Morphology development was investigated during blending of linear low density polyethylene (LLDPE) and polystyrene (PS) (the minor phase) in a tangential counter-rotating twin screw extruder, with and without the use of 5 wt.-% Kraton styrene-ethylene/butylene-styrene (SEBS) triblock copolymers as compatibilizing agents. Dispersive mixing in the Non-Intermeshing Twin Screw Extruder (NITSE) is improved with an increase of percent drag flow up to 50 %; the screws configuration includes reverse flight elements and/or cylinders. Experiments have indicated that the combined effect of the reverse flight elements and cylinders increases the reduction rate of droplets due to a longer time in the feed screw where the most significant changes of phase morphology occur. Screw stagger has been shown to have a minor effect on the phase scale of the final dispersion. The more significant reduction of the phase scale is achieved by increasing screw speed under constant flow conditions.
© 1997, Carl Hanser Verlag, Munich