RHEOLOGICAL BEHAVIOR OF CONCENTRATED-SOLUTIONS OF ACRYLIC COPOLYMERS IN ETHYLENE CARBONATE

Solutions of acrylonitrile/vinyl acetate/alpha-methyl styrene copolymers in ethylene carbonate evidence pseudoplastic behaviour, characterized by viscosity decrease as a function of shear rate. The newtonian range of the flow curves corresponds with the Ostwald-de Waele model, and the extent of this domain depends on the type of polymer. For polymers with high content of endgroups and lower polydispersity the newtonian domain is more extended. The values of shear modulus G decrease with higher content of endgroups in the polymer. Relaxation times change in the same direction, which leads to increase of solution elasticity and results in possibilities of increasing spinning velocities. The apparent activation energy of viscous flow is lower for less polydispersed copolymers.