Crystallization and Rheological Behaviors of Amino-functionalized Multiwalled Carbon Nanotubes Filled Polyamide 6 Composites

Multiwalled carbon nanotubes/polyamide 6 (MWNTs/PA6) composites were fabricated by melt blending with both pristine MWNTs (p-MWNTs) and amino-functionalized MWNTs (f-MWNTs). The crystallization and rheological behavior of MWNTs/PA6 composites were investigated. The results showed that all the MWNTs can act as heterogeneous nucleation sites; however, they retard the growth process. It was found that the apparent viscosity of the composites was lower than PA6 at lower p-MWNT content, but was higher than PA6 at higher p-MWNT content. This was attributed to the stiffening effect of MWNTs and the broken physical crosslinks between PA6 chains caused by a large amount of MWNTs. The storage modulus of the f-MWNTs/PA6 composites was first increased and then decreased with the increase of f-MWNT content because of the crystallization and the stiffening effect of f-MWNTs. However the glass transition temperatures (Tg ), characterized by the tan δ peak, for all composites were lower than that of neat PA6. Amino-functionalization of MWNTs improved the interaction between MWNTs and PA6, and weakened the effect of MWNTs on crystallization and rheological behavior.