Multiwalled carbon nanotubes (MWNT) were functionalized with amine groups using a 'grafting to' technique. The oxidized MWNT (MWNT-COOH) were converted to the acyl chloride functionalized MWNT (MWNT-COCI) by treating them with thionyl chloride (SOCl2) and then MWNT-COCI was reacted with hexamethylenediamine to prepare MWNT-NH2. The formation of MWNT-NH2 was confirmed through the FTIR observation. MWNT-NH2/nylon 6 composites with different MWNT loadings were prepared by the simple melt compounding approach. A fine dispersion of MWNTs throughout nylon 6 matrix was observed by SEM and TEM. The fractured surface of the composites showed not only a uniform dispersion of MWNTs but also a strong interfacial adhesion with the matrix, as evidenced by the presence of many broken but strongly embedded MWNTs in the matrix in the absence of debonding of MWNTs from the matrix. Incorporation of MWNTs improved the mechanical properties significantly. Higher thermal stability was obtained for the composites with better dispersed MWNTs. (c) 2006 Elsevier Ltd. All rights reserved.