High-pressure calorimetry: Thermophysical properties of gases and polymers

During the last decades polymers were important materials for technological progress of our western consumption society. The importance of advanced polymer materials is still increasing and polymers are not only used for packages anymore, but for high-value products such as high-voltage cable insulations, solar cell coatings or medical applications. Due to that, the necessity for optimized and energy efficient processes including a proper waste treatment is increasing. In 2015 worldwide plastic productions were at 322 million tons, mostly common polymers are Polypropylene (PP) and polyethylene (PE) with a content of 48.5%. [1] Some of the production processes, for example low-density polyethylene (LDPE), are performed at high pressures and temperatures of up to 3000 bar and 300 °C. To optimize respective processes, simulation-models have been used more commonly during the last years. Computational models are a comparatively cheap and safe alternative in comparison to actual changes in the process and can be used to test new concepts or recipes. Beside kinetics, simulation-models are based on thermophysical properties such as density or heat capacity. Correlations of these parameters are applied to describe the heat balance of the process and therefore influence the conversion during a simulation-run. To describe a process as detailed as possible, correlations of applied components like monomers or polymers have to rely on exact substance data. Although the temperature dependence of different properties is described well by currently applied correlations, a pressure dependence is mainly achieved by extrapolating fragmentary datasets. These data-sets were partly determined at atmospheric pressure and have not been evaluated further since their publication during the second half of the last century, which makes an application at the demanding polymerization process conditions rather imprecise.Consequently, for an improvement of such simulation-models new and exact substance data at the respective process conditions are required. In this work high-pressure calorimetry has been used for this purpose. Regular calorimetric devices, such as the DSC, have been applied to determine thermophysical properties at atmospheric pressure, but they are not suited for measurements at higher pressures. Such conditions require precise sensor technologies combined with rather massive mountings to withstand the extreme conditions. One device, which merges these properties is the transitiometer. This special Tian-Calvet calorimeter can withstand pressures up to 4000 bar without a decrease in precision. In a measurement one parameter (temperature, pressure or volume) is kept constant, the second one is varied with time and the third is measured as a function of the first two. Applying a pressure program in the transitiometer, expansion coefficients of different gases and polymers could be calculated when evaluating the measured difference heat fluxes. Coming from a temperature and pressure dependence of expansion coefficients, heat capacities could be determined in both dependencies as well. While testing different experimental setups, a pressure- and temperature dependence of densities of polymers could be calculated as well. In heat capacities of carbon dioxide, ethane or ethene a maximum in the temperature dependence in all measured pressures could be observed, which cannot be seen in methane or nitrogen. Beside a temperature-dependent maximum, a pressure dependent maximum is indicated in those molecules as well. Those maxima might be first experimental evidence of results regarding different molecular-dynamic simulations. Here, phenomena in the super-critical area of a phase diagram so called “Widom-Line” and/or “Frenkel-Line” that indicate a “pseudo” phase transition are predicted. That phenomena divide assumed homogeneous phase of the supercritical area, in a gas-like and a liquid-like region. [2] Next steps will be to validate measured data sets and to compare different types of polymers, including homo- and co-polymers. Additionally, it will be necessary to investigate not only pure substances such as polymers or gases, but to examine excess- and solubility effects between different molecules. First indications of such effects have already been observed since melting points of polymers change with pressure and different pressure media. Such effects might also influence already determined heat capacities or expansion coefficients. Another important task in the future will be the investigation of peroxide kinetics in dependence of pressure, temperature and solvent viscosity. [1] PlasticsEurope, 2016, http://www.plasticseurope.org/documents/document/20161014113313-plastics_the_facts_2016_final_version.pdf [2] T. Bryk and T. Scopigno, J. Phys. Chem. Lett., 2017, 8 (20), pp 4995–5001

Linking process conditions with polymer properties for the LDPE process

Low Density Polyethylene (LDPE) is a polymeric material of great importance on the global marked. Its applications range from commodity purposes such as films, tubes and packaging to the specialty sector including medical products such as implants. One of the characteristics of LDPE is its unique polymeric microstructure exhibiting short- as well as long-chain branching (SCB and LCB) and a broad molecular weight distribution due to the free radical polymerization conditions. The polymeric microstructure of the polymer is mainly dependent on the polymerization process conditions and determines the final product properties and thus also the application area. However, experimental investigations of the free radical polymerization of ethylene are very costly due to the high-pressure (up to 3000 bar) and high-temperature (up to 300°C) conditions. Thus, there is a need for a simulation-based tool to link the process conditions with the resulting LDPE properties. This work presents the successful implementation of a three-step multi-scale modelling approach to reach this aim. A visualization of this approach as well as the benefits of the individual steps is depicted in figure 1. The first step consist of modeling the complex kinetic network of the free radical polymerization of ethylene. Kinetic coefficients can be taken from literature [1] and the numerical solving of the resulting system of differential equations is conducted by the software Predici [2]. This yields average product properties, such as branching densities per 1000 carbon atoms (SCB/1000C and LCB/1000) as well as the molecular weight distribution. Those can be validated against 13C-NMR measurements as well as high-temperature size-exclusion chromatography. Please click Additional Files below to see the full abstract

