THERMAL STABILITY AND THERMOMECHANICAL PROPERTIES OF EPOXY COMPOSITES REINFORCED WITH CARBON NANOTUBES

The thermal stability and thermomechanical properties of an epoxy composite based on ED-20 epoxy oligomer cured with a polyaniline complex doped with tetrafluoroboric acid (PAn-BF3) The thermal stability and thermomechanical properties of an epoxy composite made from the ED-20 epoxy oligomer, cured with a polyaniline complex doped with tetrafluoroboric acid (PAn-BF3), were examined using differential thermogravimetry (DTG) and thermomechanical analysis (TMA).were investigated using differential thermogravimetry (DTG) and thermomechanical analysis (TMA). Multi-walled carbon nanotubes (MWCNTs) with unmodified (MWNT) and phenyl diazonium tetrafluoroborate-modified surfaces (mMWNT) were used as fillers. At the final stages of thermal degradation at T > 600 °C, the nature of the thermogravimetric curves and the conversion characteristics of polymer thermal degradation are virtually independent of the nature and mass of carbon nanotubes in the composite. At the initial stages of the process, including the region of rapid degradation, the conversion and temperature characteristics of thermal degradation indicate the influence of the nature of carbon nanotubes on the process. While in the case of pristine (unmodified) MWCNTs, the temperature of the onset of polymer mass loss Tp is practically independent of the MWCNT content, in the case of modified mMWNTs, mass loss of the composite is observed at significantly lower temperatures. An increase in the mMWNT content to 2.5 wt% causes a further decrease in the temperature Tp. The reduction in the thermal stability of epoxy composites filled with mMWNTs is chemical. It is associated with the thermal desorption of the modifier - phenyl diazonium tetrafluoroborate from the surface of MWCNTs. The results of the thermomechanical analysis of the studied epoxy polymer composites show that the introduction of a nanoscale filler leads to a significant improvement in the thermomechanical stability of the polymer matrix. This is shown by an increase in the glass transition temperature (Tg), the temperature of the polymer transition to a highly elastic state (Thes), and the high elasticity modulus. This effect is most significant for composites containing 2.5 wt.% carbon nanotubes.