Influência da variação do tempo e da temperatura na cura de tintas: tinta pó epóxi e tinta líquida acrílico-epóxi. análise da dureza e da energia de conversão

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

The objective of this dissertation is to present a study of the influence of the time and temperature variation on the cure of thermosets paints. Two distinct systems were studied: acrylic-epoxy liquid paint and epoxy powder paint. The specimens were made out of metallic sheet. Afterwards, they were pretreated and soon after that they were painted by using appropriate equipments. The cure of the specimens was done in a steady oven. The variation of temperature of the cure process was registered through a thermograph, making it possible to follow the oscillations of the air and the metallic sheet temperatures throughout the experiments. The study of the specimens was done through the cured paint thickness and the measurement of the superficial hardness, by Knoop micro-indentation, and also through thermal analysis Differential Scanning Calorimetry (DSC). The acrylicepoxy paint presented and increase in hardness due to the increase of the time and the temperature cure. The results of the thermal analysis of the liquid paint indicate a gradual release of energy during the cure, exothermal process, resulting from the chemical reaction of the material crosslink. Through the energy values it was possible to calculate the degree of conversion and the conversion rate, and the relation between them, as well as their representation according to the time variation. It was possible to describe analytically the behavior of the material through the two techniques of characterization, correlating the degree of cure with the degree of conversion of the liquid paint and determining a correlation between them. For the epoxy powder paint, besides the cure energy, it was also evaluated the variation of the glass transition temperature (Tg) as function of the cure time. The increase of the Tg as function of the increase of the cure time, at the same temperature, indicates that the bigger the material crosslink, the bigger the energy necessary for the movement of its molecules. It was feasible to correlate the Glass Transition Temperature with the degree of conversion of the powder paint and find a correlative coefficient. The results obtained for the two systems made it possible to describe the cure reaction kinetics of the thermoset paints, without detailing the chemical reactions involved in the cure process of the materials.

ASSUNTO(S)

engenharia de materiais e metalurgica tintas calorimetria

ACESSO AO ARTIGO

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