Dissertations / Theses on the topic 'Dielectric polymers'
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1
Akins, Robert Benjamin. "Dielectric investigation of double glass transitions in polymers." Case Western Reserve University School of Graduate Studies / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1055878455.
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Zhong, Zhengzhong. "Dielectric relaxations in side-chain liquid crystalline polymers." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1060624225.
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Gupta, Sahil. "Structure-Property Relationships in Polymers for Dielectric Capacitors." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1395682393.
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Grove, Nicole R. "Characterization of functionalized polynorbornenes as interlevel dielectrics." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/11204.
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Riedel, Clément. "Dielectric and mechanical properties of polymers at macro and nanoscale." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20073.
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Le but de cette thèse était tout d'abord de comprendre les théories physiques qui décrivent la dynamique des polymères à l'échelle macroscopique. Le modèle de Rouse et la théorie d'enchevêtrement de De Gennes décrivent la dynamique des polymères non enchevêtrés et enchevêtrés, respectivement. Nous avons étudiés les différentes transitions entre ces deux régimes en utilisant deux techniques expérimentales: Broadband Dielectric Spectroscopy (BDS) et rhéologie. Les effets d'enchevêtrement sur les spectres diélectriques ont été discutés. Un test complet du modèle de Rouse à été effectué sur en comparant les prédictions de ce modèle pour la dépendance en fréquence de la permittivité diélectrique et du module de cisaillement aux données expérimentales. Ensuite nous avons développés des méthodes bas"s sur la microscopie à force électrostatique afin d'étudier les propriétés diélectriques locales. En utilisant la simulation numérique de la Méthode des Charges Equivalentes la constante diélectrique a été quantifiée à partir de la mesure du gradient de force crée par un potentiel statique entre une pointe et un diélectrique. Cette méthode permet d'imager la constante diélectrique avec une résolution spatial de 40 nm. Le retard de phase de la composante en 2ω de la force ou du gradient de force crée par un voltage alternatif est relié aux pertes diélectriques. En mesurant cette quantité nous avons montré que la dynamique était plus rapide proche d'une interface libre et nous avons développé un mode d'imagerie des pertes diélectriques. Cette méthode simple pourrait être appliqué en biologie ou matière molle en générale afin d'étudier des variations locales de constantes diélectriquesThe aim of this thesis was first to understand the physical theories that describe the dynamics of linear polymers at the macroscopic scale. Rouse and the reptational tube theory describe the large scale dynamics of unentangled and entangled polymers respectively. Using Broadband Dielectric Spectroscopy (BDS) and rheology we have studied the different transition between these two regimes. Effects of entanglement on dielectric spectra will be discussed (Rheologica Acta. 49(5):507-512). Avoiding the segmental relaxation contribution and introducing a distribution in the molecular weight we have been able to perform a comparison of the Rouse model with experiment dielectric and rheological data (Macromolecules 42(21): 8492-8499) Then we have developed EFM-based methods in order to study the local dynamics. Using the numerical simulation of the Equivalent Charge Method, the value of the static dielectric permittivity has been quantified from the measurement of the force gradient created by a VDC potential between a tip and a grounded dielectric (Journal of Applied Physics 106(2):024315). This method allows a quantitative mapping of dielectric properties with a 40 nm spatial resolution and is therefore suitable for the study of nano-defined domains (Physical Review E 81(1): 010801). The electrical phase lags in the 2ω components of the force or force gradient created by VAC voltage, ΔΦ2ω, are related with dielectric losses. Measuring the frequency dependence of ΔΦ2ω Crieder et al (Applied Physics Letters 91(1):013102) have shown that the dynamics at the near free surface of polymer films is faster than the one in bulk. We have used this method in order to visualize the activation of the segmental relaxation with temperature and frequency (Applied Physics Letters 96(21): 213110). All this measurements can be achieved using standard Atomic Force Microscope (and a lock-in) for VAC measurements
6
Nass, Kirk A. "Dielectric thermal analysis of polymeric matrices /." Thesis, Connect to this title online; UW restricted, 1989. http://hdl.handle.net/1773/9897.
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Warner, Nathaniel A. "Investigation of the Effect of Particle Size and Particle Loading on Thermal Conductivity and Dielectric Strength of Thermoset Polymers." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849629/.
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Semiconductor die attach materials for high voltage, high reliability analog devices require high thermal conductivity and retention of dielectric strength. A comparative study of effective thermal conductivity and dielectric strength of selected thermoset/ceramic composites was conducted to determine the effect of ceramic particle size and ceramic particle loading on thermoset polymers. The polymer chosen for this study is bismaleimide, a common aerospace material chosen for its strength and thermal stability. The reinforcing material chosen for this study is a ceramic, hexagonal boron nitride. Thermal conductivity and dielectric breakdown strength are measured in low and high concentrations of hexagonal boron nitride. Adhesive fracture toughness of the composite is evaluated on copper to determine the composite’s adhesive qualities. SEM imaging of composite cross-sections is used to visualize particle orientation within the matrix. Micro-indentation is used to measure mechanical properties of the composites which display increased mechanical performance in loading beyond the percolation threshold of the material. Thermal conductivity of the base polymer increases by a factor of 50 in 80%wt loading of 50µm hBN accompanied by a 10% increase in composite dielectric strength. A relationship between particle size and effective thermal conductivity is established through comparison of experimental data with an empirical model of effective thermal conductivity of composite materials.
8
Eusner, Thor. "Determining the Preston constants of low-dielectric-constant polymers." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36308.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaf 30).
An important step in the manufacture of integrated circuits (ICs) is the Chemical Mechanical Polishing (CMP) process. In order to effectively use CMP, the removal rates of the materials used in ICs must be known. The removal rate of a given material by CMP can be determined once its Preston constant is known. The objectives of this work were to develop a method to determine the Preston constants and to measure the Preston constants of four low-dielectric-constant (low-k) polymers, labeled A, B, C, and D, and Cu. A weight-loss method, which measures the weight difference between the initial wafer and the polished wafer, provided repeatable results. The Preston constants ranged from 1.01 to 5.96 x10-'3 m2/N. The variation in measurements of the Preston constant ranged from 16% to 31%. The Preston constant of Cu was found to be 1.60 + 0.50 x10-13 m2/N. Of the four polymers, Polymer A had the smallest Preston constant, 1.01 i- 0.30 x10-13 m2/N. It was also determined that there is an approximate inverse linear relationship between the Preston constant of the four low-k polymers and their Young's moduli of elasticity. An approximate inverse linear relationship between the Preston constant of the four low-k polymers and the hardness was also observed.
by Thor Eusner.
S.B.
9
Xiao, Zhang. "PROBING POLYMER DYNAMICS USING HIGH THROUGHPUT BROADBAND DIELECTRIC SPECTROSCOPY." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1533127319642101.
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Maistros, G. M. "Dielectric monitoring during the cure of epoxy resin blends." Thesis, Cranfield University, 1991. http://dspace.lib.cranfield.ac.uk/handle/1826/10403.
