Aplicação da calorimetria diferencial da varredura modulada no estudo de blendas polimericas

AUTOR(ES)
DATA DE PUBLICAÇÃO

2001

RESUMO

Temperature modulation was implemented in the differential scanning calorimetry (DSC) in the 1990 s, allowing separation of thermodynamic and kinetic phenomena. In this case, a mathematical treatment of data is necessary. The purpose of this work is to evaluate the application of modulated DSC on the study of polymeric blends made of poli(vinyl alcohol) and poli (vinyl pyrrolidone) at several compositions, varying the degree of hydrolysis of the first polymer and the molar weight of the second. The instrumental parameters, heating rate, modulation amplitude and modulation period, were optimized. Lissajous figures were used to evaluate stability in the temperature modulation and the blend viscoelastic properties during phase transitions. It was possible to identify the glass transitions in all the composition range due to the optimization of the instrumental parameters. High modulation amplitudes associated with high heating rates allowed better sensibility for the detection of glass transitions. It was observed that the blends glass transition and melting are modulation amplitude dependent processes. As the modulation period increases, the glass transition temperature decreases and the fusion enthalpy increases. It was possible to observe modifications in the inclination of the Lissajous ellipses during glass transition. It was attributed to the variation in the material heat capacity during transition.

ASSUNTO(S)

calorimetria reações em cadeia de polimerase

ACESSO AO ARTIGO

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