Charge Transport in LDPE Nanocomposites Part I—Experimental Approach

This work presents results of bulk conductivity and surface potential decay measurements on low-density polyethylene and its nanocomposites filled with uncoated MgO and Al2O3, with the aim to highlight the effect of the nanofillers on charge transport processes. Material samples at various filler contents, up to 9 wt %, were prepared in the form of thin films. The performed measurements show a significant impact of the nanofillers on reduction of material’s direct current (dc) conductivity. The investigations thus focused on the nanocomposites having the lowest dc conductivity. Various mechanisms of charge generation and transport in solids, including space charge limited current, Poole-Frenkel effect and Schottky injection, were utilized for examining the experimental results. The mobilities of charge carriers were deduced from the measured surface potential decay characteristics and were found to be at least two times lower for the nanocomposites. The temperature dependencies of the mobilities were compared for different materials

Highly porous flame-retardant and sustainable biofoams based on wheat gluten and in situ polymerized silica

Wheat gluten from ethanol production is presented as flame-retardant silica hybrid biofoams for insulation. The porosity of 90% and self-extinguishing nature make them an attractive alternative to petroleum-based foams.</p

Nanocomposites and polyethylene blends: two potentially synergistic strategies for HVDC insulation materials with ultra-low electrical conductivity

Among the various requirements that high voltage direct current (HVDC) insulation materials need to satisfy, sufficiently low electrical conductivity is one of the most important. The leading commercial HVDC insulation material is currently an exceptionally clean cross-linked low-density polyethylene (XLPE). Previous studies have reported that the DC-conductivity of low-density polyethylene (LDPE) can be markedly reduced either by including a fraction of high-density polyethylene (HDPE) or by adding a small amount of a well dispersed, semiconducting nanofiller such as Al2O3 coated with a silane. This study demonstrates that by combining these two strategies a synergistic effect can be achieved, resulting in an insulation material with an ultra-low electrical conductivity. The addition of both HDPE and C8–Al2O3 nanoparticles to LDPE resulted in ultra-insulating nanocomposites with a conductivity around 500 times lower than of the neat LDPE at an electric field of 32 kV/mm and 60–90 \ub0C. The new nanocomposite is thus a promising material regarding the electrical conductivity and it can be further optimized since the polyethylene blend and the nanoparticles can be improved independently

Validation of a 3D CT method for measurement of linear wear of acetabular cups: A hip simulator study

Background We evaluated the accuracy and repeatability of a 3D method for polyethylene acetabular cup wear measurements using computed tomography (CT). We propose that the method be used for clinical in vivo assessment of wear in acetabular cups. Material and methods Ultra-high molecular weight polyethylene cups with a titanium mesh molded on the outside were subjected to wear using a hip simulator. Before and after wear, they were (1) imaged with a CT scanner using a phantom model device, (2) measured using a coordinate measurement machine (CMM), and (3) weighed. CMM was used as the reference method for measurement of femoral head penetration into the cup and for comparison with CT, and gravimetric measurements were used as a reference for both CT and CMM. Femoral head penetration and wear vector angle were studied. The head diameters were also measured with both CMM and CT. The repeatability of the method proposed was evaluated with two repeated measurements using different positions of the phantom in the CT scanner. Results The accuracy of the 3D CT method for evaluation of linear wear was 0.51 mm and the repeatability was 0.39 mm. Repeatability for wear vector angle was 17?. Interpretation This study of metal-meshed hip-simulated acetabular cups shows that CT has the capacity for reliable measurement of linear wear of acetabular cups at a clinically relevant level of accuracy

Essential classical thermodynamics

This book is a concise, readable, yet authoritative primer of basic classic thermodynamics. Many students have difficulty with thermodynamics, and find at some stage of their careers in academia or industry that they have forgotten what they learned, or never really understood these fundamental physical laws. As the title of the book suggests, the author has distilled the subject down to its essentials, using many simple and clear illustrations, instructive examples, and key equations and simple derivations to elucidate concepts. Based on many years of teaching experience at the undergraduate and graduate levels, “Essential Classical Thermodynamics” is intended to provide a positive learning experience, and to empower the reader to explore the many possibilities for applying thermodynamics in other fields of science, engineering, and even economics where energy plays a central role. Thermodynamics is fun when you understand it