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Dielectric monitoring and supporting techniques (differential
Scanning calorimetry, infra-red spectrosoopy, viscometry, dynamic
mechanical thermal analysis and light transmittance) were used to
study the isothermal cure reaction of the CTBN
rubber modified
DGEBA resin/amine hardener blends. The neat system was also
examined for the required knowledge of the matrix properties. The
complexity of the cure kinetics was demonstrated by the use of a
rapid technique for kinetic parameters evaluation.
The utility of the dielectric cure
monitoring is focused at the
observation of evidence o phase separation, gelation and
vitrification. The phase separatlon which the blends underwent
during the cure was detected by the dielectric »monitoring through
a
permittivity increase at the low frequency
response. The onset
of the rapid viscosity increase leading to gelation was also
indicated by the sharp decrease o the dielectric constant atlhigh
frequencies. The frequency dependence of the times reach the
dielectric loss peaks was used to predict successfully the
vitrification
times during the isothermal reactions o the blends.
The in-situ nature o the technique and the basic
understanding o the features appearing in the dielectric signal
during the cure reaction provide the basis for the
use of dielectric
monitoring in the process of composite
materials, manufacture.
11
Walmet, Eric Robert. "In-situ monitoring of PMMA solution polymerization with dielectric microsensors." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/10036.
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Doyle, S. E. J. "The physical characteristics and dielectric behaviour of cellulose acetate polymers." Thesis, University of Strathclyde, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371938.
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Romeo, Michael Joseph. "Design, synthesis, and characterization of novel, low dielectric, photodefinable polymers." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24782.
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Thesis (Ph.D.)--Chemical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Henderson, Cliff; Committee Member: Beckham, Haskell; Committee Member: Hess, Dennis; Committee Member: Koros, William; Committee Member: Tolbert, Laren.
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Norris, Ann Marie Walstrom. "Dielectric studies of novel polymeric systems." Diss., Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/53656.
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This work combines many characterization techniques in an effort to enhance understanding of molecular motions of polymers and. how they are influenced by' structure. The primary characterization method was dielectric spectroscopy which utilizes an AC electric field as the stress field.
A variety of new, well controlled polymeric systems were studied. The first series included a number of radial starblock copolymers, styrene/isoprene, t-butyl- styrene/isoprene, and t-butyl-styrene/butadiene. These ABA copolymers consisted of hard and soft blocks, with the soft block comprising 75% by weight. The effect of microstructure of the soft block, casting solvent, hydrogenation, and chemical composition of the hard block were some of the variables studied. The amount of phase separation and the molecular motions occurring will be influenced by these parameters. Hydrogenation of the soft block increased the phase separation.
Another system investigated included some stereospecific poly(alkyl methacrylates) which were synthesized anionically. In this series the alkyl group was systematically changed in order to study the effects of the bulkiness of the substituent and the tacticity on the a and ß transitions. The ß transition associated with side chain rotations was only observed in the case of the methyl and ethyl substituents. The Havriliak-Negami data analysis was used to evaluate the breadth and the skewness of the distribution of relaxation times.
Finally, some high temperature thermoplastic polymers were evaluated with dielectric spectroscopy. The effect of the backbone composition, moisture, and fillers on the β transition was looked at. These studies showed that moisture and fillers play an important role on the magnitude and temperature of the observed β transition.Ph. D.
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Wang, Jingsong Johari G. P. "Thermodynamics of polymerization, dielectric properties, and a new orientational glass /." *McMaster only, 2003.
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16
Sinno, Bilal. "Mechanical and dielectric characterization of electronic grade polymers at subambient temperatures." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/10149.
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Ratnam, Mamatha D. "Correlation between the dielectric, rheological and structural properties of DGEBA-DDS epoxy." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/10203.
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Simpson, Joycelyn Ovetta. "Structure-dielectric property relationships for epoxy systems : a free volume analysis." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/10102.
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Troutman, Tia Shawana. "Development of low viscosity, high dielectric constant polymers for integral passive applications." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/8683.
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Bergman, David. "The Effect of Partial Discharge Aging on the Dielectric Response of Polymers." Thesis, KTH, Elektroteknisk teori och konstruktion, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-157323.
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This work investigated the effect of partial discharges (PD) on the complex permittivity of PVC, PC, PTFE, PE and PA6. The material samples were subjected to prolonged PD activity and the complex permittivity of the material was measured by dielectric spectroscopy (DS) before and after the sample was aged. The results showed a change in the loss factor for the tested materials, some were more affected than others and showed different behaviors when subjected to the PD aging. Hence it was not possible to find any general trend in the complex permittivity of the tested materials. Several of the materials exhibited a loss factor with -1/2 slope at low frequencies corresponding to diffusion. The -1/2 slope implies that the loss factor and the dynamic component of the real permittivity should be equal, which could not be seen. Therefore it is uncertain whether what was observed is a diffusion process or not. The results could suggest that PD aging causes a change in the trapping characteristics of the material. Furthermore, space charges deposited on the cavity wall from the PD activity could diffuse into the bulk of the material where some of the charges are trapped. If a DS measurement is performed before the trapped charges have had time to recombine or be conducted away, it could affect the complex permittivity. This was demonstrated by performing another DS measurement on an aged PC sample which had been left to rest for 35 days. The measurement showed that the complex permittivity had returned to almost the same state as before aging. Measurement problems were encountered which affected the measurements in this work. The problems are believed to be caused by the measurement electrodes used for the DS measurements not being heavy enough to eliminate small unwanted air-gaps between the electrodes and sample. Furthermore, incomplete results were obtained for some measurements which was believed to be due to the capacitance of the sample being at the limit of what the measurement instrument was able to measure.Det här arbetet undersökte effekten av partiella urladdningar (PD) på den komplexa permittiviteten i PVC, PC, PTFE, PE och PA6. Materialproverna utsattes för långvarig PD aktivitet och materialets komplexa permittivitet mättes med hjälp av dielektrisk spektroskopi (DS) före och efter att provet åldrats. Resultaten visade en förändring i förlustfaktorn i de testade materialen, några påverkades mer än andra och de uppvisade olika beteenden när de blev utsatta för PD åldring. Det var därför inte möjligt att hitta någon generell trend i den komplexa permittiviteten för de olika testade materialen. Flera av materialen uppvisade en förlustfaktor med -1/2 lutning vid låga frekvenser vilket motsvarar diffusion. -1/2 lutningen medför att förlustfaktorn och den dynamiska komponenten av den reella permittiviteten borde sammanfalla, vilket inte kunde ses. Det är därför osäkert huruvida det som observerats är en diffusionsprocess eller inte. Resultaten kan tyda på att PD-åldring orsakar en förändring i potentialfällors egenskaper i materialet. Således skulle rymdladdningar som deponeras på väggarna i kaviteten på grund av PD-aktiviteten kunna diffundera in i materialet där en del av laddningarna fastnar. Om en DS mätning görs innan de fångade laddningarna har fått tillräcklig tid att rekombinera eller ledas iväg, kan det påverka den komplexa permittiviteten. Detta visades genom att genomföra en DS mätning på ett åldrat prov av PC som fått vila i 35 dagar. Mätningen visade att den komplexa permittiviteten hade återgått till nästan samma tillstånd som innan den åldrades. Mätproblem påträffades vilket påverkade mätningarna i detta arbete. Problemen antas vara orsakade av att mätelektroderna som användes till DS mätningarna inte var tillräckligt tunga för att eliminera små oönskade luftgap mellan elektroderna och provet. Dessutom erhölls ofullkomliga resultat för några av mätningarna vilket tros bero på att provets kapacitans befann sig på gränsen för vad mätinstrumentet kunde mäta.
