Melt intercalation and exfoliation of maleated polypropylene modified polypropylene nanocomposites

Abstract

Melt blending of maleic anhydride-grafted polypropylene (PPgMA) and organically modified clay nanocomposites were first prepared in a plasticorder. PPgMAs, including PB3150, PB3200, PB3000, and E43, with a wide range of MA content and molecular weight were used. The structure was investigated with X-Ray diffraction (XRD) and transmission electron microscopy (TEM). PPgMA compatiblizers gave rise to similar degree of dispersion beyond the weight ratio of 3 to 1 with the exception of E43, which had the highest MA content and the lowest molecular weight. It was found that thermal instability and high melt index were responsible for ineffective modification by E43. Furthermore, PPgMA with lower molecular weight and higher melt index had to be compounded at lower mixing temperature in order to achieve a reasonable level of torque for clay dispersion. We then modified polypropylene/organoclay nanocomposites with different levels of PPgMA compatibilizers on a twin-screw extruder. The PP/E43/clay system, as shown through XRD patterns and TEM observation, yielded the poorest clay dispersion among the compatibilizers under investigation. The relative complex viscosity curves also revealed a systematic trend with the extent of exfoliation and showed promise for quantifying the hybrid structure of the nanocomposites. Mechanical properties and thermal stability were determined by dynamical mechanical analysis (DMA) and thermogravimeric analysis (TGA), respectively. Though PPgMA with lower molecular weight would lead to better clay dispersion in the polypropylene nanocomposites, it caused deterioration in both mechanical and thermal properties of the hybrid systems.