measurements down to 4 K and magnetization measurements in a field of μ0H = 10 mT down to 1.8 K give no evidence for a transition into the superconducting state. Bonding analysis shows prevailing contribution of Bi–Bi interactions to the conduction, whereas Bi–Ir bonding is mostly covalent and localized.
- Published
- 2012
45. Effect of end-capped nanosilica on mechanical properties and microstructure of LLLDPE/EVA blends
- Author
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Udo Wagenknecht, Seyed Hassan Jafari, Mahmud Heidary, Regine Boldt, Gert Heinrich, and Hossein Ali Khonakdar
- Subjects
chemistry.chemical_classification ,Nanocomposite ,Materials science ,Polymers and Plastics ,Ethylene-vinyl acetate ,General Chemistry ,Polymer ,Polyethylene ,Microstructure ,Surfaces, Coatings and Films ,Linear low-density polyethylene ,chemistry.chemical_compound ,chemistry ,Ultimate tensile strength ,Materials Chemistry ,Copolymer ,Composite material - Abstract
This article describes the influence of a hexamethyldisilane-treated nanosilica (end-capped SiO2) on morphological and tensile properties of linear low-density polyethylene (LLDPE)/ethylene vinyl acetate copolymer (EVA) blends prepared by one step melt mixing process via a twin screw extruder. The treatment replaces many of the surface hydroxyl groups on the nanosilica with extremely hydrophobic trimethylsilyl groups. Transmission electron microscopic results revealed that the treated nanosilica formed small aggregates in polymer matrix and they were mostly localized in the LLDPE matrix besides localizing in EVA droplets and at LLDPE/EVA interface. These nanoparticles had compatibilizing role on the blend system and at high content changed morphology from biphasic toward a monophasic. Addition of the end-capped nanosilica to the blend and increasing its content increased the Young's modulus, tensile strength as well as elongation at break of the nanocomposites. Different models were used to predict the Young's modulus of the nanocomposites. It was found that the experimental data were better fitted by Counto model than the other models. Melt rheological investigations on the nanosilica filled LLDPE/EVA blend system showed that incorporation of the treated nanosilica, even up to 10 wt %, did not lead to a solid-like behavior at low-frequency indicating ease of processing of such highly filled system. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
- Published
- 2012
46. Methoden zur Charakterisierung der Dispergierbarkeit und Längenanalyse von Carbon Nanotubes
- Author
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Petra Poetschke, Beate Krause, Mandy Mende, Gudrun Petzold, and Regine Boldt
- Subjects
chemistry.chemical_classification ,Morphology (linguistics) ,Materials science ,General Chemical Engineering ,Nanoparticle ,General Chemistry ,Polymer ,Carbon nanotube ,Industrial and Manufacturing Engineering ,law.invention ,chemistry ,Chemical engineering ,law ,Compounding ,Dispersion (optics) ,Length distribution - Published
- 2012
47. The influence of matrix viscosity on MWCNT dispersion and electrical properties in different thermoplastic nanocomposites
- Author
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Michael Thomas Müller, Regine Boldt, Robert Socher, Petra Pötschke, and Beate Krause
- Subjects
Nanocomposite ,Materials science ,Polymers and Plastics ,Organic Chemistry ,Percolation threshold ,Physics::Fluid Dynamics ,Polybutylene terephthalate ,chemistry.chemical_compound ,Low-density polyethylene ,Viscosity ,chemistry ,visual_art ,Materials Chemistry ,visual_art.visual_art_medium ,Composite material ,Polycarbonate ,Reduced viscosity ,Dispersion (chemistry) - Abstract
Composites of MWCNTs having each three different levels of matrix viscosity with five different polymers (polyamide 12, polybutylene terephthalate, polycarbonate, polyetheretherketone and low density polyethylene) were melt mixed to identify the general influence of matrix viscosity on the electrical properties and the state of MWCNT dispersion. Huge differences in the electrical percolation thresholds were found using the same polymer matrix with different viscosity grades. The lowest percolation thresholds were always found in the composites based on the low viscosity matrix. The state of primary MWCNT agglomerate dispersion increased with increasing matrix viscosity due to the higher input of mixing energy. TEM investigations showed nanoagglomerated structures in the low viscosity samples which are obviously needed to achieve low resistivity values. The effect of nanotube shortening was quantified using two different viscosity grades of polycarbonate. Due to the higher mixing energy input the nanotube shortening was more pronounced in the high viscosity matrix which partially explains the higher percolation threshold.