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Appello, Mario. "Real-time measurement of electrical properties during the processing of conductive polymers." Thesis, University of Warwick, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341559.
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Houachtia, Afef. "Dielectric investigations on attograms and zeptograms of matter." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI006/document.
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Les recherches sur des attogrammes (1 attogramme = 10 -18 gramme) et zeptogrammes (1 zeptogramme = 10-21 gramme) de matière offrent la possibilité de mettre en évidence la transition entre la nanoscience et la physique des molécules, ouvrant la porte à des questions fondamentales en physique de la matière molle, comme par exemple ‘’Quelle est la quantité minimale de matière nécessaire pour ‘‘définir’’ les propriétés des matériaux ?’’. Les propriétés électriques et diélectriques des matériaux, à cette échelle, sont étudiées par la spectroscopie diélectrique. Cette technique offre une large gamme de fréquence, pour mesurer les propriétés diélectriques des matériaux, couvrant plus de 10 ordres de grandeur et allant de 10-3 à 10+7 Hz. Cette technique assure une caractérisation précise d’une grande diversité des phénomènes physiques qui se déroulent à des échelles de longueur et de temps différents, tels que: les transitions des phases, les fluctuations de densité, les fluctuations moléculaires, le transport des charges, etc. Les mesures à l’échelle des attogrammes et zeptogrammes nécessitent l’utilisation des cellules ayant des dimensions nanométriques. Basé sur le concept d’utiliser des nano-conteneurs comme des cellules expérimentales, un développement expérimental a été mis en évidence, dans cette thèse, permettant d’étudier la dynamique moléculaire et les transitions des phases des matériaux polymères, allant jusqu’au zeptogrammes de matière. Cette approche permet de cristalliser des très petites quantités des matériaux sous l’application d’un champ électrique élevé, dans le but d’induire une cohérence macroscopique des fonctions moléculaires. Cela peut donner lieu à des nouvelles propriétés des matériaux, qui n’existent pas dans le cas des matériaux en masseDielectric investigations on attograms (1 attogram = 10 -18 gram) and zeptograms of matter (1 zeptogram = 10 -21 gram) offer the possibility of exploring the transition between nanoscience and molecule physics, opening the door for fundamental questions in soft-matter physics, such as for instance “What is the minimum amount of matter necessary to “define” the material properties?”. The electric and dielectric properties of materials at this level are investigated by Broadband Dielectric Spectroscopy. This technique provides an extraordinary broad frequency range, for measuring dielectric properties of matter, covering more than 10 orders of magnitude, typically from 10-3 to 10+7Hz. It ensures a precise characterization of large diversity of physical phenomena taking place at different length and time scales such as: phase transitions, density fluctuations, molecular fluctuations, charge transport processes, etc. Measurements on the scale of attograms and zeptograms require sample cells having all three dimensions on the nanometric length-scale. Based on the concept of employing nanocontainers as experimental cells, a novel experimental development allowing investigations on molecular dynamics and phase transitions of polymeric materials down to the level of zeptograms is demonstrated in the present PhD study. This approach enables one to crystallize tiny amounts of matter under high electric fields with the goal of inducing a macroscopic coherence of molecular functionalities. This could give rise to new material properties, not naturally available in the case of bulk materials
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Stevens, Derrick. "Molecular Dynamics in Self-assembled Monolayers and Polymers studied via sensitive Dielectric Spectroscopy." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-07052009-111325/.
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For many molecular systems, interpreting experimental molecular dynamics, by studying the response of a system to external stimuli, is a difficult task. Often the experimental response cannot be reasonably connected to a specific molecular motion. The aim of this work is to examine molecular systems where this difficulty can be overcome. We use sensitive dielectric spectroscopy to investigate the molecular dynamics of two different systems, chlorosilane self-assymbled monolayers and modified siloxane polymers. The polymers studied responded to changes in their surrounding media by altering their wetting characterstics. Because this macroscopic responsive is present, we are able correlate the microscopic response (as measured by dielectric spectroscopy) to likely molecular motions. The goal of the self-assembled monolayer work is similar albeit by a different approach. In this case, the degrees of freedom were limited by using surface bound molecules. By controlling the molecular density we are able to investigate both local, non-cooperative motions as well as interacting dynamics. Specifically, we will show a connection between the interacting dynamics of the self-assembled monolayers to glass transitions found in more complicated materials.
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Hegde, Vikas. "Etudes diélectriques des matériaux biodégradables et/ou bio-sourcés." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT031/document.
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L'utilisation extensive des combustibles fossiles, l'émission de gaz à effet de serre dans l'atmosphère et les difficultés de recyclage des résidus de consommation incitent au recours accru aux polymères biodégradables. Dans le domaine du génie électrique, de nombreux polymères trouvent des applications dans les systèmes d'isolation des matériels électriques. Ces polymères sont issus du pétrole, peu respectueux de l'environnement et la plupart d'entre eux ne sont pas biodégradables. Dans le but de les remplacer, des polymères biodégradables ont été explorés.Une revue des travaux de recherche sur les polymères biodégradables dans le domaine du génie électrique a été réalisée. Les propriétés thermiques et électriques de polymères biodégradables et conventionnels sont rapportées et comparées.Les polymères biodégradables et / ou biosourcés sélectionnés et mis en œuvre sont le Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), le polycaprolactone (PCL) et l’acide polylactique PLA. Un matériau nanocomposite basé sur PLA a également été préparé. Les propriétés diélectriques pour une large gamme de température et de fréquence ont été mesurées par spectroscopie diélectrique et analysées en s’appuyant sur les propriétés thermiques obtenues par DSC et DMA. La résistivité volumique et la tenue diélectrique ont pu également être mesurées. Ces polyesters biodégradables sont comparés aux polymères conventionnelsThe declining resources of fossil fuels, increase in wide-spread pollution, emission of green-house gases and difficulties in recycling waste materials are pushing biodegradable polymers into prominence. In the domain of electrical engineering, many polymers find applications in various electrical insulation systems. These polymers are petro-based, not eco-friendly and most of them are not biodegradable. With an objective to replace conventional products, biodegradable polymers are explored for their dielectric properties.In this work, a detailed study on the present status in the research work on biodegradable polymers in the electrical engineering domain is presented. Thermal and electrical properties of both biodegradable and classical polymers are compiled and compared.The polymers processed and studied were Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), Polycaprolactone (PCL), Poly(lactic acid) (PLA) and PLA based nanocomposite. Dielectric properties for a wide range of temperature and frequency were measured by dielectric spectroscopy and analyzed with the help of DSC and DMA experiments. Volume resistivity and electrical breakdown were measured on few polymers. These biodegradable polyesters were compared with conventional polymers
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Kunal, Kumar. "Influence of Chemical Structure and Molecular Weight on Fragility in Polymers." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1247855648.
