Compatibilized polyimide (R-BAPS)/BAPS-modified clay nanocomposites with improved dispersion and properties

There is a need for clay modifiers that will not thermally degrade at elevated temperatures commonly used in polymer processing operations such as extrusion and injection molding. In this context, natural montmorillonite clay (Na-MMT) was organically modified by varying concentrations of 4,4′-bis(4″-aminophenoxy)diphenylsulfone (BAPS) using different chemical dispersion methods to yield new chemically modified clays that are relatively thermally stable at elevated temperatures compared with current commercial modified clays. This paper shows that the Na-MMT chemical modification (BAPS-MMT) was confirmed by XRD that showed a shift of diffraction peak at 2Θ = 7.3° for Na-MMT towards lower 2Θ = 5.8°. Thermogravimetric analysis of the samples showed a weight loss of organically modified clay that started at a temperature of 350 °C, corresponding to the degradation temperature of the BAPS monomer. Rheological measurements in combination with XRD data showed clearly that the quality of dispersion of BAPS-MMT type particles in R-BAPS type polyimide and oligoimides strongly depends on the clay surface modification, the specific chemical modification method used, and on the polymer molecular weight. Note that the oligoimides were specifically used as model systems to confirm our expectation of improved chemical compatibility between the BAPS-MMT and the polyimide system. This study may stimulate a better understanding of the effects of rational chemical modification methods on the quality of clay dispersion in polyimide matrices, enhancing our ability to prepare useful polyimide/clay nanocomposites with improved properties for targeted high-temperature applications where current polymer nanocomposite systems are not useable.