- Published
- 2012
48. Percolation behaviour of multiwalled carbon nanotubes of altered length and primary agglomerate morphology in melt mixed isotactic polypropylene-based composites
- Author
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Bernd Kretzschmar, Beate Krause, Roland Weidisch, Regine Boldt, Katharina Menzer, and Petra Pötschke
- Subjects
Nanotube ,Materials science ,Composite number ,General Engineering ,Maleic anhydride ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Rheology ,chemistry ,Agglomerate ,Macroscopic scale ,Tacticity ,Ceramics and Composites ,Composite material ,Ball mill - Abstract
The effect of ball milling on the structural characteristics and further on the dispersion and percolation behaviour of multiwalled carbon nanotubes (MWCNTs) in melt mixed composites using a maleic anhydride modified isotactic polypropylene as matrix was investigated. TEM and SEM revealed that ball milled nanotubes were considerably shorter and showed a compact primary agglomerate morphology compared to the as-synthesised MWCNTs. At macro scale ball milled MWCNTs were found to be better dispersed, whereas at sub-micron scale the states of dispersion of both nanotube materials were comparable. The differences in the composite morphologies as well as in the composites electrical and rheological percolation behaviour were assigned to the altered MWCNT structure due to ball milling treatment. The dispersibility of ball milled MWCNTs was restricted due to their more compact agglomerate morphology. Furthermore, the ability to form percolated network structures was restrained by their shorter length and, again, their compact primary agglomerates. An effective agglomerate interaction radius depending on the nanotube structural characteristics, length and agglomerate morphology, is suggested in order to explain the experimental findings.
- Published
- 2011
49. Influence of dry grinding in a ball mill on the length of multiwalled carbon nanotubes and their dispersion and percolation behaviour in melt mixed polycarbonate composites
- Author
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Mandy Mende, Regine Boldt, Gudrun Petzold, Petra Pötschke, Tobias Villmow, Beate Krause, Leibniz-Institut für Polymerforschung Dresden e.V. (IPF), and Leibniz Association
- Subjects
Nanotube ,Materials science ,A. Carbon nanotubes ,General Engineering ,Percolation threshold ,Carbon nanotube ,Dispersion ,[SPI.MAT]Engineering Sciences [physics]/Materials ,law.invention ,A. Polymer-matrix composites (PMCs) ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,chemistry ,Agglomerate ,law ,visual_art ,Nano ,Masterbatch ,D. Transmission electron microscopy (TEM) ,Ceramics and Composites ,visual_art.visual_art_medium ,B. Electrical properties ,Polycarbonate ,Composite material ,Ball mill - Abstract
International audience; Ball milling of carbon nanotubes (CNTs) in the dry state is a common way to produce tailored CNT materials for composite applications, especially to adjust nanotube lengths. For Nanocyl NC7000 nanotube material before and after milling for 5 and 10 hours the length distributions were quantified using TEM analysis, showing decreases of the mean length to 54 and 35%, respectively. With increasing ball milling time in addition a decrease of agglomerate size and an increase of packing density took place resulting in a worse dispersability in aqueous surfactant solutions. In melt mixed CNT polycarbonate composites produced using masterbatch dilution step the electrical properties, the nanotube length distribution after processing, and the nano- and macrodispersion of the nanotubes were studied. The slight increase in the electrical percolation threshold in the melt mixed composites with ball milling time of CNTs can be assigned to lower nanotubes lengths as well as the worse dispersability of the ball milled nanotubes. After melt compounding, the mean CNT lengths were shortened to 31%, 50%, and 66% of the initial lengths of NC7000, NC7000-5h, and NC7000-10h, respectively.
- Published
- 2011
50. A method for determination of length distributions of multiwalled carbon nanotubes before and after melt processing
- Author
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Regine Boldt, Petra Pötschke, and Beate Krause
- Subjects
Nanotube ,Materials science ,General Chemistry ,Carbon nanotube ,Multiwalled carbon ,law.invention ,Matrix (chemical analysis) ,Solvent ,law ,Transmission electron microscopy ,visual_art ,visual_art.visual_art_medium ,General Materials Science ,Length distribution ,Composite material ,Polycarbonate - Abstract
A relatively simple method to determine the length distribution of carbon nanotubes (CNTs) before and after melt processing was developed. This involves the selection of a suitable solvent for dispersing pristine CNTs as well as to dissolve the matrix of melt mixed composites and the choice of an appropriate nanotube concentration. The length of suitably individualized CNTs was visualized using transmission electron microscopy and length distributions were measured using image analysis. Examples are shown for Baytubes® C150HP and Nanocyl™ NC7000 and their melt mixed composites with polycarbonate where the same procedure was applied to both, measuring the initial length distribution and the distribution after recovering from the composites. These results indicated a significant shortening after melt processing up to 30% of the initial length.
- Published
- 2011
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