THE INFLUENCE OF RECIPE FORMULATION AND ELECTRIC FIELD FREQUENCY UPON DIELECTRIC LOSS IN PLASTIFIED PVC FILMS

Plastified polyvinyl chloride (PVC) films are largely used in the clothing and footwear industries. The composition of the PVC-based blend and the curing stage determine the main characteristics of the final films. Lately, radio frequency fields (RF fields) have gained popularity as heat generators in different processing stages of polymer films, like the PVC ones. The dielectric behaviour of PVC films can be controlled by the recipe formulation of plastisol blends. This paper presents the influence of the chemical nature and concentration of some auxiliaries, added in the plastisol blend, upon dielectric loss, tg in plastified PVC films obtained in high frequency electric field. The chemicals used as additives in the recipe formulation were: polydimethylsiloxane (PDMS) polymethylhydrosiloxane (PHDMS), nonylphenol ethoxylate emulsifier NF10 (NE) and collagen hydrolizate (CH). Additives concentration was in the range 4-6 parts. The RF field was provided by a high capacitive generator with 380 V supply voltage, and 13.56 MHz working frequency. Increased concentration of auxiliaries determined the increase of tg irrespective the nature of the chemical auxiliary. The dielectric loss of PVC films, due to the presence of chemical additives, increased in the following order: PDMS< NE< CH< PHDMS. The dielectric loss angle increased in the RF field up to a maximum value that corresponds to a critical frequency. The addition of additives to the plastisol PVC blend, as mono, binary, ternary or quaternary mixture, has a beneficial effect upon the dielectric behaviour of final films, making them suitable for use in the footwear manufacturing

Modeling and Simulation of Rotating Machine Windings Fed by High-Power Frequency Converters for Insulation Design

Modern power systems include a considerable amount of power electronic converters related to the introduction of renewable energy sources, high-voltage direct current (HVDC) systems, adjustable speed drives, and so on. These components introduce repetitive pulses generated by the commutation of semiconductor switches, resulting in overvoltages with very steep fronts and high dielectric stresses. This phenomenon is one of the main causes of accelerated insulation aging of motors in power electronic-based systems. This chapter presents state-of-the-art computational tools for the analysis of motor windings excited by fast-front pulses related to the use of frequency converters based on pulse-width modulation (PWM). These tools can be applied for the accurate prediction of overvoltages and dielectric stresses required to propose insulation design improvements. In the case of the stress-grading system used in medium-voltage (MV) motors, transient finite-element method (FEM) is used to study the effect of fast pulses. It is shown how, by controlling the material properties and the design of the stress-grading systems, solutions to reduce the adverse effects of fast pulses from PWM-type inverters can be proposed

Electrical Insulation Weaknesses in Wide Bandgap Devices

The power electronics research community is balancing on the edge of a game-changing technological innovation: as traditionally silicon (Si) based power semiconductors approach their material limitations, next-generation wide bandgap (WBG) power semiconductors are poised to overtake them. Promising WBG materials are silicon carbide (SiC), gallium nitride (GaN), diamond (C), gallium oxide (Ga2O3) and aluminum nitride (AlN). They can operate at higher voltages, temperatures, and switching frequencies with greater efficiencies compared to existing Si, in power electronics. These characteristics can reduce energy consumption, which is critical for national economic, health, and security interests. However, increased voltage blocking capability and trend toward more compact packaging technology for high-power density WBG devices can enhance the local electric field that may become large enough to raise partial discharges (PDs) within the module. High activity of PDs damages the insulating silicone gel, lead to electrical insulation failure and reduce the reliability of the module. Among WBG devices, electrical insulation weaknesses in WBG-based Insulated Gate Bipolar Transistor (IGBT) have been more investigated. The chapter deals with (a) current standards for evaluation of the insulation systems of power electronics modules, (b) simulation and modeling of the electric field stress inside modules, (c) diagnostic tests on modules, and (d) PD control methods in modules

Fabrication and characterization of composites of a perovskite and polymers with high dielectric permittivity