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Chen, Xinyue. "Understanding Loss Mechanisms and Enhancing Dielectric Properties of Multilayer Polymer Films for Capacitor Applications." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1584527483998243.
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Wang, Chunlai. "AZADIPYRROMETHENE-BASED N-TYPE ORGANIC SEMICONDUCTORS AND HIGH DIELECTRIC CONSTANT POLYMERS FOR ELECTRONIC APPLICATIONS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case156708229609051.
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Kanbur, Yasin. "Conductive Polymer Nanocomposites Of Polypropylene And Organic Field Effect Transistors With Polyethylene Gate Dielectric." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613312/index.pdf.
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One of the aim of this study is to prepare conductive polymer nanocomposites of polypropylene to obtain better mechanical and electrical properties. Composite materials based on conductive fillers dispersed within insulating thermoplastic matrices have wide range of application. For this purpose, conductive polymer nanocomposites of polypropylene with nano dimentional conductive fillers like carbon black, carbon nanotube and fullerene were prepared. Their mechanical, electrical and thermal properties were investigated.
Polypropylene (PP)/carbon black (CB) composites at different compositions were prepared via melt blending of PP with CB. The effect of CB content on mechanical and electrical properties was studied. Test samples were prepared by injection molding and compression molding techniques. Also, the effect of processing type on mechanical and electrical properties was investigated. Composites become semiconductive with the addition of 2 wt% CB.
Polypropylene (PP) / Carbon Nanotube (CNT) and Polypropylene / Fullerene composites were prepared by melt mixing. CNT&rsquos and fullerenes were surface functionalized with HNO3 : H2SO4 before composite preparation. The CNT and fullerene content in the composites were varied as 0.5, 1.0, 2.0 and 3.0 % by weight. For the composites which contain surface modified CNT and fullerene four different compatibilizers were used. These were selected as TritonX-100, Poly(ethylene-block-polyethylene glycol), Maleic anhydride grafted Polypropylene and Cetramium Bromide. The effect of surface functionalization and different compatibilizer on mechanical, thermal and electrical properties were investigated. Best value of these properties were observed for the composites which were prepared with maleic anhydride grafted polypropylene and cetramium bromide. Another aim of this study is to built and characterize transistors which have polyethylene as dielectric layers. While doing this, polyethylene layer was deposited on gate electrode using vacuum evaporation system. Fullerene , Pentacene ve Indigo were used as semiconductor layer. Transistors work with low voltage and high on/off ratio were built with Aluminum oxide - PE and PE dielectrics.
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Pušec, Daniel. "Účinky vlhkosti na elektrické vlastnosti silikonového kaučuku." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-242853.
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At the beginning, this master thesis briefly describes the principle of semiconductors. It states their types, methods of operation, fields of use, and it interprets the manner of semiconductor devices’ passivation. Then it introduces silicones, their properties and usage. Later on, this thesis summerize air humidity theory and materiál moisturing including mathematical interpretation. Next chapter is devoted to basics of dielectric materials’ behavior. And finally, the last part of this thesis estimates charakteristics of passivation materiál, Dow Corning HIPEC Q1-9205 silicone rubber.
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Rao, Yang. "High dielectric constant materials development and electrical simulation of embedded capacitors." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/20014.
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Kerr, Maria. "The grafting of collagen to medically relevant polymers through an atmospheric pressure dielectric barrier discharge." Thesis, University of Ulster, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.536466.
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Andersen, Allen. "The Role of Recoverable and Non-Recoverable Defects in DC Electrical Aging of Highly Disordered Insulating Materials." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7047.
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Electrical insulation under high voltage can eventually fail, causing critical damage to electronics. Such electrostatic discharge (ESD) is the primary source of anomalies or failures on spacecraft due to charged particles from the Sun or planetary radiation belts accumulating in spacecraft insulators. Highvoltage direct current power distribution is another example of a growing industry that needs to estimate the operational lifetime of electrical insulation. My research compares laboratory tests of ESD events in common insulating materials to a physics-based model of breakdown. This model of breakdown is based on the approximation that there are two primary types of defects in structurally amorphous insulators. One of the two defect modes can switch on and off depending on the material temperature. This dual-defect model can be used to explain both ESD and less-destructive transient partial discharges. I show that the results of ESD tests agree reasonably well with the dual defect model. I also show that transient partial discharges, which are usually ignored during ESD tests, are closely related to the probability of catastrophic ESD occurring. Since many partial discharges are typically seen during one ESD test, this relationship suggests that the measurements of partial discharges could accelerate the testing needed to characterize the likelihood of ESD in insulating materials.
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Mackey, Matthew. "Enhanced Dielectric Properties of Micro and Nanolayered Films for Capacitor Applications." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1333479475.
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Rajarathinam, Venmathy. "Imprint lithography and characterization of photosensitive polymers for advanced microelectronics packaging." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34722.
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To enable fast and reliable processors, advances must be made in the interconnections on the printed circuit board and in the interconnections from the chip to the printed circuit board. Processing techniques have been demonstrated to fabricate a copper-clad encapsulated air dielectric layer to enable low loss off-chip electrical signal lines using sacrificial polymers and the three dimensional patterning capabilities of imprint lithography. The inclusion of an air gap can eliminate the dielectric loss allowing the signal to propagate over longer lengths. Additionally, the low dielectric constant of air lowers the loss contributions from the conductor and increases the signal propagation velocity reducing delay. The metal shielding could minimize the crosstalk noise and radiation losses that are significant at high frequencies. The three dimensional patterning capabilities of imprint lithography fabricated curved structures and rounded terminations which can reduce reflections at discontinuities. Furthermore, imprint lithography also created planarized surfaces which simplified the buildup process. Since imprint lithography, only uses temperature and pressure to make a pattern it is an inexpensive and simple process advancement. The metal-clad encapsulated air dielectric structures were fabricated in a comparable number of registration steps to traditional transmission lines.