Polymer physics

This book is the result of my teaching efforts during the last ten years at the Royal Institute of Technology. The purpose is to present the subject of polymer physics for undergraduate and graduate students, to focus the fundamental aspects of the subject and to show the link between experiments and theory. The intention is not to present a compilation of the currently available literature on the subject. Very few reference citations have thus been made. Each chapter has essentially the same structure: starling with an introduction, continuing with the actual subject, summarizing the chapter in 30D-500 words, and finally presenting problems and a list of relevant references for the reader. The solutions to the problems presented in Chapters 1-12 are given in Chapter 13. The theme of the book is essentially polymer science, with the exclusion of that part dealing directly with chemical reactions. The fundamentals in polymer science, including some basic polymer chemistry, are presented as an introduction in the first chapter. The next eight chapters deal with different phenomena (processes) and states of polymers. The last three chapters were written with the intention of making the reader think practically about polymer physics. How can a certain type of problem be solved? What kinds of experiment should be conducted? This book would never have been written without the help of my friend and adviser, Dr Anthony Bristow, who has spent many hours reading through the manuscript. criticizing the content

New Insulating Materials for Next Generation of HVDC Cables - Methods for Evaluation of Degradation Phenomena by Electrical Treeing

The ongoing in Sweden research activities aim toelaborate new material concepts that can beapplicable in designing and manufacturing highvoltage direct current (HVDC) cables for very highvoltage levels, up to 800 kV. This task focuses oninvestigating possibilities provided by use ofmaterials containing nanofillers and voltagestabilizers. Variations in breakdown strength,electrical conductivity and control of space chargeswith temperature and composition as well as theirstability during long-term operation are investigated.This paper describes a part of the work thatconcentrates on elaborating a robust methodologyfor testing material resistance to electrical treeinception. It is argued that AC treeing test underramped voltage may effectively be used forscreening candidate materials for applications inHVDC cable insulation

New Insulating Materials for Next Generation of HVDC Cables - Methods for Evaluation of Degradation Phenomena by Electrical Treeing

The ongoing in Sweden research activities aim toelaborate new material concepts that can beapplicable in designing and manufacturing highvoltage direct current (HVDC) cables for very highvoltage levels, up to 800 kV. This task focuses oninvestigating possibilities provided by use ofmaterials containing nanofillers and voltagestabilizers. Variations in breakdown strength,electrical conductivity and control of space chargeswith temperature and composition as well as theirstability during long-term operation are investigated.This paper describes a part of the work thatconcentrates on elaborating a robust methodologyfor testing material resistance to electrical treeinception. It is argued that AC treeing test underramped voltage may effectively be used forscreening candidate materials for applications inHVDC cable insulation

Fundamental polymer science

This successor to the popular textbook, “Polymer Physics” (Springer, 1999), is the result of a quarter-century of teaching experience as well as critical comments from specialists in the various sub-fields, resulting in better explanations and more complete coverage of key topics. With a new chapter on polymer synthesis, the perspective has been broadened significantly to encompass all of polymer science. Polysaccharides and proteins are included in essentially all chapters, while polyelectrolytes are new to the second edition. Cheap computing power has greatly expanded the role of simulation and modeling in the past two decades, which is reflected in many of the chapters. A supplementary chapter on basic thermodynamics is based on a course that the senior author has taught for seven years. Additional problems and carefully prepared graphics aid in understanding. Two principles are key to the textbook’s appeal: 1) Students learn that, independent of the origin of the polymer, synthetic or native, the same general laws apply, and 2) students should benefit from the book without an extensive knowledge of mathematics. Taking the reader from the basics to an advanced level of understanding, the text meets the needs of a wide range of students in chemistry, physics, materials science, biotechnology, and civil engineering, and is suitable for both masters- and doctoral-level students. Praise for the previous edition: ...an excellent book, well written, authoritative, clear and concise, and copiously illustrated with appropriate line drawings, graphs and tables. - Polymer International ...an extremely useful book. It is a pleasure to recommend it to physical chemists and materials scientists, as well as physicists interested in the properties of polymeric materials. - Polymer News This valuable book is ideal for those who wish to get a brief background in polymer science as well as for those who seek a further grounding in the subject. - Colloid Polymer Science The solutions to the exercises are given in the final chapter, making it a well thought-out teaching text. - Polymer Science

Suboptimal light curing and direct exposure to water of two contemporary composites: degree of conversion, sorption, solubility, and Knoop hardness

The water sorption and solubility of two polymer resin‐based dental composite materials were assessed in order to evaluate the effects of immediate post‐cure water exposure on the water sensitivity of the composites. Each material was tested with two different light curing setups. The radiant exposure of the two curing setups differed by a factor of 5. After exposure to water and subsequent drying, the Knoop surface hardness was measured. The change in the degree of conversion in both water and air storage medium within the first 24 h after curing was monitored by Raman spectroscopy. No significant differences in the degree of conversion were detected 24 h after curing. Samples exposed to the lower irradiation dose showed higher solubility and a lower surface hardness than the samples exposed to the higher irradiation dose. Early exposure to water did not cause detectable differences in the ongoing polymerization process. Increase in radiant exposure reduced the fraction of unbound constituents and increased the crosslink density, thereby reducing the plasticity of the material