Abstract
The application of on-line rheometry is considered with particular reference to polymer melts plasticized by physical blowing agents. Experimental investigations were performed on polystyrene containing 0-15 wt% of HCFC-142b or HFC-134a or 0-5 wt% of carbon dioxide at various temperatures and shear rates. It was shown that results could be used to indicate the solubility limit and related to the glass transition temperature.
Rheological modelling and data fits were compared indicating that a time/ temperature-composition (i.e. relative concentrations of polymers/blowing agent mixtures) superposition principle was valid. The model was extended to consider effects using a semi-crystalline polymer (polypropylene).
It was concluded that an on-line retum-to-stream process control rheometer could satisfactorily measure and monitor mixtures of polymers and physical blowing agents used in thermoplastic foam extrusion. Appropriate viscosity measurements could be directly linked to a number of critical variables.
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