scholarly journals Space Charges as Pre-breakdown Phenomena in Solid Dielectrics: A Concise Approach and Some Critical Comments

2020 ◽  
Vol 10 (4) ◽  
pp. 5992-5997
Author(s):  
M. Danikas ◽  
G. E. Vardakis ◽  
R. Sarathi
Keyword(s):  
Polymeric Materials ◽  
Short Review ◽  
Space Charges ◽  
Solid Dielectrics ◽  
The Relationship

This short review deals with some aspects of space charges in solid dielectrics, and in particular in polymeric materials. The relationship between space charges and pre-breakdown events is discussed and the importance of space charges for the breakdown of solid dielectrics is emphasized.

scholarly journals Ignition and advancement of surface discharges at atmospheric air under positive lightning impulse voltage depending on perpendicular electric stress and solid dielectrics: modelling of the propagating phenomenology

2018 ◽  
Vol 82 (2) ◽  
pp. 20801 ◽  
Author(s):  
Mohammed Adnane Douar ◽  
Abderrahmane Beroual ◽  
Xavier Souche
Keyword(s):  
Electric Field ◽  
Electrostatic Field ◽  
Physical Mechanisms ◽  
Space Charges ◽  
Electric Stress ◽  
Impulse Voltage ◽  
Lightning Impulse ◽  
Surface Discharges ◽  
Solid Dielectrics ◽  
The Relationship

In many high voltage equipment, partial discharges are regarded as one of the most widespread pathology whose ignition conditions and effects are studied by scientists and manufacturers to avoid major failures. Actually, those electrical gaseous phenomena generally occur under several constraints such as the electrostatic field level, the nature of insulating surface being polluted or not, and switching or lightning transients. The present paper discusses physical mechanisms related to the creeping discharges propagation growing over insulators subjected to perpendicular electric field and positive lightning impulse voltage. More precisely, the developed discussion attempts to answer some observations especially noticed for main discharges feature namely (i) the discharges morphology, (ii) their velocity and (iii) the space charges effects on electric field computation. Several factors like (i) the influence of the type of a material’s interface, its electric conductivity, permittivity and discharges mobility, (ii) the relationship between the applied electrostatic field, the space charges, the velocity, the propelling pressure and discharges temperature are among numerous parameters that have been addressed in this study which discusses lightning impulse transients phenomena.

scholarly journals Foreign Inclusions, Enclosed Cavities, Partial Discharge Models and Discharge Energy: A Short Review Regarding Solid Dielectrics and Composite Insulating Systems

2019 ◽  
Vol 9 (5) ◽  
pp. 4659-4666 ◽  
Author(s):  
M. Danikas ◽  
S. Morsalin
Keyword(s):  
Partial Discharge ◽  
Short Review ◽  
Partial Discharges ◽  
Discharge Energy ◽  
Insulating Materials ◽  
Discharge Parameters ◽  
Solid Dielectrics ◽  
The Relationship ◽  
Inception Voltage

Partial discharges in cavities are one of the main reasons of breakdown of insulating materials and insulating systems in general. The present paper aims at commenting some aspects of the relation between partial discharges and insulation damage. Some basic models explaining the workings and impacts of discharges in cavities are discussed. Discussions about the possibility of damage in the presence of multiple cavities as well as of the risks of minute discharges and/or charging phenomena below the so-called inception voltage are conducted. It is remarked that the question of the relationship between discharge parameters and insulation damage is still an important one, especially for composite insulating systems.

Carbon Dioxide as a Carbon Resource – Recent Trends and Perspectives

2012 ◽  
Vol 67 (10) ◽  
pp. 961-975 ◽  
Author(s):  
Markus Hölscher ◽  
Christoph Gürtler ◽  
Wilhelm Keim ◽  
Thomas E. Müller ◽  
Martina Peters ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Raw Materials ◽  
Low Cost ◽  
Polymeric Materials ◽  
Short Review ◽  
Chemical Research ◽  
Bond Forming ◽  
Bulk Chemicals ◽  
High Thermodynamic Stability ◽  
Recent Trends

