Claus Wrana - Academia.edu (original) (raw)
Papers by Claus Wrana
Chemie in Unserer Zeit, Dec 1, 2009
Synthetische Kautschuke losen immer mehr Aufgaben, in denen Elastizitat gefragt, Naturkautschuk a... more Synthetische Kautschuke losen immer mehr Aufgaben, in denen Elastizitat gefragt, Naturkautschuk auf Grund seiner Empfindlichkeit gegenuber UV-Licht, Ozon und Hitze aber uberfordert ist: Uber die Halfte der heute verbrauchten Kautschuke stammen aus den Reaktoren der Chemischen Industrie. Synthesekautschuke sind ihrem naturlichen “Vorbild” nicht nur in Sachen Alterungs- und Chemikalienbestandigkeit uberlegen: Sie konnen auserst effektiv an immer neue Anforderungen angepasst werden – etwa durch Variation ihrer Zusammensetzung und Molekularchitektur, durch Einsatz neuer Katalysatoren und Produktionsverfahren und nachtragliche Modifikation des Polymers. Diese Entwicklungsarbeiten erfordern ein vertieftes Verstandnis der Gummichemie und -Physik. Synthetic rubbers help to solve severe problems in rubber-technology arising from the sensitivity natural rubber shows towards UV-radiation (e.g. sunlight), heat, and ozone: For this reason more than half of the rubber demand nowadays is satisfied by the chemical industry. However, synthetic rubbers are superior to its natural counterpart not only in regard to their ageing resistance and robustness towards several chemicals: They can easily be adapted to new challenges born by a more and more demanding technology – e.g. using improved concepts in the design of rubber molecule architectures, new catalysts or post-polymerization altering of the elastomers. These challenges demand for a deep and clear understanding of rubber's chemistry and physics.
Chemie in unserer Zeit, 2009
Synthetische Kautschuke losen immer mehr Aufgaben, in denen Elastizitat gefragt, Naturkautschuk a... more Synthetische Kautschuke losen immer mehr Aufgaben, in denen Elastizitat gefragt, Naturkautschuk auf Grund seiner Empfindlichkeit gegenuber UV-Licht, Ozon und Hitze aber uberfordert ist: Uber die Halfte der heute verbrauchten Kautschuke stammen aus den Reaktoren der Chemischen Industrie. Synthesekautschuke sind ihrem naturlichen “Vorbild” nicht nur in Sachen Alterungs- und Chemikalienbestandigkeit uberlegen: Sie konnen auserst effektiv an immer neue Anforderungen angepasst werden – etwa durch Variation ihrer Zusammensetzung und Molekularchitektur, durch Einsatz neuer Katalysatoren und Produktionsverfahren und nachtragliche Modifikation des Polymers. Diese Entwicklungsarbeiten erfordern ein vertieftes Verstandnis der Gummichemie und -Physik. Synthetic rubbers help to solve severe problems in rubber-technology arising from the sensitivity natural rubber shows towards UV-radiation (e.g. sunlight), heat, and ozone: For this reason more than half of the rubber demand nowadays is satisfied by the chemical industry. However, synthetic rubbers are superior to its natural counterpart not only in regard to their ageing resistance and robustness towards several chemicals: They can easily be adapted to new challenges born by a more and more demanding technology – e.g. using improved concepts in the design of rubber molecule architectures, new catalysts or post-polymerization altering of the elastomers. These challenges demand for a deep and clear understanding of rubber's chemistry and physics.
Thermochimica Acta, Aug 1, 2020
Isothermal crystallization of cis-1.4-polybutadiene at low temperatures Claus Wrana (Conceptualiz... more Isothermal crystallization of cis-1.4-polybutadiene at low temperatures Claus Wrana (Conceptualization) (Methodology) (Writing-review and editing) (Investigation) (Formal analysis), Jürgen E.K. Schawe (Conceptualization) (Methodology) (Writing-review and editing)
Polymers
Structural relaxation in polymers occurs at temperatures in the glass transition range and below.... more Structural relaxation in polymers occurs at temperatures in the glass transition range and below. At these temperatures, crystallization is controlled by diffusion and nucleation. A sequential occurrence of structural relaxation, nucleation, and crystallization was observed for several homopolymers during annealing in the range of the glass transition. It is known from the literature that all of these processes are strongly influenced by geometrical confinements. The focus of our work is copolymers, in which the confinements are caused by the random sequence of monomer units in the polymer chain. We characterize the influence of these confinements on structure formation and relaxation in the vicinity of the glass transition. The measurements were performed with a hydrogenated nitrile-butadiene copolymer (HNBR). The kinetics of the structural relaxation and the crystallization was measured using fast differential scanning calorimetry (FDSC). This technique was selected because of the...
