1,721,160 research outputs found
CALORIMETRIC STUDY OF THE INHIBITION OF THE RUNAWAY REACTION DURING POLYMERIZATION PROCESSES
No full textEffect of Amine Compounds on the Self-Polymerisation of Methyl Methacrylate
No full textThis work is the result of the experimental analysis of the effect of different alkyl anilines (accelerators) on the self-polymerisation of methyl methacrylate. The state of the art before this study suggested that there should have been no significant increase in the rate of polymerisation reaction until the initiator (typically a peroxide) is added to the stabilised mixture of monomer and accelerator. All the experimental results found during this investigation indicated instead that the accelerators can affect the rate of polymerisation even if no peroxide is present in the system. Different kinds of alkyl anilines in methyl methacrylate have been tested by differential scanning calorimetry and adiabatic calorimetry. The experimental data allowed us to define safety ranges for the polymerisation reaction
Post Investigation of an Incident due to the Self-Polymerisation of a Commercial Monomer
No full textIn the last decade, the importance of risk analysis in the transport of dangerous goods has been evidenced by several studies showing that in some cases the risk associated with the transport of hazardous substances can be compared to those in chemical plants (processing units and storage).
In this work the analysis of an accident in transport of dangerous goods is described. The objective of this study is to contribute to the determination of the causes that brought about the self-polymerization of commercial divinylbenzene (DVB 63%) contained in an isothermal-container, in order to prevent future occurrence of this type of accidents.
Residence time and conditions during transport and storage of monomers, in particular the storage temperature, are very important factors that affect their self-polymerization aptitude. Concerning the cause of accidents it has been supposed that the quantity of oxygen in the tanker probably was insufficient to activate properly the inhibition mechanism to prevent the self-polymerization. According to this consideration the self-polymerization of DVB and the inhibition mechanism of 4-tert-Butylcatechol (TBC) have been studied as a function of temperature and monomer exposure to air with Differential Scanning Calorimetry and Adiabatic Calorimetry
Evaluation of Safety Scenarios for Fires in Waste Disposal Facilities through Numerical Simulations
Full text linkAfter several high-profile fires in waste and recycling facilities, the industry is put under pressure, especially as the materials processed in waste recycling are getting increasingly dangerous. Fire is an ever-present possibility at most waste management sites requiring proper preventive and mitigative strategies because it can cause significant damage to people, property and the environment. Fire risk assessment may benefit from applying the concept of fire safety engineering and numerical tools to approach the phenomena quantitatively. However, the complexity of such fire scenarios requires a detailed analysis that also involves an insight into fundamental processes, including pyrolysis of solid waste matrices and combustion of pyrolizate. These steps are critical for defining safety features of fire scenarios in waste disposal facilities, but the availability of input data may limit the modelling capability of numerical tools. The present work deals with modelling a fire scenario of a bale of plastics starting from literature data in which both pyrolysis and combustion are addressed. Having an accurate reaction model is of paramount importance in modelling solid waste fires. However, full-scale fire tests in open fields will be required to validate and systematize how piles of material burn dependently on boundary conditions
Addressing waste disposal fires in open fields through large eddy simulations
No full textAddressing fires in waste disposal facilities is of topical interest for firefighting and environmental protection. Statistics of fires that involve fuel matrixes made of diversified wastes are escalating and ask for an effective response, both in prevention and mitigation. Crucial to this target is the consideration of underlying phenomena, and modeling of fire dynamics and pollutant emission also via robust numerical simulations. In this work, fires in waste disposal facilities are addressed with Large Eddy Simulation to test the capability to catch the main phenomena of the combustion of wastes made of plastic and the consequent emission of pollutants. This approach is applied to fuel matrixes in form of piles of different sizes, made of polyolefins and polyvinylchloride burned in an open field. The atmospheric dispersion of pollutants, including soot, carbon monoxide, carbon dioxide, and hydrogen chloride are investigated under different environmental conditions. Besides, thermal aspects are addressed to come up with indications of the heat release rate
Evaluation of Time Varying Parameters in Polymerization Reactors by means of Temperature Oscillation Calorimetry
No full textDiuretics in hypertension.
No full textDespite the consistent reduction in the incidence of stroke and coronary events demonstrated in numerous clinical trials in young and elderly hypertensive subjects, the use of diuretics has declined as a first-line therapy in hypertension. The metabolic dose-dependent side effects and the increasing availability of new drugs appear the two main reasons for the decline. Although the neutral metabolic effects and the perception of a more physiological approach to hypertension has been advocated with the newer agents, no definite proof has been reported on the long-term effects on cardiovascular end-points. Many of adverse effects of diuretics can be limited by the use of low doses. For this reason, as well as their efficacy, safety, and cost-effectiveness, diuretics should remain a first-line therapy for hypertensive patients
OPTIMIZATION OF BATCH POLYMERIZATION REACTORS - MODELING AND EXPERIMENTAL RESULTS FOR SUSPENSION POLYMERIZATION OF METHYLMETHACRYLATE
No full textA model for the simulation of suspension polymerization of MMA has been developed, which allows to account for the effect of diffusive phenomena on reaction rate and to evaluate molecular weight distribution under non-isothermal conditions. The model has been validated by experimental runs carried out in a laboratory reactor. Obtained results show that an increase of the reaction temperature during the gel effect time can have a favourable influence on the polymer quality. The control of temperature profiles in the reactor is indicated as an interesting operating strategy to be adopted in industrial units
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