Composites of strontium titanate (SrTiO3) at loadings up to 50 vol.% with polar poly(butylene terephthalate) (PBT) and non-polar linear low density polyethylene (LLDPE) were prepared to investigate their dielectric responses in the wireless frequency range. The SrTiO3 particles were uniformly dispersed in the polymers at low loadings, but were more bead-like and agglomerated at higher SrTiO3 loadings. The SrTiO3 has a strong nucleating effect on both polymers, increasing the crystallization temperature and reducing the crystallinity of both polymers. Dielectric properties of composites were measured between 2.45−5 GHz. Dielectric permittivity (ε') of composites at 2.45 GHz increased with increasing SrTiO3 content. ε' increased by a factor of 5 for PBT, from 3.7 for unfilled PBT to 16.5 and by a factor of ∼8.5 for unfilled LLDPE, from 2.3 to 19.7 for maximum SrTiO3 loading. The composites had similar dissipation factor values as the unfilled polymers. The Lichtenecker model was in good agreement with the experimental data

Properties and Applications of Polymer Dielectrics

The book gives the reader an overview on electrical properties and applications such as converter transformer, transistor, and energy storage. Besides, this book also presents some recent researches on typical polymer material such as silicon rubber and LDPE, which may provide some clues of advanced polymer properties for both engineers and researches. The author has been a professor at the Department of Electrical Engineering, School of Electrical Engineering and Automation, Tianjin University, China, since 2002. He has been active in polymer insulation research since the 1990s. He is a member of IEEJ, senior member of CSEE, member at several WG in CIGRE, and associate editor of the IEEE Transactions on Dielectrics and Electrical Insulation

Functionalisation of Polymer Thin-Films towards their Application in Biosensing Organic Transistors

Point-of-care devices aim to improve medical treatment, by forecasting diseases before symptoms manifest. Multipurpose, portable and easy-to-use sensing devices would increase the accessibility of diagnostics, supporting the early detection and treatment of diseases. Integration into wearable technology would facilitate constant health monitoring, optimising diagnostic times. Biosensors based on organic transistors and those fabricated with functionalised organic semiconducting polymers, show potential in advancing healthcare towards this envisioned future. The scope of this thesis explores strategies to covalently interface biological receptors to semiconducting polymer thin-films, fabricate and characterise field-effect transistor devices utilising these thin-films, and explore their use as organic transistor biosensors. The first research chapter (Chapter 3) identifies a foundational organic field-effect transistor (OFET) fabrication methodology incorporating a high-performance polymer (DPP-DTT). Assembly of large-area homogeneous thin-films, via a floating thin-film transfer method was emphasised. Influence of oxygen and nitrogen plasma treatment on the characteristics of OFETs were investigated. Nitrogen plasma modified thin-films observed exploitable chemical functionalities for receptor attachment. In Chapter 4 thin-films composed of DPP-DTT blended with a cross-linking agent, glutaraldehyde, were incorporated into OFETs. The methodology facilitated the attachment of receptors onto the thin-film surface. Morphology, modified surface chemistry and preliminary OFET biosensing performance were investigated. Chapter 5 details research on fabricating OFETs using an azide modified DPP-DTT polymer. Optimisation of the polymer solution and deposition are highlighted, to develop thin-films in OFETs. Receptor functionalisation, capitalising on strain-promoted azide-alkyne click chemistry, was explored. Morphology, modified surface chemistry and OFET performance were investigated. Additionally, research on the development of an organic electrochemical transistor (OECT), fabricated on a flexible substrate is presented. A novel dithienopyrrole (DTP) derivative, endowed with a carboxyl group, was utilised as the channel material upon electropolymerisation. A receptor functionalisation strategy is discussed. Morphology, modified surface chemistry and OECT performance were investigated. The strategies presented can enable the optimisation of organic transistor biosensors, further bridging a reality where such devices are integrated into medicine. As research in this field progresses, the integration of biosensors into medicine will significantly enhance the efficiency and accuracy of diagnostics, paving the way towards personalised and timely healthcare