A COMPARATIVE-STUDY ON THE PERFORMANCE OF 3 SINGLE-SCREW ELEMENTS IN MELT-MELT MIXING IMMISCIBLE BLENDS

An experimental investigation was conducted to evaluate the performanc e of three single-screw mixing elements: a Maddock; a Pineapple; and a Twente mixer. The study was designed to focus on the mixers' performa nce in the mixing of immiscible polymers in the molten state. Two inde pendently controlled melt streams were fed to the mixer and the evalua tion of the mixer performance was based on the following criteria: (i) the processing characteristics, namely the pressure drop/rise across the mixer for specific machine and material operating variables; and ( ii) the resulting quality of mixing as determined by image analysis of phase morphology on samples collected at the die. The mixing performa nce was judged both qualitatively, in terms of spatial material distri bution, as well as quantitatively, by analysis for the size of the dis persed phase. The blending tests were conducted using three pairs of L DPE/PS systems having different rheological properties. In addition to the experimental work, the flow in the Maddock mixer was simulated us ing a commercial finite element package (FIDAP). The calculations were done using the experimental conditions and the properties of a pure L DPE phase. The simulation results were used to explain the dispersion data obtained experimentally. (C) 1998 John Wiley & Sons, Inc.