Etudes thermodynamiques et structurales du nanocomposite polyethylene contenant des nanotubes de carbone multiparois.

Abstract

The results obtained show that the coefficient of thermal expansion of the nanocomposite PE+X%CNT is changed between the radial direction and the longitudinal one, whatever the concentration of carbon nanotubes. According to the radial direction,  is higher than the coefficients in the whole of the of temperature domain. According to the longitudinal direction, the dilatometric behaviour of the nanocomposite changes completely. Pure polyethylene presents a thermal expansion coefficient very large in comparison to that of the three others. The four curves contain each one a dilatometric anomaly. Its intensity depends on the concentration. We notice that the thermal expansion coefficient as well as the intensity of the dilatometric anomaly of the nanocomposite EP+1%CNT is the weakest one in front of the three others whatever the direction of measurement. The curves of differential scanning calorimetry of the four samples have the same form and the shapes are practically confused. They contain each one a calorimetric anomaly appearing at 95°C. Thermogravimetric measurements of the two nanomaterials containing respectively 1 and 2.5% NTC give curves which overlap and have intensities appreciably the same ones. As for the sample containing 0.5% NTC, its TG is very intense in front of the two other nanocomposites and that of pure material on all the studied temperature range. The Raman spectroscopy, of the studied samples, reveal that the intensities of the various peaks present on the four curves strongly vary according to the concentration in nanotubes. The curves of the pure sample and the nanocomposite EP+0.5%CNT are superposable. As for the spectra of two other nanomatérials containers 1 and 2.5%CNT, they have the same form and are superposable. The two spectra contain the same number of anomalies and appear at the same frequencies. The Raman intensity of the nanomaterial PE2.5%CNT is lower than the three others. The spectra obtained by the infrared illustrate an important intensification due to the introduction of the carbon nanotubes into polyethylene. The shapes of the curves of the three nanocomposites, whatever the concentration in multiwalled carbon nanotubes, changed form and became more intense in comparison to that of pure polyethylene. That of nanomaterial PE+1%NTC have the greatest intensity. The use of several experimental techniques for the realization of this work made it possible to highlight and to confirm the positive role of the carbon nanotubes introduced into polyethylene. The results obtained in this thesis are of an unquestionable contribution in the field of sciences of materials. Dilatometry enabled us to show that the nanocomposite containing 1%NTC has a low thermal dilation coefficient according to the temperature. This behaviour makes it interesting in the industrial field. The mechanical tests confirmed that the injection of carbon multiparois nanotubes in polyethylene made increase the elastic range. The Raman spectroscopy showed that the increase in the concentration in carbon multiparois nanotubes in polyethylene high density PEHD makes decrease the quantity of defects, improves qualities of the nanocomposite, reinforces the C-C bonds and led to an ordered structure.