Effect of HTPB structure on prepolymer characteristics and on mechanical properties of polybutadiene-based polyurethanes

Oligobutadiene-based prepolymers and polyurethanes (PU) were prepared from hydroxyl terminated polybutadiene (HTPB), three diisocyanates (aromatic, alicyclic and aliphatic) and two chain extenders (containing hydroxyl or amino groups). The free NCO content in the prepolymers varied systematically and the characteristic of these products were interpreted in terms of NCO group reactivity, propagation reactions and HTPB functionality. The mechanical properties of the polyurethane elastomers derived from the prepolymers were discussed in terms of hard and soft segment structures.     

Life-cycle assessment of hydrogen technologies with the focus on EU critical raw materials and end-of-life strategies

We present the results of a life-cycle assessment (LCA) for the manufacturing and end-of-life (EoL) phases of the following fuel-cell and hydrogen (FCH) technologies: alkaline water electrolyser (AWE), polymer-electrolyte-membrane water electrolyser (PEMWE), high-temperature (HT) and low-temperature (LT) polymer-electrolyte-membrane fuel cells (PEMFCs), together with the balance-of-plant components. New life-cycle inventories (LCIs), i.e., material inputs for the AWE, PEMWE and HT PEMFC are developed, whereas the existing LCI for the LT PEMFC is adopted from a previous EU-funded project. The LCA models for all four FCH technologies are created by modelling the manufacturing phase, followed by defining the EoL strategies and processes used and finally by assessing the effects of the EoL approach using environmental indicators. The effects are analysed with a stepwise approach, where the CML2001 assessment method is used to evaluate the environmental impacts. The results show that the environmental impacts of the manufacturing phase can be substantially reduced by using the proposed EoL strategies (i.e., recycled materials being used in the manufacturing phase and replacing some of the virgin materials). To point out the importance of critical materials (in this case, the platinum-group metals or PGMs) and their recycling strategies, further analyses were made. By comparing the EoL phase with and without the recycling of PGMs, an increase in the environmental impacts is observed, which is much greater in the case of both fuel-cell systems, because they contain a larger quantity of PGMs.     

Synthesis of a PPV‐fluorene derivative: Applications in luminescent devices

Synthesis of a polyfluorene/poly(p‐phenylene vinylene) derivative, the Poly [(9,9′‐di‐hexylfluorenediylvinylene‐alt‐1,4‐phenylenevinylene)‐co‐((9,9′‐(3‐t‐butylpropanoate) fluorene‐1,4‐phenylene)] (LaPPS 42) was performed following Wittig and Suzuki routes. Polyfluorenes and derivatives have been used in electroluminescent devices, and the synthesis described here has the advantage in pave the way to get distinct structures having different emission spectra. An extensive study of its electrochemical, thermomechanical, optical, and structural properties was carried out, as well as its application in electroluminescent devices. Polymer light‐emitting diodes (PLEDs) and polymer light‐emitting electrochemical cells (PLECs) were built using LaPPS 42 as active layer, and their electric and optical characterizations confirm they have a potential as active element in electroluminescent devices. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42579.     

A contribution to the interpretation of polymer viscoelasticity in DMTA testing

Some ideas relevant to the prevailing viscoelasticity interpretations of dynamic mechanical thermal analysis (DMTA) experiments are presented. The main aspect is the inclusion of kinetic energy and inertia as variables, seeing the relaxing mass constantly increasing during strain, assigning inertial variation and not viscosity to energy dissipation. The equations developed make it possible to obtain the values of important viscoelastic properties, under in any experimental condition, with the data taken from previous experiments.     

Persönlichkeit 2.0

Online Social Networks (OSNs) wie MySpace, Facebook und StudiVZ sind inzwischen zu einem wichtigen Bestandteil des allt?glichen Miteinanders geworden. Entgegen der weit verbreiteten Meinung vermitteln Profile in OSNs kein verf?lschtes, selbstidealisiertes, sondern ein sehr genaues Bild von der Pers?nlichkeit der Profilbesitzer. Dies k?nnte ein wichtiger Grund für die Beliebtheit sozialer Netzwerke sein: Sie bieten eine Plattform für reale soziale Interaktionen und erm?glichen den Ausdruck der eigenen Pers?nlichkeit. Implikationen für den Datenschutz in OSNs werden diskutiert.     

Automatic Generation of Language-based Tools

Many tools can be automatically derived from formal language definitions, such as compilers/interpreters, editors, analyzers, visualizers/animators, etc. Some examples of language-based tools generated automatically by the LISA system are described in the paper. In addition the specification of an algorithm animator and program visualizer, Alma, generated from an extended LISA input-grammar is discussed; LISA principles and code are reused in Alma implementation.     

Reconfigurable digital controller for a buck converter based on FPGA

This paper presents a complete digitally controlled dc–dc buck converter performed by FPGA circuitry. All tasks, analog to digital conversion, control algorithm and pulse width modulation, were implemented in the FPGA. This approach enables high-speed dynamic response and programmability by the controller, without external passive components. In addition, the controller’s structure can be easily changed without external components. The applied algorithm enables a switching frequency of 100 kHz.     

Temperature profile modelling in fuel-coolant interaction codes

To improve the determination of heat and mass transfer in fuel-coolant interaction codes appropriate knowledge of the conditions inside the melt droplets is needed. A simplified mathematical model for the determination of the melt droplet conditions is introduced, considering the material physical properties of the melt droplet. Since the computational demand of the mathematical model would significantly increase the overall computational time of the fuel-coolant interaction codes, a simplification based on the temperature profile approach is presented. Finally, a physically-based approach, which is simple enough to be practical for the implementation into computer codes and complex enough to consider adequately the material properties, is proposed and validated.     

Effect of light, solvents and commercial enzymes on the solubility and stability of sesquiterpene lactones from chicory roots

Summary The solubility of lactucin, 8-deoxylactucin and lactucopicrin, all sesquiterpene lactones of chicory roots, was determined as a function of pH (pH 1–10) in the presence and absence of polysaccharides. The stability of the sesquiterpene lactones, when dissolved in water, decreased under influence of daylight as a function of pH. Enzymatic hydrolysis of lactucopicrin by commercial enzyme preparations, used for liquefaction of chicory roots into lactucin and p-hydroxyphenylacetic acid, was not found.

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Einfluß von Licht, Lösungsmittel und Handelsenzymen auf die Löslichkeit und Stabilität der Sesquiterpen-Lactone von Zichorienwurzeln

Zusammenfassung Die Stabilität von LaCA Bussurnctucin, 8-Deoxylactucin und Lactucopicrin (alles SesquiterpenLactone der Zichorienwurzel) wurde in Abhängigkeit vom pH-Wert beim Aufbewahren im Licht studiert. Es konnte ein Abbau dieser Verbindungen nachgewiesen werden. Die Löslichkeit dieser drei Verbindungen wurde in Abhängigkeit vom pH-Wert mit und ohne Polysaccharide bestimmt. Es wurde keine Hydrolyse des Lactucopicrins unter der Einwirkung von kommerziellen Enzymen, die bei der Verflüssigung von Zichorienwurzeln verwendet werden, gefunden.