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Doctoral Thesis
DOI
10.11606/T.76.1999.tde-15042014-095801
Document
Author
Full name
Mauro Miguel Costa
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1999
Supervisor
Committee
Giacometti, José Alberto (President)
Alfaro, Renê Armando Moreno
Guimaães Neto, João Mariz
Hernandes, Antonio Carlos
Ticianelli, Edson Antonio
Title in Portuguese
Estudo dos sistemas poliméricos: poliestireno e poli(metacrilato de metila) dopado com o corante vermelho disperso 1
Keywords in Portuguese
Coeficiente piroelétrico
Descarga corona
Polarização elétrica
Abstract in Portuguese
Neste trabalho foi investigado o comportamento elétrico dos sistemas poliméricos preparados com o poliestireno, PS, e poli(metacri1ato de metila), PMMA, dopados com o corante vermelho disperso 1, DR1. O processo de polarização dos filmes poliméricos foi realizado usando o triodo de corona operando em duas configurações: i) carregamento com corrente de carga constante, ii) com tensão de grade constante. O processo de polarização por corona foi investigado variando-se os parâmetros do processo, tais como: corrente de carga, tempo, temperatura, campo elétrico de saturação e porcentagem de corante das amostras. As medidas da corrente elétrica no estado estacionário em função campo elétrico permitiram mostrar que o processo de condução elétrica nos dois sistemas obedecem o modelo de Poole-Frenkel. O valor da polarização elétrica induzida foi avaliada através de medidas do coeficiente piroelétrico, o qual é diretamente proporcional a polarização na amostra. No caso do PS(DR1) deu-se ênfase a investigação de medidas de corrente termo estimulada para avaliar a polarização elétrica induzida nas amostras por aplicação de uma ddp. Medidas da constante dielétrica complexa para os dois sistemas poliméricos foram realizadas em função da freqüência para diferentes temperaturas. Os resultados obtidos mostraram que a orientação e relaxação dos corantes nas amostras são associados ao movimento das cadeias poliméricas, i.e., relaxação do tipo α.
Title in English
Study of polymeric systems: polystyrene and poly(methil-methacrilate) containing disperse red 1 dye
Keywords in English
Corona discharge
Electric polarization
Piroelectric coeficient
Abstract in English
Some electrical properties of guest-host polymeric systems made with polystyrene, PS, and poly(methyl methacrylate), PMMA, and the disperse red 1 dye, DR1 were investigated. The poling process of films were performed with the corona triode set up operating in two modes: i) charging with constant current, ii) with a constant grid voltage. The influence of parameters such as the charging current, electric field at the s, time, temperature and the percentage of DR1 was investigated. Measurements of the steady state current versus the electric field allowed us to show that the electric conduction process in both polymeric systems follow the Poole-Frenkel model. The electric polarization induced in samples was evaluated measuring the piroelectric coefficient, which is directly proportional to the polarization value. For PS(DR1) samples thermally stimulated current measurements were performed to investigate the electric polarization obtained by application of a dc voltage. Measurements of the complex dielectric constant with the two polymeric systems as function of the frequency for different temperatures were performed. Results showed that orientation and relaxation of DR1 dye in samples are related to the chain movement, i.e., α relaxation process.
 
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MauroCostaD.pdf (3.90 Mbytes)
Publishing Date
2014-04-17
 
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