Thermal degradation of polyesters filled with magnesium dihydroxide and magnesium oxide
SUMMARY Magnesium dihydroxide (MDH) was evaluated as char promoter into different polymers exhibiting various chemical structures. Char promotion was characterized using thermogravimetric analysis and pyrolysis combustion flow calorimetry. Gases released during pyrolysis were identified using pyrolysis coupled gas chromatography/mass spectrometry and thermogravimetric analysis coupled Fourier transform infrared spectroscopy. Relationships between the MDH effect (according to the char content and its thermal stability) and the chemical structure of the host polymers were identified. It was shown that MDH can be a good char promoter for aromatic polyesters such as polybutylene terephtalate and polyethylene terephtalate. Char promotion can be considered as one of the main mode of action of MDH at low or moderate filler content. An optimum was observed at approximately 20wt. of MDH. Magnesium oxide was also studied as substitute to MDH to avoid hydrolysis phenomena due to the water release. But it was demonstrated that MDH was more efficient as a char promoter for polybutylene terephtalate than magnesium oxide. Copyright (c) 2015 John Wiley Sons, Ltd.