Thermoplastic Blends Demixing by High Pressure High Temperature Process

BARBOSA, SILVIA ELENA; DÍAZ, MÓNICA FÁTIMA; MABE, GUILLERMO; BRIGNOLE, ESTEBAN ALBERTO; CAPIATI, NUMA JOSÉ

JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS

Wiley

Año: 2005 vol. 43 p. 2361 - 2369

0887-6266

The analysis of thermoplastic polymer blends requires a precise separation of the blend components, which is usually performed by selective solvent extraction. However, when the components are high molecular weight polymers, a complete separation is very difficult. The use of fluids in near and supercritical conditions, becomes a promising alternative to reach a much more precise separation. In this work, a method to separate reactive and physical blends from high molecular weight commercial polymers is proposed. PE/PS blends were separated into their components by using propane, n-pentane and n-heptane at near and supercritical conditions. The selectivity of each solvent was experimentally studied over a wide range of temperatures for assessing the processing windows for pure components separation. The entire PE phase is solubilized by pentane and n-heptane at similar temperatures, while propane at supercritical conditions cannot dissolve the fraction of high molecular weight PE. The influence of the blend morphology and composition on the efficiency of the polymer separation was studied. In reactive blends, the in-situ copolymer formed was solubilized with PE phase by chemical affinity. The method proposed for blend separation is easy, rapid and selective and seems a promising tool for blend separation, particularly for reactive ones, where the isolation of the copolymer is essential for its characterization