Implementation of all copper chip to substrate interconnects would provide high conductivity electrical connections, resistance to electromigration while avoiding formation of brittle intermetallics. High aspect ratio polymer molds for copper electroplating interconnects could enable improved integrated circuit electrical performance. The properties of a new aqueous base develop, negative-tone photosensitive polynorbornene polymer have been characterized to develop mechanically compliant all copper connections between the chip and printed circuit board. High aspect ratio features of 7:1 (height:width) were produced in 70 ìm thick films in a single coat with straight side-wall profiles and high fidelity. The polymer films studied had a contrast of 11.6 and a low absorption coefficient. To evaluate the polymer's suitability to microelectronics applications, epoxy cross-linking reactions were studied as a function of processing condition through Fourier transform infrared spectroscopy, nano-indentation, and dielectric measurements. The fully cross-linked films had an elastic modulus of 2.9 GPa and hardness of 0.18 GPa which can improve the mechanical compliance of the copper interconnections.
A photo-imprint lithography process was developed to improve the photo-patterning of the polynorbornene polymer for high aspect ratio hollow structures. A shallow photo-imprint stamp was developed to physically displace material in the polymer core. Since the imprint stamp displaces material in the area of the feature, the effective film thickness is reduced compared to the bulk film. The reduction in film height reduced the effects of scattering in the core and also facilitated transport of developer within the core. The photo-imprint lithography process resulted in high aspect ratio hollow core pillars that exceeded optical resolution capabilities for comparable feature sizes.
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Liu, Tao. "Determination of three dimensional refractive indices and absorption coefficients of anisotropic polymer films with prism wave-guide coupler." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/8601.
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Su, Ruo Qing. "New composite material based on silsesquioxane polymers and nanoporous particles for low-k [low-kappa] dielectric application." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972240519.
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ARAMBULO, PABLO CESAR SERRANO. "INVESTIGATION OF DIELECTRIC LAYER FOR THE DEVELOPMENT OF ORGANIC FIELD EFFECT TRANSISTORS (OFET) BASED ON CONJUGATED POLYMERS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=33715@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Nos últimos anos, polímeros conjugados ganharam muita atenção na eletrônica orgânica por seu uso na fabricação de dispositivos flexíveis e de baixo custo. Como resultado, diferentes tipos de dispositivos têm sido desenvolvidos como: diodos emissores de luz orgânicos (OLEDs), células fotovoltaicas orgânicas (OPVs) e transistores de efeito de campo orgânicos (OFETs). Em particular, para os OFETs seu desempenho depende da interface isolante/semicondutor, principalmente, devido ao acúmulo de portadores de carga. Além disso, as propriedades da interface afetam fortemente o transporte de carga através do canal de dispositivo. Por estas razões, a pesquisa de novos polímeros semicondutores e novos materiais dielétricos é um fator chave para aprimorar o desempenho dos dispositivos. Neste trabalho, os polímeros PMMA, PVA, FORMVAR e PU foram investigados como materiais dielétricos. Inicialmente foram fabricados capacitores de placas planas paralelas do tipo ITO/dielétrico/Al para determinar a constante dielétrica dos isolantes, as curvas JxV e a capacidade por unidade de área. Desenvolveu-se OFETs tipo Top-Gate/Bottom-Contacts (TGBC) com a estrutura Au/P3HT/PMMA/Ag e Au/P3HT/PU/Ag. No trabalho, a espessura dos dielétricos foi variada para aprimorar o desempenho dos dispositivos. Para os OFETs de PMMA obteve-se resultados concordantes com os da literatura. Os novos OFETs de PU apresentaram tensões de operação menores que 5V, que é um requisito para a integração destes OFETs em aplicações da eletrônica orgânica. A mobilidade obtida nestes OFETs de PU foi de 1.25 cm(2)/V.s, com uma tensão limiar de 0.02 e uma razão On/Off de 100.
In the last years, conjugated polymers have received much attention in organic electronics for their use in the fabrication of low cost and flexible devices. As a result, different types of devices have been developed e.g. organic light emitting diodes (OLEDs), photovoltaic devices (OPVs) and field effect transistors (OFETs). For the OFETs in particular, their performance depends primarily on insulator/semiconductor interface, mainly due to charge carrier accumulation. Moreover, the interface properties strongly affect the charge transport through the device channel. For these reasons, the research for new semiconductor polymers and new dielectric materials is key to advancing the performance improvement of devices. In this work, the polymers PMMA, PVA, FORMVAR and PU were used as dielectric materials. Initially, parallel plate capacitors of the structure ITO/dielectric/A1 were made, in order to determine the dielectric constant of the insulators, get the curves JxV and the capacity per unit area. It was used to develop Top-Gate/Bottom-Contacts (TGBC) OFETs with structures of Au/P3HT/PMMA/Ag and Au/P3HT/PU/Ag. The thicknesses of the dielectric materials were varied to improve the performance of the devices. For the PMMA OFETs, the results obtained were concordant with those of the existing literature. The new PU OFETs presented with operating voltages of less than 5V, appropriate for applications of these OFETs in organic electronics. The mobility of the PU OFETs was 1.25cm(2)/V.s, the threshold voltage 0.02V and the On/Off ratio 100.
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Pejic, Sandra. "Structure-Property Studies of Substituted Azadipyrromethene-Based Dyes and High Dielectric Constant Polymers for Organic Electronic Applications." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1527949734211196.
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Mohomed, Kadine. "Thermal analyses of hydrophilic polymers used in nanocomposites and biocompatible coatings." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001442.
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Cabral, Flávio Pandur Albuquerque. "Medidas das constantes dielétricas e deslocamento elétrico em dielétricos: desenvolvimento da técnica e metodologia." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-08042014-151001/.
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Desenvolveu-se um sistema para medir a constante dielétrica complexa de amostras dielétricas, de construção simples, versátil e de baixo custo. A medida é feita aplicando-se uma tensão senoidal e fazendo-se a aquisição do sinal aplicado e do sinal da resposta elétrica (carga elétrica). Emprega-se uma placa A/D para a aquisição de dados com taxa de amostragem de 100 Ksamples/seg e através da transformada de Fourier discreta destes sinais determina-se a impedância complexa da amostra, a partir da qual calcula-se a constante dielétrica complexa. A placa utilizada e o circuito de medida da carga elétrica introduzem defasagens indesejáveis nos sinais, cujas correções são feitas através de programa no computador usado para aquisição dos sinais. O sistema mostra um desempenho similar àqueles dos equipamentos comerciais para freqüências no intervalo de 0,1H.z a 1KHz, sendo testado com componentes resistivos e capacitivos e posteriormente em amostras de Teflon FEP, poli(fluoreto de vinilideno) e seus copolímeros com trifluoretileno. O sistema também foi utilizado para medir o deslocamento elétrico nos polímeros ferroelétricos sob a aplicação de campos elevados. Neste caso determinaram-se as curvas de histerese dielétrica e os deslocamentos de primeira, segunda e terceira ordem.A low cost and a simple experimental system for measuring the complex dielectric constant of dielectric samples were developed. Measurements were performed measuring the electric charge response resulting from the application of a sinusoidal voltage. The system was based on an A/D acquisition board with sampling rate of 100 Ksamples/sec. The complex impedance was calculated using the discrete Fourier transform from which the complex dielectric constant was found. The phase differences introduced by the A/D board and the amplifiers circuits were connected by software. The setup showed that the results are comparable to that ones obtained with commercial impedance analyzers in the range of frequencies between 0.1 Hz and 1 KHz. Such measurements were obtained using resistors and/or capacitors and also using samples of Teflon FEP, PVDF and its copolymers with trifluorethylene. The setup was also capable to measure the electric displacement in ferroelectric polymers submitted to high fields. Hysteresis loops and the nonlinear electric displacement of first, second and third order were measured.