With the growing perception of industrialized societies that fossil raw materials are limited resources, academic chemical research and chemical industry have started to introduce novel catalytic technologies which aim at the development of economically competitive processes relying much more strongly on the use of alternative carbon feedstocks. Great interest is given world-wide to carbon dioxide (CO2) as it is part of the global carbon cycle, nontoxic, easily available in sufficient quantities anywhere in the industrialized world, and can be managed technically with ease, and at low cost. In principle carbon dioxide can be used to generate a large variety of synthetic products ranging from bulk chemicals like methanol and formic acid, through polymeric materials, to fine chemicals like aromatic acids useful in the pharmaceutical industry. Owing to the high thermodynamic stability of CO2, the energy constraints of chemical reactions have to be carefully analyzed to select promising processes. Furthermore, the high kinetic barriers for incorporation of CO2 into C-H or C-C bond forming reactions require that any novel transformation of CO2 must inevitably be associated with a novel catalytic technology. This short review comprises a selection of the most recent academic and industrial research developments mainly with regard to innovations in CO2 chemistry in the field of homogeneous catalysis and processes.

scholarly journals Internal donors on supported Ziegler Natta catalysts for isotactic polypropylene: a brief tutorial review

2021 ◽  
Vol 28 (10) ◽  
Author(s):  
Bharat R. Paghadar ◽  
J. B. Sainani ◽  
Samith K. M. ◽  
Poornima Bhagavath
Keyword(s):  
Polymeric Materials ◽  
Detailed Comparison ◽  
Short Review ◽  
Point Of View ◽  
Polymer Science ◽  
Cross Combination ◽  
Polymer Properties ◽  
Technical Advances ◽  
Catalyst Systems ◽  
New Applications

AbstractThe scientific and technical advances in the field of polymer science has been abundant in recent years. Amongst the various polymeric materials available in market, synthesis of polyolefins has been in the forefront since decades. A major challenge in this domain remains in attaining stereoregular polyolefins especially polypropylene (PP) and significant efforts were carried out by synthesizing various internal donors (ID) aiding the catalysts involved in producing them. This short review gives an overview of i) various generations of Ziegler–Natta (ZN) catalyst systems ii) general classes of ID that has been demonstrated by the researchers over the past decades iii) their influence on PP isotacticity and polymer properties. The coordination modes of different donor classes on supported ZN system and comparative study especially between phthalate and diether ID classes were also addressed here. This review also presents the studies carried out on phthalate catalyst structure analysis, detailed comparison study on phthalate and diether IDs in terms of PP isotacticity, regioselectivity, hydrogen response, and also their cross combination study and competitive behavior. Further a brief description on other structurally varied IDs like malonates, maleates, silyl diol esters, bifunctional donors, multi ether donors demonstrated for isotactic PP were also presented. Studies conducted on compatibility of incorporation of two different classes of IDs on a single supported ZN system for the fundamental understanding of the catalyst behavior; and also on how mixed donor approach enables in tuning the catalyst for polymer properties were also presented. This review also provides an opportunity to the young minds and the basic researchers from academic point of view by and large to create new polymeric materials with useful properties or modify the existing materials for new applications by incorporating new IDs for further improvisation of the stereo regularity in obtaining the polymers. Graphic Abstract

scholarly journals Lifetime Prediction Methods for Degradable Polymeric Materials—A Short Review

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4507 ◽  
Author(s):  
Angelika Plota ◽  
Anna Masek
Keyword(s):  
Polymeric Materials ◽  
Short Review ◽  
Isoconversional Method ◽  
Lifetime Prediction ◽  
Accelerated Ageing ◽  
Radiation Chemical ◽  
Degradation Reactions ◽  
Wlf Model ◽  
Advanced Isoconversional Method ◽  
The Impact

