A physical and mechanical characterization of blends of Nylon 6 (PA6) and very low density polyethylene (VLDPE), functionalized with maleic anhydride (MA) or diethylmaleate (DEM) is reported. The functionalization of VLDPE with MA and DEM was performed by reactive extrusion in a twin-screw (Berstoff) extruder in the presence of dicumylperoxide. The PA6/VLDPE, PA6/VLDPE-g-MA, and PA6/VLDPE-g-DEM blends with composition ratio of 80 : 20 (wt %) were obtained by using a twin-screw Werner & Pfleiderer extruder. An industrial-type blend based on PA6 and MA-grafted ultra low density polyethylene (ULDPE-g-MA) was also tested for comparison. All blends were then characterized by optical and scanning electron microscopy, differential scanning calorimetry, and dynamic mechanical thermal analysis. The results of slow fracture and impact tests showed that the ductile-brittle transition temperature of the examined blends depends on the type of functional group and test speed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3455–3468, 1999