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Tseng, Jung-Kai. "Enhanced Dielectric Properties of Multilayer Capacitor Film via Interfacial Polarization." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1449137228.
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Spencer, Todd Joseph. "Air-gap transmission lines on printed circuit boards for chip-to-chip interconnections." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34754.
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Low-loss off-chip interconnects are required for energy-efficient communication in dense microprocessors. To meet these needs, air cavity parallel plate and microstrip lines with copper conductors were fabricated on an FR-4 epoxy-fiberglass substrate using conventional microelectronics manufacturing techniques. Copper transmission lines were separated by a composite dielectric of air and Avatrel 2000P and by a dielectric layer of air only. The composite dielectric lines were characterized to 10 GHz while the all air dielectric lines were characterized to 40 GHz. The transmission line structures showed loss as low 1.5 dB/cm at 40 GHz with an effective dielectric constant below 1.4. These novel structures show low loss in the dielectric due to the reduced relative permittivity and loss tangent introduced by the air cavity.
Transmission line structures with a composite dielectric were built by coating the sacrificial polymer poly(propylene carbonate) (PPC) over a copper signal line, encapsulating with an overcoat polymer, electroplating a ground line, and decomposing PPC to form an air cavity. The signal and ground wires were separated by a layer of 15 µm of air and 20 µm of Avatrel 2000P. Air cavity formation reduced dielectric constant more than 30 percent and loss of less than 0.5 dB/cm was measured at 10 GHz.
Residue from PPC decomposition was observed in the cavity of composite dielectric structures and the decomposition characteristics of PPC were evaluated to characterize the residue and understand its formation. Analysis of PPC decomposition based on molecular weight, molecular backbone structure, photoacid concentration and vapor pressure, casting solvent, and decomposition environment was performed using thermogravimetric analysis and extracting kinetic parameters.
Novel interaction of copper and PPC was observed and characterized for the self-patterning of PPC on copper. Copper is dissolved from the surface during PPC spincoating and interacts with the polymer chains to improve stability. The improved thermal stability allows selective patterning of PPC on copper. Decomposition characteristics, residual metals analysis, and diffusion profile were analyzed. The unique interaction could simplify air-gap processing for transmission lines.
Inorganic-organic hybrid polymers were characterized for use as overcoat materials. Curing characteristics of the monomers and mechanical properties of the polymer films were analyzed and compared with commercially available overcoat materials. The modulus and hardness of these polymers was too low for use as an air-gap overcoat, but may be valuable as a barrier layer for some applications.
The knowledge gained from building transmission line structures with a composite dielectric, analyzing PPC decomposition, interaction with copper, and comparison of hybrid polymers with commercial overcoats was used to build air-gap structures with improved electrical design. The ground metal was separated from the signal only by air. The signal wire was supported from above using 60 µm of Avatrel 8000P as an overcoat. Structures showed loss of less than 1.5 dB/cm at 40 GHz, the lowest reported value for a fully encapsulated transmission line structure.
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Halethimmanahally, Thejaswini C. [Verfasser]. "Atmospheric-Pressure Dielectric Barrier Discharges: Synthesis and Deposition of Organic plasma polymers and their characterizations / Thejaswini C. Halethimmanahally." Greifswald : Universitätsbibliothek Greifswald, 2012. http://d-nb.info/1028455658/34.
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Murray, Christopher Ian. "The study of side chain organisation in liquid crystalline polymers using dielectric relaxation spectroscopy and X-ray diffraction." Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286908.
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Santos, Alessandro Luiz Ribeiro dos [UNESP]. "Estudo de polímeros comerciais tratados a plasma em pressão atmosférica." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/91830.
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Materiais poliméricos têm sido amplamente utilizados em várias áreas tecnológicas e biomédicas, devido às suas excelentes propriedades mecânicas, térmicas e elétricas. No entanto, estes materiais têm baixa energia de superfície e, portanto, não aderem facilmente a outros materiais. Por isso, para muitas aplicações é necessário modificar a superfície do polímero, a fim de aumentar a sua energia de superfície. Tratamentos a plasma à pressão atmosférica têm sido muito utilizados para modificar as propriedades superficiais de polímeros comerciais, devido aos baixos custos do processo. Este trabalho apresenta os resultados do tratamento de tereftalato de polietileno (PET), poliuretano (PU) e de politetrafluoretileno (PTFE) em plasma de descargas com barreira dielétrica (DBD) em ar, nitrogênio e argônio, à pressão atmosférica. As superfícies tratadas foram caracterizadas por medidas de ângulo de contato, espectroscopia de fotoelétrons de raios-X (XPS) e microscopia de força atômica (AFM). A superfície polimérica, modificada nas DBD a pressão atmosférica, mostraram uma redução significativa no ângulo de contato da água, embora uma recuperação parcial da molhabilidade ocorresse nos primeiros dias após o tratamento. Todavia, a recuperação foi insuficiente para que as amostras tratadas recuperassem a sua molhabilidade original. Análises de XPS mostraram um aumento na concentração de oxigênio na superfície, devido à formação de grupos polares, tais como C-O e OC= O. Um pequeno aumento na concentração de nitrogênio também foi observada. Imagens de AFM mostraram um aumento da rugosidade de polímeros tratados, decorrentes da interação física entre as espécies geradas na descarga e a superfície do polímero. A superfície ativada e a elevada tensão superficial dos polímeros tratados devem levar a um aumento da aderência do polímero.
Polymeric materials have been widely used in various biomedical and technological applications, due to their excellent mechanical, thermal and electric properties. However, these materials have low surface energy, and thus not easily adhere to other materials. Therefore, for many applications it is necessary to modify the polymer surface in order to increase its surface energy. Plasma treatments at atmospheric pressure have been frequently used to modify the surface properties of commercial polymers, due to their low process costs. This work reports the results of polyethylene terephthalate (PET), polyurethane (PU) and polytetrafluoroethylene (PTFE) treatments in plasma by dielectric barrier discharges (DBDs) in air, nitrogen and argon at atmospheric pressure. The plasma-modified surfaces were characterized by contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The polymer surface, modified by DBD at atmospheric pressure, showed a significant decrease in water contact angle although a partial recovery of the surface wettability occurred during the first few days after the treatment. However, the process of hydrophobic recovery was insufficient for complete recovering of the samples original wettability. XPS analysis showed an increase of the oxygen concentration on the surface, due to the formation of polar groups, such as C-O and OC= O. A small increase in the concentration of nitrogen was also observed. AFM images exhibit an increased roughness of the treated polymers because of the physical interaction between the species generated in the discharge and the polymer surface. The activated surface and high surface tension of treated polymers should promote an enhancement of the polymer adhesion to paints and coatings.
