Structure and processing parameter relationship for poyolefin homo- and copolymers
László Halász, Károly Belina, Olof Vorster, Ioan Tincul
Technikon Pretoria
Hungary
Keywords: polyolefin copolymers, rheology, free volume
A series of random ethylene, propylene/1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene copolymers,
ethylene and propylene homopolymers were prepared and investigated. The rheological properties (steady state and dynamic shear viscosity, creep compliance and plateau modulus of copolymers with different comonomer content and with the almost same molecular masses were determined and compared with the properties of homopolymers. The effects of the length of co-unit and the comonomer content were investigated. The copolymers exhibited similar rheological properties to the homopolymer but they have a lower shear viscosity, normal viscosity , higher steady state crrep compliance and smaller plateau modulus values. The increase of length of co-unit causes a decrease in the zero shear viscosity in the case of the same molecular mass and comonomer content.. The effect of comonomer contant was evaluated on the basis of free volume theory.