Influence of reaction conditions on the solution polymerization of vinyl acetate

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Changing the means of managerial work: effects of automated decision support systems on personnel selection tasks

To enhance the quality and efficiency of information processing and decision-making, automation based on artificial intelligence and machine learning has increasingly been used to support managerial tasks and duties. In contrast to classical applications of automation (e.g., within production or aviation), little is known about how the implementation of automation for management changes managerial work. In a work design frame, this study investigates how different versions of automated decision support systems for personnel selection as a specific management task affect decision task performance, time to reach a decision, reactions to the task (e.g., enjoyment), and self-efficacy in personnel selection. In a laboratory experiment, participants (N = 122) were randomly assigned to three groups and performed five rounds of a personnel selection task. The first group received a ranking of the applicants by an automated support system before participants processed applicant information (support-beforeprocessing group), the second group received a ranking after they processed applicant information (support-after-processing group), and the third group received no ranking (no-support group). Results showed that satisfaction with the decision was higher for the support-after-processing group. Furthermore, participants in this group showed a steeper increase in self-efficacy in personnel selection compared to the other groups. This study combines human factors, management, and industrial/ organizational psychology literature and goes beyond discussions concerning effectiveness and efficiency in the emerging area of automation in management in an attempt to stimulate research on potential effects of automation on managers’ job satisfaction and well-being at work

Endurance of quantum coherence due to particle indistinguishability in noisy quantum networks

Quantum coherence, the physical property underlying fundamental phenomena such as multi-particle interference and entanglement, has emerged as a valuable resource upon which modern technologies are founded. In general, the most prominent adversary of quantum coherence is noise arising from the interaction of the associated dynamical system with its environment. Under certain conditions, however, the existence of noise may drive quantum and classical systems to endure intriguing nontrivial effects. In this vein, here we demonstrate, both theoretically and experimentally, that when two indistinguishable non-interacting particles co-propagate through quantum networks affected by non-dissipative noise, the system always evolves into a steady state in which coherences accounting for particle indistinguishabilty perpetually prevail. Furthermore, we show that the same steady state with surviving quantum coherences is reached even when the initial state exhibits classical correlations.Comment: arXiv admin note: substantial text overlap with arXiv:1709.0433

Click chemistry within LDPE

Specialty LDPE copolymers provide some of the highest added value polyolefin applications and, in the quest to differentiate in an increasingly commoditized polyolefin environment, are of considerable interest to LDPE producers and other polyolefin players.1 In 2015, global specialty LDPE copolymers production was estimated around 6900 kT, from those EVA (Ethylene Vinyl Acetate) accounts for nearly 90 % of it.1 Other examples are EBA (Ethylene Butyl Acrylate), EVOH (Ethylene Vinyl Alcohol), COC (Cyclic Olefin Copolymer), MAH (Maleic AnHydride) grafted PE, … which all have their specific properties and are used in different kind of applications. All above mentioned commercial grades are made either by in reactor functionalization, copolymerization of ethylene and a monomer, or by post-modification, grafting of a monomer onto a PE backbone. A combination of both routes would give the advantage of producing one base grade; therefore, no changes in reactor settings are required and the properties of the polymer can be tuned by post-modification reactions. Please download the file below for full content

Role of ATP-sensitive potassium channels on hypoxic pulmonary vasoconstriction in endotoxemia

Background: ATP-regulated potassium channels (KATP) regulate pulmonary vascular tone and are involved in hypoxic pulmonary vasoconstriction (HPV). In patients with inflammation like sepsis or ARDS, HPV is impaired, resulting in a ventilation-perfusion mismatch and hypoxia. Since increase of vascular KATP channel Kir6.1 has been reported in animal models of endotoxemia, we studied the expression and physiological effects of Kir6.1 in murine endotoxemic lungs. We hypothesized that inhibition of overexpressed Kir6.1 increases HPV in endotoxemia. Methods: Mice (C57BL/6; n = 55) with (n = 27) and without (n = 28) endotoxemia (35 mg/kg LPS i.p. for 18 h) were analyzed for Kir6.1 gene as well as protein expression and HPV was examined in isolated perfused mouse lungs with and without selective inhibition of Kir6.1 with PNU-37883A. Pulmonary artery pressure (PAP) and pressure-flow curves during normoxic (FiO2 0.21) and hypoxic (FiO2 0.01) ventilation were obtained. HPV was quantified as the increase in perfusion pressure in response to hypoxic ventilation in mmHg of baseline perfusion pressure (ΔPAP) in the presence and absence of PNU-37883A. Results: Endotoxemia increases pulmonary Kir6.1 gene (+ 2.8 ± 0.3-fold) and protein expression (+ 2.1 ± 0.3-fold). Hypoxia increases HPV in lungs of control animals, while endotoxemia decreases HPV (∆PAP control: 9.2 ± 0.9 mmHg vs. LPS: 3.0 ± 0.7 mmHg, p < 0.05, means ± SEM). Inhibition of Kir6.1 with 1 μM PNU-37883A increases HPV in endotoxemia, while not increasing HPV in controls (∆PAP PNU control: 9.3 ± 0.7 mmHg vs. PNU LPS: 8.3 ± 0.9 mmHg, p < 0.05, means ± SEM). Conclusion: Endotoxemia increases pulmonary Kir6.1 gene and protein expression. Inhibition of Kir6.1 augments HPV in murine endotoxemic lungs

