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Master's Dissertation
DOI
https://doi.org/10.11606/D.54.1983.tde-09122013-113235
Document
Author
Full name
Hermes Adolfo de Aquino
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1983
Supervisor
Committee
Ferreira, Guilherme Fontes Leal (President)
Gross, Bernhard
Gupta, Hari Mohan
Title in Portuguese
Experiências de polarização e condução nos polímeros PVDF e FEP
Keywords in Portuguese
Condução e polarização
Polímeros PVDF e FEP
Abstract in Portuguese
Nesta dissertação relatamos os resultados de medidas elétricas realizadas, a maioria delas, em folhas de 25μm de polivinilidene de flúor (PVDF), e em menor número em folhas de tetrafluoretileno-hexafluorpropileno (Teflon FEP). Correntes de polarização sob variadas tensões e de despolarização foram medidas a várias temperaturas e com temperatura variável. O PVDF sofre modificações, possivelmente estruturais, sob aquecimento acima de 100°C quando um campo elétrico parece produzir uma limpeza elétrica, resultando uma condutividade menor. As polarizações são do tipo t-n, indicando, no caso do PVDF uma distribuição em freqüências e para o FEP tratado termicamente a 200°C, uma em energia. Apesar das amostras de PVDF fornecerem resultados pouco reprodutíveis, pode-se concluir que para os campos empregados o comportamento é razoavelmente linear na polarização e superlinear para a condutividade. Observou-se também um comportamento anômalo da corrente, no PVDF, sob a ação prolongada de campo aplicado, mesmo para as menores tensões. Para o FEP o comportamento da corrente para os diversos campos usados foi bastante irregular embora as polarizações e as subseqüentes despolarizações coincidissem na maioria dos casos
Title in English
Experiments on conduction and polarization in PVDF and FEP polymers
Keywords in English
Conduction and polarization
PVDF and FEP polymers
Abstract in English
We present here the results of electrical measurements performed, most of them, in 25μm foils of polyvinylidene fluoride (PVDF), and fewer in flois of tetrafluorethilene-hexafluorpropilene (Teflon FEP). Polarization currents under varied applied voltages and the corresponding depolarizations were measured at constante temperature and during heating and cooling. The PVDF exhibits modifications, possibly its structure changes, if heated above 100°C; in this case an electric field seems to clean the sample since its conductivity strongly decreases thereafter. The polarizations are of the t-n type, poiting to a distribution of frequencies inPVDF and of energies in FEP previously annealed at 200&#C. Although the results are poorly reproducible, some conclusions could be drawn for the PVDF: the polarization is nearly linear with the field but the conductivity shows a super linear dependence. An anomalous behavior of the current was observed at long time under tension, even the smallest use here. In the case of FEP, the magnitude of the current in relation with the voltage hás shown an irregular behavior, although polarization and the corresponding depolarization do indeed coincide in most cases
 
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Publishing Date
2013-12-10
 
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