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Viscosity ratio effects in the compounding of low viscosity, immiscible fluids into polymeric matrices
Author(s) -
Scott Chris E.,
Joung Sandra K.
Publication year - 1996
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.10563
Subject(s) - compounding , materials science , polystyrene , polyethylene , viscosity , reduced viscosity , mixing (physics) , polymer , phase inversion , thermodynamics , softening point , composite material , polymer chemistry , chemical engineering , chemistry , biochemistry , physics , quantum mechanics , membrane , engineering
Abstract Many low viscosity, immiscible fluids are difficult to incorporate into polymer matrices because of thermodynamic immiscibility and a large mismatch of melt viscosities. In this investigation, a model system was used to determine the mechanisms and kinetics of mixing in such formulations. The model systems consisted of a series of different molecular weight polyethylenes in polystyrene. The viscosity ratio, η(polyethylene)/η(polystyrene), at 180°C and 100 s −1 was varied from 0.7 to 0.003. Phase inversion was observed during the compounding of these formulations. The phase inversion was associated with a transition from low to high mixing torque during compounding. This change was primarily due to an increase in the blend viscosity caused by the morphological transformation. The melting behavior during compounding depended on the melt viscosity of the polyethylene. A critical viscosity ratio of ≈ 0.1 exists below which softening of the polystyrene, and thus mixing of the two components, was greatly retarded. Even at very low concentrations, low viscosity polyethylene can have a significant effect on the processing behavior. Effects of mixer set temperature, degree of fill, and polyethylene particle size were explored. The roles of thermal conduction and mechanical energy input were evaluated in the melting regime of the process.