The determination of the secure working life of polymeric materials is essential for their successful application in the packaging, medicine, engineering and consumer goods industries. An understanding of the chemical and physical changes in the structure of different polymers when exposed to long-term external factors (e.g., heat, ozone, oxygen, UV radiation, light radiation, chemical substances, water vapour) has provided a model for examining their ultimate lifetime by not only stabilization of the polymer, but also accelerating the degradation reactions. This paper presents an overview of the latest accounts on the impact of the most common environmental factors on the degradation processes of polymeric materials, and some examples of shelf life of rubber products are given. Additionally, the methods of lifetime prediction of degradable polymers using accelerated ageing tests and methods for extrapolation of data from induced thermal degradation are described: the Arrhenius model, time–temperature superposition (TTSP), the Williams–Landel–Ferry (WLF) model and 5 isoconversional approaches: Friedman’s, Ozawa–Flynn–Wall (OFW), the OFW method corrected by N. Sbirrazzuoli et al., the Kissinger–Akahira–Sunose (KAS) algorithm, and the advanced isoconversional method by S. Vyazovkin. Examples of applications in recent years are given.

Modeling the Elasticity of Oriented Electrospun Nano-Fibrous Scaffold

2011 ◽  
Vol 467-469 ◽  
pp. 1241-1244
Author(s):  
Bo Yuan ◽  
Qun Feng Liu ◽  
Cai Lin ◽  
Xiao Feng Chen
Keyword(s):  
Elastic Modulus ◽  
Micromechanical Model ◽  
Polymeric Materials ◽  
Segment Length ◽  
Fibrous Scaffold ◽  
Fiber Concentration ◽  
Linear Elastic ◽  
Electrospinning Method ◽  
Percolation Effect ◽  
The Relationship

A micromechanical model is constructed for the elastic modulus of nano-fibrous scaffold. The nano-fibrous scaffold was obtained using electrospinning method with polymeric materials, and was supposed to be created with linear elastic strain rods that are straight in the range of rod length. Statistical theory was introduced to model the random distribution of fiber segment length and the percolation effect was also studied. Model predictions were verified using experimental data. This model can be used to study the relationship between the elastic modulus of the scaffold with respect to the fiber concentration, fiber diameter and fiber orientation.

scholarly journals "Click" chemistry as a tool to create novel biomaterials: a short review

2017 ◽  
Vol 1 (1) ◽  
pp. 22-34
Author(s):  
Mariana Barbosa ◽  
Cristina Martins ◽  
Paula Gomes
Keyword(s):  
Click Chemistry ◽  
Biomedical Applications ◽  
Recent Literature ◽  
Click Reaction ◽  
Cycloaddition Reaction ◽  
Polymeric Materials ◽  
Short Review ◽  
Dipolar Cycloaddition ◽  
Functionalization Of Polymers ◽  
Grafting Modification

In recent years, there has been a growing demand for novel strategies for biomedical applications. Chitosan is a typical cationic amino-containing polysaccharide that has been widely used due to its unique properties. The grafting modification of chitosan has been explored as an interesting method to develop multifunctional novel chitosan hybrid materials for drug delivery, tissue engineering, and other biomedical applications. Recently, “click” chemistry has been introduced into the synthesis of polymeric materials with well-defined and complex chain architectures. The Huisgen’s 1,3-dipolar cycloaddition reaction between alkynes and azides yielding triazoles is the principal example of a “click” reaction. Bioconjugation, surface modification, and orthogonal functionalization of polymers were successfully performed through this chemoselective reaction. In recent literature interest has been shown in this cycloaddition for the modification of polysaccharides, however, only a few chitosan graft copolymers have been synthesized by this technique.

scholarly journals Plastics: the world trends of production, application, processing and recycling. Short review of K-2019 and Plast Eurasia 2019 Exhibitions

2020 ◽  
pp. 53-60
Author(s):  
V. V. Abramov ◽  
N. M. Chalaya ◽  
O. I. Abramushkina
Keyword(s):  
Polymeric Materials ◽  
Short Review ◽  
Amount Of Information ◽  
The World

In a brief review, the authors tried to present the main trends in the development of the plastics manufacturing, processing, consumption and recycling sectors. When considering various types of polymeric materials, the authors drew attention to the emergence of a new brand assortment, which, in turn, led to the expansion of the plastics application. From a large amount of information, the most striking examples were selected, confirming trends noted by the authors.

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