Flame retardancy of bio-based polyether-block-amide polymer (PEBAX)

Abstract

Bio-based polymers are becoming an important class of polymers. This paper deals with the enhancement of flame retardancy properties for the bio-based polymer Pebax, a polyether-block-amide copolymer. Fire retardancy of Pebax with melamine combined with an organomodified montmorillonite clay (cloisite) as fire retardant additives is evaluated by cone calorimetry and limiting oxygen index (LOI). It is found that the best fire retardant properties are observed for a material containing 70 wt% Pebax, 26 wt% melamine and 4 wt% cloisite. To get a better understanding of the role of cloisite, the mechanism of action is investigated for this material compared to a material containing 70 wt% Pebax and 30 wt% melamine. The dispersion of the additives is first examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is found that all additives are well dispersed in the matrix. Further the thermal degradation, the condensed and the gas phase mechanism of both materials were investigated using thermogravimetric analysis (TGA), solid state nuclear magnetic resonance (NMR) of 13C and of 27Al and thermogravimetric analysis coupled with a Fourier transform infrared spectrometer (TGA–FTIR).It is shown that the material containing only melamine is protected through a gas phase mechanism. Thereby melamine and its degradation products protect the material through a gas phase mechanism. The replacement of 4 wt% melamine by cloisite results an additional protection of the material via condensed phase mechanism. A char layer, that acts as a physical barrier is formed during combustion. Concurrently, melamine and its degradation products act in the gas phase.