Preparation of poly(methyl methacrylate)/clay nanocomposites using supercritical fluid process

Organoclay-based poly(methyl methacrylate) (PMMA) nanocomposites were prepared using a chlorodifluoromethane (HCFC-22) solvent by the supercritical fluid process. Mechanical properties, transmission electron microscopy (TEM), wide angle X-ray diffraction (WAXD), and thermal stability were characterized for PMMA nanocomposites. Commercially available organoclays (ASM clay) treated with alkyl ammonium salt, such as Cloisite^® 15A and Cloisite ^® 30B, were compared with lab-made organoclays (FSM clay); specifically, sodium montmorillonite modified with a fluorinated surfactant. Ultrasonic treatment in the preparation of FSM clay was also investigated. Since the fluorinated tail in FSM clay is compatible with HCFC-22, FSM clay processed with ultrasonication showed partial exfoliation for PMMA/FSM clay nanocomposite, resulting in better thermal and mechanical properties and higher glass transition temperature as opposed to the intercalation morphologies for PMMA/ASM clay.