Nanocomposites of low density polyethylene (LDPE) and C18 modified multi wall carbon nanotubes (C18-CNT) were prepared by melt blending. Previous research has shown that addition of carbon nanotubes (CNTs) increase the dynamic viscosity and reduce the extensional viscosity with increasing loading. This research work shows that C-18 modification of CNTs helps to keep low values of dynamic viscosity, maintain extensional viscosity and does not increase strain hardening even at 5.0 weight % loading.