Journal of Macromolecular Science, Part B
Rubber Chemistry and Technology, 2015
The influence of the third monomer 5-ethylene-2-norbornene (ENB) and peroxide content on cure beh... more The influence of the third monomer 5-ethylene-2-norbornene (ENB) and peroxide content on cure behavior and network structure of peroxide-cured EPDM were investigated by moving die rheometer, NMR relaxation, and dynamic mechanical thermal spectroscopy. According to the rubber elasticity theory, the torque measurement results showed the network structure of peroxide-cured EPDM contained chemical cross-links via combination reaction (Ccom), chemical cross-links via addition reaction (Cadd), and the contribution of entanglement density and network defects to the total cross-link density (CEN). The total cross-link density (Ctot) increased linearly with the peroxide content. The increase of ENB concentration was beneficial for the improvement of cross-linking efficiency of peroxide, but it made the diene conversion of EPDM decrease. CEN was dependent on the third monomer content, which also provided the dominant contribution to the Ctot at low peroxide contents. Furthermore, Ccom and Cad...
Rubber Chemistry and Technology, 2014
The filler network percolation behavior, filler–filler contact, and filler–polymer interaction of... more The filler network percolation behavior, filler–filler contact, and filler–polymer interaction of carbon black (CB)–filled hydrogenated acrylonitrile–butadiene rubber were investigated with the combination of dielectric and mechanical properties, by means of changing CB concentration, CB-specific surface area, cycling deformation for vulcanizates, and rotation speed of rotors in the internal mixer during the mixing process. A dielectric relaxation spectrometer was used to determine the percolation threshold of the CB network, which was made up of filler–filler contact, combined with the percolation theory. Dynamic mechanical analysis and a universal testing machine were employed to observe the filler–filler contact and filler–polymer interaction. The filler–filler bonds were determined by analysis of the Arrhenius plot on the basis of temperature sweep. The filler–polymer interaction and filler–filler contact were determined by hysteresis loss dependence and analysis of the reinforc...
Chemie in Unserer Zeit, Dec 1, 2009
Synthetische Kautschuke losen immer mehr Aufgaben, in denen Elastizitat gefragt, Naturkautschuk a... more Synthetische Kautschuke losen immer mehr Aufgaben, in denen Elastizitat gefragt, Naturkautschuk auf Grund seiner Empfindlichkeit gegenuber UV-Licht, Ozon und Hitze aber uberfordert ist: Uber die Halfte der heute verbrauchten Kautschuke stammen aus den Reaktoren der Chemischen Industrie. Synthesekautschuke sind ihrem naturlichen “Vorbild” nicht nur in Sachen Alterungs- und Chemikalienbestandigkeit uberlegen: Sie konnen auserst effektiv an immer neue Anforderungen angepasst werden – etwa durch Variation ihrer Zusammensetzung und Molekularchitektur, durch Einsatz neuer Katalysatoren und Produktionsverfahren und nachtragliche Modifikation des Polymers. Diese Entwicklungsarbeiten erfordern ein vertieftes Verstandnis der Gummichemie und -Physik. Synthetic rubbers help to solve severe problems in rubber-technology arising from the sensitivity natural rubber shows towards UV-radiation (e.g. sunlight), heat, and ozone: For this reason more than half of the rubber demand nowadays is satisfied by the chemical industry. However, synthetic rubbers are superior to its natural counterpart not only in regard to their ageing resistance and robustness towards several chemicals: They can easily be adapted to new challenges born by a more and more demanding technology – e.g. using improved concepts in the design of rubber molecule architectures, new catalysts or post-polymerization altering of the elastomers. These challenges demand for a deep and clear understanding of rubber's chemistry and physics.
