Yeh Wang

Melt processing of polypropylene/clay nanocomposites modified with maleated polypropylene compatibilizers

Maleic anhydride-grafted polypropylene (PPgMA) and organically modified clay composites were 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 compatibilizers 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 low melting point and high melt index was compounded at low equilibrium temperature in order to maintain a certain level of torque. 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 and thermogravimetric analysis, respectively. Though PPgMA with lower molecular weight and higher MA content could lead to good clay dispersion in PP/clay composites, it caused the deterioration in both mechanical and thermal properties of PP/PPgMA/clay composites.

Melt intercalation and exfoliation of maleated polypropylene modified polypropylene nanocomposites

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.

Clay dispersion and physical properties of melt-blended PP/organoclay nanocomposites: effect of interfacial interaction

Melt blending of maleic anhydride-grafted polypropylene (PPgMA) and organically modified clay nanocomposites was first carried out in a plasticorder. The structure was investigated with x-ray diffraction (XRD) and transmission electron microscopy (TEM). The interfacial interaction between PB3150 compatibilizer and I30 clay surface was altered with the addition of different loadings of PB3150. It was found at the PB3150 compatiblizer gave rise to a high degree of clay dispersion beyond the PB3150/I30 weight ratio of 3. We then also modified polypropylene/organoclay nanocomposites with different loadings of PB3150 on a twin-screw extruder. When the PB3150 loading exceeded 15 wt%, extensive exfoliation of clay was observed. 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 tensile and impact tests and thermogravimeric analysis (TGA), respectively. Although high loading of PB3150 leads to better clay dispersion in the polypropylene nanocomposites, it causes deterioration in both mechanical and thermal properties of the hybrid systems.