Effect of chemical modification on the flow behaviour of LDPE and its blends with linear LDPE

Abstract

The flow behaviour of LDPE and its blends with linear LDPE (LLDPE) chemically modified with DCP was studied as a function of blend composition and shear rate at a constant temperature using a capillary rheometer. The effect of chemical modification on the viscous and elastic properties of LDPE and two blend systems LDPE/LLDPE (80:20, 60:40) is reported. Chemical modification which is in essence a free radical process induces changes that increase melt viscosity and melt elasticity of LDPE and the two blend systems. Modification also enhances compatibility of the molten polymers. Incorporation of a small quantity of linear LDPE having a relatively narrow molecular weight distribution to the conventional LDPE having a long chain branched structure and broader molecular weight distribution lessens the shear thinning behaviour of the modified blends of the two component polymers. Melt elasticity at a constant shear stress and temperature was also investigated using die swell measurements and relating them to recoverable shear strain, normal stress and shear modulus.