The mechanical and the crystallization behavior of melt-mixed cocontinuous blends of polyamide6 (PA6) and acrylonitrile butadiene styrene were studied in presence of multiwall carbon nanotubes (MWNT). Young's modulus was observed to be significantly improved with increasing concentration of MWNT, while only moderate improvements were observed in the tensile strength. To overcome the van der Waals' forces between MWNT a unique modifier, sodium salt of 6 amino hexanoic acid (Na-AHA) was employed where it was envisaged that specific interactions between Na+ of the modifier and the delocalized "pi-electron" clouds of MWNT would lead to significant debundiling of the tubes. The mechanical properties of the blends with Na-AHA modified MWNT were found to be improved as compared to the blends with purified MWNT however, were found to be adversely affected above certain concentration of Na-AHA in the blends. Dynamic mechanical thermal analysis supported the plasticization effect induced by Na-AHA manifesting in decrease in the glass transition temperature of PA6 in the blends with Na-AHA modified MWNT. Differential scanning calorimetry results showed two crystallization exotherms for PA6 in the blends with both purified and Na-AHA modified MWNT. This unusual crystallization behavior of PA6 was addressed in context to confined crystallization of PA6 in the tube "network-like" structure. POLYM. ENG. SCI., 49:1533-1543, 2009. (C) 2009 Society of Plastics Engineers