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Fiocco, Laura. "Silicate ceramics from preceramic polymers and fillers." Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424243.
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The topic of this research work deals with the synthesis, the characterization and the optimization of silicate ceramics, realized through the controlled pyrolysis of preceramic polymers filled with inorganic fillers.
According to this synthesis route, preceramic polymers can be used as silica precursors by virtue of their conversion from polymers to ceramics by thermal oxidative reactions. Besides the low cost, large availability and easy-handling of the preceramic polymers, a further advantage regards the fabrication of the final ceramic from the process point of view. In fact, the component can be easily shaped by means of the conventional plastic forming techniques, thanks to the polymeric nature of the system before cross-linking. These simple shaping techniques even include the realization of dense components, by warm/cold pressing, and of highly porous bodies, by direct 3-D printing or by foaming of preceramic slurries, before ceramization.
The incorporation of fillers, that generally can be passive or active, is considered one of the most effective strategies to decrease the shrinkage and the formation of macro-defects, that inevitably take place throughout the polymer-to-ceramic conversion, allowing the realization of relatively large components.
A novel approach concerning the use of reactive fillers consists, instead, in incorporating fillers as oxide precursors, that are intended to fully react with the ceramic residue of the polymeric precursors, rather than to compensate the shrinkage. As a result, these reactions between the preceramic polymers and the reactive fillers, occurring throughout the pyrolysis, lead to the formation of specific crystalline phases, that are generally not directly achievable by the simple pyrolysis of a preceramic polymer. Following this methodology, the present Ph.D. thesis has been devoted to an organic investigation of the applications that this strategy could offer, starting from silicone-based mixtures incorporating reactive fillers. By this route, the advantages connected with the presence of a polymeric phase, especially in the shaping step of the processing, can even be combined with the advantages related to the whole processing cycle of preceramic polymers, leading to the realization of ceramic components at relatively low temperatures (even below 1200 °C) and avoiding the conventional methodologies.
In this research work, the fillers incorporated in the preceramic mixtures have also been exploited as foaming agents or liquid phase formers, thus helping respectively the direct shaping in porous bodies or the obtainment of glass-ceramic components. However, as already mentioned, the main purpose of the fillers, here, is to serve as oxide precursors, in order to synthesize crystalline ceramics after pyrolysis of specific compositions, achievable by the reaction occurring between the ceramic residue of the polymeric precursor and the oxides coming from the thermal decomposition of reactive fillers. The type of fillers can be conveniently selected according to the desired final composition; therefore, a wide variety of ceramic systems can be achieved, simply by changing the proportions and composition of the starting polymers and fillers.
The first part of the following chapters will be focused on the realization of peculiar ceramic and glass-ceramic formulations, that are well known to have very pronounced biological properties, and in their shaping in suitable architectures for biomedical purposes, thus having applicability as bioceramics for bone regeneration implants. In fact, besides bioglasses, other bioceramic formulations have recently received a growing interest in the field of bone ingrowth, according to their ability to stimulate body tissues to repair themselves. The formulations developed in this research work mainly belong to the CaO-SiO2 or CaO-MgO-SiO2 oxides systems, but some crystalline phases have also been combined to obtain composite formulations, or have been coated with other materials (hydroxyapatite) exhibiting the same properties as natural bone from a chemical and structural point of view, to increase their bioactivity even more. In this framework, the developed materials have not only been characterized in terms of microstructure, mechanical and physical properties, but their biological behaviour has been assessed as well.
Then, exploiting the concept of multifunctionality characterizing some silicates, besides deep analogies in the crystal structure and in the processing route, it has been possible to establish a thread running between the above-discussed biosilicates and other silicates with other advanced functional applications. In accordance with this logic, the technology has been extended to dielectric, photoluminescent and refractory silicates.L’attività di ricerca presentata in questa tesi ha riguardato la sintesi, la caratterizzazione e l’ottimizzazione di ceramici silicatici, realizzati a partire dalla pirolisi controllata di polimeri preceramici caricati con fillers inorganici. Sulla base di tale metodo di sintesi, i polimeri preceramici possono essere utilizzati come precursori per l’ottenimento di silice in virtù della loro conversione da polimeri a ceramici tramite reazioni termo-ossidative. Oltre al basso costo, alla larga disponibilità e alla semplicità di utilizzo, un ulteriore vantaggio riguarda la fabbricazione del ceramico finale dal punto di vista del processo. Infatti, il componente può essere formato sfruttando le convenzionali tecniche di formatura per i materiali polimerici, sfruttando la presenza di una componente polimerica nel sistema prima di imporne la reticolazione. Tali semplici tecniche di formatura includono anche la realizzazione di componenti densi, tramite pressatura, o di corpi altamente porosi, tramite stampaggio 3-D diretto o schiumaggio delle miscele preceramiche, prima di ceramizzarle. L’inserimento di fillers, che generalmente si suddividono in attivi e passivi, è considerata una delle più efficaci strategie per ridurre il ritiro dimensionale e la formazione di macrodifetti, che inevitabilmente hanno luogo durante la conversione da materiale polimerico a ceramico, permettendo la realizzazione di componenti relativamente spessi. Un approccio più innovativo relativo all’uso di fillers reattivi, invece, riguarda l’introduzione di fillers come precursori di ossidi che possano reagire completamente con il residuo ceramico dei precursori polimerici, piuttosto che finalizzati a compensare il ritiro dimensionale dei componenti. Dalle reazioni tra i precursori polimerici e i fillers reattivi durante la pirolisi, risulta la formazione di fasi cristalline specifiche, che generalmente non sono ottenibili in modo diretto dal semplice trattamento termico dei precursori polimerici. Seguendo tale processo di sintesi, la presente tesi di dottorato ha avuto come obiettivo lo studio delle applicazioni che tale tecnica potrebbe offrire, partendo da miscele a base di polimeri siliconici caricati con filler reattivi. In questo modo, i vantaggi derivanti dalla presenza di una componente polimerica, sfruttati soprattutto in fase di formatura, possono anche essere combinati con i vantaggi offerti dall’intero ciclo produttivo di ceramici da polimeri preceramici, portando alla realizzazione di componenti ceramici a temperature abbastanza basse (entro i 1200 °C) e evitando i metodi di sintesi più convenzionali. Nel presento lavoro di ricerca, i fillers incorporati