Mechanical and mechanical-chemical weed control in sugar beets (Beta vulgaris subsp. vulgaris) - trials in Lower Saxony

Im Ökolandbau wird seit einigen Jahren die Zuckerrübe wieder im Vertragsanbau von Nord- und Südzucker angeboten. Bei Nordzucker nimmt die Anbaufläche von Biozuckerrüben stetig zu. Im Ökolandbau müssen ausschließlich mechanische oder thermische Unkrautregulierungsverfahren eingesetzt werden. Das Kernziel ist, den kostenintensiven Aufwand für die Handhacke zu reduzieren. Flankierend ist die Unkrautregulierung mit reihenunabhängig arbeitenden Zinkenstriegeln oder der Sternrollhacke möglich. Das ist vor allem für Ökobetriebe eine zentrale Frage, da diese Technik in der Regel vorhanden ist. Eine Möglichkeit der Reduktion von Herbiziden im konventionellen Zuckerrübenanbau bietet die mechanische und mechanisch-chemische Unkrautregulierung mit Scharhacken in Verbindung mit einer Bandspritzeinrichtung. Moderne kameragesteuerte Scharhacken mit Bandspritzeinrichtung können eine leistungsfähige Unkrautkontrolle ermöglichen, wenn sie effektiv ins konventionelle System eingebunden werden. Im praktischen Einsatz erweist sich dies jedoch als besondere Herausforderung, da die Kamerasysteme noch ihre Schwächen haben. So können kameragesteuerte Maschinen erst zum Einsatz kommen, wenn die Kulturpflanzenreihen von den Kamerasystemen genau erkannt werden. Dieses wird seit 2016 bei der Landwirtschaftskammer Niedersachsen untersucht.In organic farming, sugar beet has been offered again for contract cultivation from Nord- und Südzucker for several years. At Nordzucker, the area of organically produced sugar beets is steadily increasing. In organic farming, only mechanical or thermal weed control methods are allowed to be used. The core objective is to significantly reduce the costs for the hand hoe. Weed control with independent working comb harrow or rotary hoe is also possible. This is a central question for organic farms, as this technology is usually available. One option for the reduction of herbicides in conventional sugar beet cultivation is provided by mechanical and mechanical-chemical weed control with camera-controlled hoes in conjunction with a band spraying equipment. Modern camera-driven hoeing machines with band spraying equipment can enable efficient weed control if they are effectively integrated into the conventional system. This is being examined at the Chamber of Agriculture of Lower Saxony since 2016. However, the camera-controlled hoeing machines can only be used when the crop rows are accurately recognized by the camera systems. In practical use, however, this proves to be a special challenge, since the camera systems still have their weaknesses

Scenario-based mission statements; Promoting sustainable urban development in the context of the energy transition

Using a planning process for the Stuttgart Neckar Valley as a case study, this paper analyzes the urban inertial forces that counteract the transformation of energy infrastructure areas in the context of the energy transition. In order to overcome these forces, a scenario-based mission statement was developed in which spatial scenarios were derived from energy scenarios and finally summarized in a concept plan for the Neckar Valley. The mission statement was developed following an analytical-deliberative and transdisciplinary approach. The approach to mission statement development presented here can respond flexibly to changing framework conditions and thus serve as a model for other cities with large-scale energy infrastructures in transition.Am Beispiel eines Planungsprozesses für das Stuttgarter Neckartal wird analysiert, welche urbanen Beharrungskräfte einer städtebaulichen Transformation von Energieinfrastrukturflächen im Rahmen der Energiewende entgegenwirken. Um diese Kräfte zu überwinden wurde ein szenariobasiertes Leitbild entwickelt, in dem auf Basis energiewirtschaftlicher Szenarien räumliche Szenarien abgeleitet und schließlich in einem Konzeptplan für das Neckartal zusammengeführt wurden. Zur Entwicklung des Leitbilds wurde ein analytisch-deliberatives und transdisziplinäres Vorgehen verfolgt. Der vorgestellte Ansatz der Leitbildentwicklung kann flexibel auf sich verändernde Rahmenbedingungen reagieren und daher als Vorbild für andere Städte mit großmaßstäblichen Energieinfrastrukturen dienen, die sich im Rahmen der Energiewende verändern werden