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Doctoral Thesis
DOI
10.11606/T.88.2000.tde-22082015-112346
Document
Author
Full name
Romildo Jeronimo Ramos
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2000
Supervisor
Committee
Faria, Roberto Mendonça (President)
Andrade, Adnei Melges de
Dirani, Ely Antonio Tadeu
Marega Junior, Euclydes
Motheo, Artur de Jesus
Title in Portuguese
Propriedades elétricas de polietileno impregnado com negro de fumo
Keywords in Portuguese
Condutividade elétrica
Negro de fumo
Polietileno de baixa densidade
Ruptura dielétrica
Abstract in Portuguese
Esta tese trata-se dos estudos dos mecanismos relacionados com a condução elétrica ac de polietileno de baixa densidade (PEBD), virgem e envelhecido sob radiação UV, carregado com diferentes concentrações de negro de fumo (NF). Medidas experimentais de condutividade ac foram feitas em amostras com diferentes concentrações de NF, em diferentes temperaturas. Análise de calorimetria diferencial (DSC) e medidas de expansão térmica foram realizadas como complementos a esse estudo. Observamos também o efeito do envelhecimento UV sobre as propriedades elétrica das amostras. Baseado na distribuição do NF na matriz polietileno, a condutividade ac foi explicada em termos do mecanismo "hopping" considerando o material como um sistema onde as barreiras de energia potencial estão aleatoriamente distribuídas no volume do material. Estudamos a ruptura dielétrica do PEBD/NF com diferentes concentrações de NF, e os resultados foram interpretados usando a distribuição estatística de Weibull, utilizando tanto o métodos gráfico quanto o analítico, para determinar a rigidez dielétrica e os parâmetros de escala e de forma da distribuição
Title in English
Not available
Keywords in English
Not available
Abstract in English
We performed a study of mechanisms related to ac electrical conduction of virgin and aged low-density polyethylene (LDPE) charged with different concentrations of carbon black (CB). Experimental ac conductivity measurements were carried out in samples of different CB concentrations for several temperatures. Measurements of differential scanning calorimetry (DSC) and of thermal expansion were performed as auxiliary methods in this study. We also observed the ultraviolet aging effect on the electrical properties of the samples. Based on the distribution of the CB in the polyethylene matrix, the ac conductivity was explained in t e m of hopping mechanism considering the material as a system where the energy potential barriers are randomly distributed in material bulk. We also performed studies of dielectric breakdown of LDPE/NF with different CB concentrations, and the results are studied by Weibull approach, using both analytical and graphic methods to determine the dielectric strength and the scale and shape parameters
 
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Publishing Date
2015-08-24
 
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