Abstract: A composite foaming agent composed of montmorillonite (MMT) and azodicarbonamide (AC) was prepared by intercalating AC into MMT in supercritical CO2 medium, and then was characterized by Fourier-transform infrared spectroscopy, thermogravimetric analysis, powder X-ray diffraction and scanning electron microscopy. An optimum condition of 40 ℃, 20 MPa and 100 r/min for the supercritical intercalation was obtained on the basis of the investigation of intercalating effect and morphology of the ACintercalated MMT. The agglomeration structure of MMT was improved at this condition. The MMT/AC composite foaming agent could be directly used for the foaming process of polypropylene (PP) without any other additives. PP foams achieved a cell size of about 250 μm and a uniform size distribution at an injection molding temperature of 190 ℃.

Key words: supercritical carbon dioxide, azodicarbonamide, montmorillonite, composite foamingagent