nelle miscele preceramiche sono anche stati sfruttati come agenti schiumanti o formatori di fase liquida, permettendo rispettivamente lo schiumaggio diretto di componenti altamente porosi in un caso e l’ottenimento di vetro-ceramiche nel secondo. Ad ogni modo, come già spiegato, il fine principale dell’uso dei fillers, qui, è stato il loro utilizzo come precursori di ossidi, in modo da permettere, dopo ceramizzazione, la sintesi di fasi ceramiche cristalline di specifica composizione, direttamente ottenibili dalla reazione tra il residuo ceramico dei precursori polimerici e gli ossidi provenienti dalla decomposizione termica dei fillers reattivi. La tipologia di fillers può essere adeguatamente modificata a seconda della composizione finale desiderata; di conseguenza, un’enorme varietà di sistemai ceramici può essere realizzata semplicemente modificando le proporzioni e la composizione dei polimeri e dei fillers di partenza. La prima parte dei capitoli seguenti sarà imperniata sulla realizzazione di particolari ceramici e vetro-ceramiche molto conosciuti per le loro pronunciate proprietà biologiche, oltre che sulla loro formatura in strutture adeguate in applicazioni biomedicali come impianti per rigenerazione ossea. Infatti, parallelamente ai biovetri, altre formulazioni bioceramiche hanno ricevuto recentemente un interesse crescente nel campo biomedicale, in virtù della loro capacità di stimolare i tessuti biologici ad auto-ripararsi. Le formulazioni qui sviluppate appartengono prevalentemente ai sistemi di ossidi del tipo CaO-SiO2 o CaO-MgO-SiO2, ma alcune fasi cristalline sono anche state combinate tra loro per ottenere formulazioni composite, oppure sono state rivestite con altri materiali, come l’idrossiapatite, esibenti proprietà simili a quelle dell’osso naturale sotto il punto di vista sia chimico che strutturale, al fine di incrementarne ulteriormente la bioattività. In questo contesto, i materiali sviluppati sono stati caratterizzati non solo dal punto di vista microstrutturale, meccanico e fisico, ma è stato studiato anche il loro comportamento sotto il profilo biologico. Inoltre, sfruttando il concetto di multifunzionalità che caratterizza alcuni silicati, oltre alle profonde analogie in termini di struttura cristallina e di caratteristiche di processo, è stato possibile stabilire un filo conduttore tra i biosilicati sopra menzionati e altri silicati con altre applicazioni funzionali avanzate. In quest’ottica, la tecnologia è stata estesa ad altri silicati caratterizzati da proprietà dielettriche, luminescenti e refrattarie.
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Carr, Joel Matthew. "CONFINED LAYERED POLYMERIC SYSTEMS FOR PACKAGING ANDCAPACITOR APPLICATIONS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1363104386.
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Santos, Alessandro Luiz Ribeiro dos. "Estudo de polímeros comerciais tratados a plasma em pressão atmosférica /." Guaratinguetá : [s.n.], 2010. http://hdl.handle.net/11449/91830.
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Resumo: Materiais poliméricos têm sido amplamente utilizados em várias áreas tecnológicas e biomédicas, devido às suas excelentes propriedades mecânicas, térmicas e elétricas. No entanto, estes materiais têm baixa energia de superfície e, portanto, não aderem facilmente a outros materiais. Por isso, para muitas aplicações é necessário modificar a superfície do polímero, a fim de aumentar a sua energia de superfície. Tratamentos a plasma à pressão atmosférica têm sido muito utilizados para modificar as propriedades superficiais de polímeros comerciais, devido aos baixos custos do processo. Este trabalho apresenta os resultados do tratamento de tereftalato de polietileno (PET), poliuretano (PU) e de politetrafluoretileno (PTFE) em plasma de descargas com barreira dielétrica (DBD) em ar, nitrogênio e argônio, à pressão atmosférica. As superfícies tratadas foram caracterizadas por medidas de ângulo de contato, espectroscopia de fotoelétrons de raios-X (XPS) e microscopia de força atômica (AFM). A superfície polimérica, modificada nas DBD a pressão atmosférica, mostraram uma redução significativa no ângulo de contato da água, embora uma recuperação parcial da molhabilidade ocorresse nos primeiros dias após o tratamento. Todavia, a recuperação foi insuficiente para que as amostras tratadas recuperassem a sua molhabilidade original. Análises de XPS mostraram um aumento na concentração de oxigênio na superfície, devido à formação de grupos polares, tais como C-O e OC= O. Um pequeno aumento na concentração de nitrogênio também foi observada. Imagens de AFM mostraram um aumento da rugosidade de polímeros tratados, decorrentes da interação física entre as espécies geradas na descarga e a superfície do polímero. A superfície ativada e a elevada tensão superficial dos polímeros tratados devem levar a um aumento da aderência do polímero.Abstract: Polymeric materials have been widely used in various biomedical and technological applications, due to their excellent mechanical, thermal and electric properties. However, these materials have low surface energy, and thus not easily adhere to other materials. Therefore, for many applications it is necessary to modify the polymer surface in order to increase its surface energy. Plasma treatments at atmospheric pressure have been frequently used to modify the surface properties of commercial polymers, due to their low process costs. This work reports the results of polyethylene terephthalate (PET), polyurethane (PU) and polytetrafluoroethylene (PTFE) treatments in plasma by dielectric barrier discharges (DBDs) in air, nitrogen and argon at atmospheric pressure. The plasma-modified surfaces were characterized by contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The polymer surface, modified by DBD at atmospheric pressure, showed a significant decrease in water contact angle although a partial recovery of the surface wettability occurred during the first few days after the treatment. However, the process of hydrophobic recovery was insufficient for complete recovering of the samples original wettability. XPS analysis showed an increase of the oxygen concentration on the surface, due to the formation of polar groups, such as C-O and OC= O. A small increase in the concentration of nitrogen was also observed. AFM images exhibit an increased roughness of the treated polymers because of the physical interaction between the species generated in the discharge and the polymer surface. The activated surface and high surface tension of treated polymers should promote an enhancement of the polymer adhesion to paints and coatings.
Orientador: Konstantin Georgiev Kostov
Coorientador: Roberto Yzumi Honda
Banca: Konstantin Georgiev Kostov
Banca: Rogério Pinto Mota
Banca: Gilberto Petraconi Filho
Mestre
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Eder-Goy, Dagmar [Verfasser], Baixiang [Akademischer Betreuer] Xu, and Dietmar [Akademischer Betreuer] Gross. "Numerical Studies on the Influence of Dissipative Effects on Electromechanical Properties of Dielectric Polymers / Dagmar Eder-Goy ; Baixiang Xu, Dietmar Gross." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://d-nb.info/1199006602/34.
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Eder-Goy, Dagmar [Verfasser], Bai-Xiang [Akademischer Betreuer] Xu, and Dietmar [Akademischer Betreuer] Gross. "Numerical Studies on the Influence of Dissipative Effects on Electromechanical Properties of Dielectric Polymers / Dagmar Eder-Goy ; Baixiang Xu, Dietmar Gross." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://d-nb.info/1199006602/34.
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