Phase Diagrams of Blends of Poly(phenylene ether) (PPE), Polystyrene (PS) and Diglycidyl Ether of Bisphenol A (DGEBA): Influence of the Molar Mass of PPE

E.R. SOULÉ; T. FINE; J. BORRAJO; R.J.J.WILLIAMS; J.P.PASCAULT

JOURNAL OF APPLIED POLYMER SCIENCE

JOHN WILEY & SONS INC

Año: 2006 vol. 100 p. 1742 - 1747

0021-8995

Blends of poly(2,6-dimethyl-1,4-phenylene oxide), usually called poly(phenylene ether) (PPE), and polystyrene (PS) in a reactive solvent based on diglycidyl ether of bisphenol A (DGEBA), are used to facilitate processing of PPE. The process starts with an initial homogeneous solution and the final material is obtained by polymerization-induced phase separation. In this study, experimental phase diagrams of these ternary blends were obtained in an extended range of temperatures for two commercial PPEs of different molar masses (Mn = 1.2 kg mol-1 and 12 kg mol-1). Overall experimental trends including the appearance of an immiscibility loop for the PPE(1.2 kg mol-1)-PS-DGEBA blend, were reasonably predicted using the Flory-Huggins (FH) model with interaction parameters obtained from the literature (for PPE-PS blends) or by fitting experimental cloud-point curves of the corresponding binary systems (for PPE-DGEBA and PS-DGEBA blends). The FH model was then used to predict the influence of the PPE molar mass on the miscibility of ternary blends. A significant increase in miscibility together with the appearance of an immiscibility loop was found for PPEs with Mn values comprised in the range between 1 and 10 kg mol-1. Using a PPE of low molar mass opens the possibility of obtaining initial homogeneous solutions with a high fraction of the epoxy precursors. Polymerization-induced phase separation starting from these solutions can lead to a dispersion of thermoplastic domains in an epoxy matrix or to bi-continuous phases. What is significant is the fact that properties of the thermoplastic phase can be modulated by varying the ratio of both thermoplastics and the molar mass of PS. This opens new possibilities for the toughening of epoxies replacing a single thermoplastic with a thermoplastic blend.