Separation of thermoplastic polymer blends with high-pressure, high-temperature subcritical heptane (7 pag)

M. DIAZ; G. MABE; S. BARBOSA; N. CAPIATI

Foz de Iguazú, Brasil

Conferencia; VI Conferencia Iberoamericana sobre Equilibrio entre Fases para el Diseño de Procesos. EQUIFASE 2002; 2002

The separation of thermoplastic polymer blends into their  components is a well-known method to analyze the blend composition and morphology. Usually it is done by selective solvent extraction in a Soxhlet apparatus. However when the blend components are high molecular weight polymers the total separation is very difficult, because of the solubilization of large molecules. The problem is harder when the blend contains compatibilizers (generally its copolymers) because it is necessary to separate the blend components and the copolymer. The use of a high temperature - high pressure subcritical solvent is an interesting alternative to obtain a complete and speedy blend separation. In this work, a polymer blend components separation, using subcritical n-heptane, is proposed. The system analyzed was PE/PS/n-heptane, using commercial high molecular weights polymers. The solvent selectivity was experimentally studied on a wide range of temperatures to obtain the processing windows for the blend separation. Also the influence of the blend morphology and composition on the efficiency of the polymer separation was studied. It was demonstrated that the separation of the blend is complete (the entire PE phase can be extracted by the n-heptane in one hour) when the PE is the majority phase in the blend. The method proposed for blend separation is easy, rapid and accurate for this system. Keywords: Thermoplastic blends separation, SCF polymer extraction, blend extraction