Chemie in unserer Zeit, 2009
Synthetische Kautschuke losen immer mehr Aufgaben, in denen Elastizitat gefragt, Naturkautschuk a... more Synthetische Kautschuke losen immer mehr Aufgaben, in denen Elastizitat gefragt, Naturkautschuk auf Grund seiner Empfindlichkeit gegenuber UV-Licht, Ozon und Hitze aber uberfordert ist: Uber die Halfte der heute verbrauchten Kautschuke stammen aus den Reaktoren der Chemischen Industrie. Synthesekautschuke sind ihrem naturlichen “Vorbild” nicht nur in Sachen Alterungs- und Chemikalienbestandigkeit uberlegen: Sie konnen auserst effektiv an immer neue Anforderungen angepasst werden – etwa durch Variation ihrer Zusammensetzung und Molekularchitektur, durch Einsatz neuer Katalysatoren und Produktionsverfahren und nachtragliche Modifikation des Polymers. Diese Entwicklungsarbeiten erfordern ein vertieftes Verstandnis der Gummichemie und -Physik. Synthetic rubbers help to solve severe problems in rubber-technology arising from the sensitivity natural rubber shows towards UV-radiation (e.g. sunlight), heat, and ozone: For this reason more than half of the rubber demand nowadays is satisfied by the chemical industry. However, synthetic rubbers are superior to its natural counterpart not only in regard to their ageing resistance and robustness towards several chemicals: They can easily be adapted to new challenges born by a more and more demanding technology – e.g. using improved concepts in the design of rubber molecule architectures, new catalysts or post-polymerization altering of the elastomers. These challenges demand for a deep and clear understanding of rubber's chemistry and physics.
Thermochimica Acta, Aug 1, 2020
Isothermal crystallization of cis-1.4-polybutadiene at low temperatures Claus Wrana (Conceptualiz... more Isothermal crystallization of cis-1.4-polybutadiene at low temperatures Claus Wrana (Conceptualization) (Methodology) (Writing-review and editing) (Investigation) (Formal analysis), Jürgen E.K. Schawe (Conceptualization) (Methodology) (Writing-review and editing)
Polymers
Structural relaxation in polymers occurs at temperatures in the glass transition range and below.... more Structural relaxation in polymers occurs at temperatures in the glass transition range and below. At these temperatures, crystallization is controlled by diffusion and nucleation. A sequential occurrence of structural relaxation, nucleation, and crystallization was observed for several homopolymers during annealing in the range of the glass transition. It is known from the literature that all of these processes are strongly influenced by geometrical confinements. The focus of our work is copolymers, in which the confinements are caused by the random sequence of monomer units in the polymer chain. We characterize the influence of these confinements on structure formation and relaxation in the vicinity of the glass transition. The measurements were performed with a hydrogenated nitrile-butadiene copolymer (HNBR). The kinetics of the structural relaxation and the crystallization was measured using fast differential scanning calorimetry (FDSC). This technique was selected because of the...
Journal of Macromolecular Science, Part B
Rubber Chemistry and Technology, 2015
The influence of the third monomer 5-ethylene-2-norbornene (ENB) and peroxide content on cure beh... more The influence of the third monomer 5-ethylene-2-norbornene (ENB) and peroxide content on cure behavior and network structure of peroxide-cured EPDM were investigated by moving die rheometer, NMR relaxation, and dynamic mechanical thermal spectroscopy. According to the rubber elasticity theory, the torque measurement results showed the network structure of peroxide-cured EPDM contained chemical cross-links via combination reaction (Ccom), chemical cross-links via addition reaction (Cadd), and the contribution of entanglement density and network defects to the total cross-link density (CEN). The total cross-link density (Ctot) increased linearly with the peroxide content. The increase of ENB concentration was beneficial for the improvement of cross-linking efficiency of peroxide, but it made the diene conversion of EPDM decrease. CEN was dependent on the third monomer content, which also provided the dominant contribution to the Ctot at low peroxide contents. Furthermore, Ccom and Cad...
Rubber Chemistry and Technology, 2014
The filler network percolation behavior, filler–filler contact, and filler–polymer interaction of... more The filler network percolation behavior, filler–filler contact, and filler–polymer interaction of carbon black (CB)–filled hydrogenated acrylonitrile–butadiene rubber were investigated with the combination of dielectric and mechanical properties, by means of changing CB concentration, CB-specific surface area, cycling deformation for vulcanizates, and rotation speed of rotors in the internal mixer during the mixing process. A dielectric relaxation spectrometer was used to determine the percolation threshold of the CB network, which was made up of filler–filler contact, combined with the percolation theory. Dynamic mechanical analysis and a universal testing machine were employed to observe the filler–filler contact and filler–polymer interaction. The filler–filler bonds were determined by analysis of the Arrhenius plot on the basis of temperature sweep. The filler–polymer interaction and filler–filler contact were determined by hysteresis loss dependence and analysis of the reinforc...