Grafting of polyethylenes by reactive extrusion. II. Influence on rheological and thermal properties

In this article, the effects of the grafting degree and the processing cond itions employed to prepare LLDPEs-g-DEM and HDPEs-g-DEM via reactive extrus ion on their rheological and thermal properties were studied. The rheologic al properties of the virgin samples of LLDPEs, HDPEs, and their functionali zed products were determined using capillary and dynamic rheometry. The the rmal behavior of the virgin materials and their grafted products was examin ed by differential scanning calorimetry (DSC). It was found that the rheolo gical properties are more sensitive than are the molecular structure charac teristics to the changes produced by the grafting reactions with DEM, under the employed experimental conditions. There is an increase in the dynamic viscosity at low frequencies, in the storage modulus, and in the shear-thin ning behavior when the grafting degree increases. The crossover between G " and G' moves to lower frequencies and the relaxation time spectrum functio ns are broader in the grafted materials. (C) 1999 John Wiley & Sons, Inc.