Comparative performance of carbon nanotubes and nanoclays as flame retardants for epoxy composites

摘要

The pyrolysis characteristics of a nanoparticle-reinforced epoxy matrix composite were investigated to gain a better understanding of the basic mechanisms for flame retardancy. A two-dimensional transient-state model was developed to provide a better understanding of the pyrolysis process of the composite subjected to incident radiation. The dependence of composite flame retardant properties on the type of nanoparticle reinforcements were studied. The effectiveness of carbon nanotubes and montmorillonite nanoclays in reducing the flammability of polymeric resin was discussed. The rate of mass loss was used as an indicator for evaluation of the effectiveness of flame retardants associated with the pyrolysis process of the composite. This study specifically focuses on how the thermal properties of a continuous network-structured protective layer formed by flame retardants influence the flammability of an epoxy matrix composite containing less than 0.8% by weight of carbon nanotubes or less than 8.0% by weight of montmorillonite nanoclays. The results indicated that the reduction in composite flammability results primarily from the network-structured layer formed by flame retardants between the unburned and burning parts of the polymer. The thermal properties of the network-structured layer are of great significance to improve the effectiveness of flame retardants in reducing the flammability of the composite. Carbon nanotubes are more effective than nanoclays in reducing the flammability of the composite, even with up to a ten-fold difference in the loading of flame retardants. Both flame retardants can lead to a more than 60% reduction in the rate of mass loss in the pyrolysis process. Unfortunately, carbon nanotubes suffer the disadvantage of a much higher rate of mass loss at the initial stage of the pyrolysis process due to the enhanced heat-transfer ability of the network-structured layer. Implications of the results on flame retardancy mechanisms in polymer matrix composites were also discussed.