The sericite mica was first treated by heating and acid dipping followed by LiNO3 treatment.The organophilic clay was subsequently achieved by inorganic-organic ion exchange in the hydrothermal reaction of LiNO3-treated sericite mica with intercalating agent-hexadecyltrimethylammonium bromide solution.Finally

a series of polyimide (PI)/sericite mica composites were prepared via in situ polymerization reaction.The effects of the reaction temperature and the amount of intercalating agent added on the modification of sericite mica were investigated.The structures of modified and original sericite mica were systemically characterized with X-ray diffraction (XRD)

Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM)

showing the best intercalating effect was observed when the reaction temperature was 180 ℃ and the amount of intercalating agent added was fifteenfold the cation exchange capacity (CEC).Under the above reaction conditions

the d002 basal spacing of the sericite mica was increased from 0.99 nm to 2.77 nm.The structure of the composites was investigated by XRD and high resolution transmission electron microscopy (HRTEM)

and the thermal stability and the mechanical properties were studied by means of thermogravimetric analysis (TGA) and mechanical property measurements

indicating that the PI/original sericite mica composite was a simple physical blend of PI and pure sericite mica

while the PI/organic sericite mica nanocomposites was an exfoliated structure with 5 wt% loading

and the nanocomposites with the content of 1 wt%~7 wt% organophilic sericite mica exhibited no observable peaks in the range of 0.5~10 (2)

which revealed that majority of the d002-spacing of organophilic sericite mica had been intercalated to a distance of more than 4.42 nm (21).When the mass ratio of sericite mica and PI was 5:100

the tensile strength

Young's modulus and elongation at break of the PI/organic sericite mica nanocomposites are 1.79

1.40 and 1.83 times those of the PI/original sericite mica counterpart

respectively.The thermogravimetric analysis showed that the thermal stability was tremendously enhanced with the increasing organophilic sericite mica content and the nanocomposites with 7 wt% loading revealed a 36 K increment in T5 (the temperature at 5 wt% weight loss) compared with pristine PI.