Miscibility, melting, and crystallization of poly(butylene-2,6-naphthalate)/poly(ether imide) blends

We prepared blends of poly(butylene-2,6-naphthalate) (PBN) and poly(ether imide) (PEI) by solution-casting from dichloroacetic acid solutions. The miscibility, crystallization, and melting behavior of the blends were investigated with differential scanning calorimetry (DSC) and dynamic mechanical analysis. PBN was miscible with PEI over the entire range of compositions, as shown by the existence of single composition-dependent glass-transition temperatures. In addition, a negative polymer-polymer interaction parameter was calculated, with the Nishi-Wang equation, based on the melting depression of PBN. In nonisothermal crystallization investigations, the depression of the crystallization temperature of PBN depended on the composition of the blend and the cooling rate; the presence of PEI reduced the number of PBN segments migrating to the crystallite/melt interface. Melting, recrystallization, and remelting processes occurring during the DSC heating scan caused the occurrence of multiple melting endotherms for PBN. We explored the effects of various experimental conditions on the melting behavior of PBN/PEI blends. The extent of recrystallization of the PBN component during DSC heating scans decreased as the PEI content, the heating rate, the crystallization temperature, and the crystallization time increased. (C) 2004 Wiley Periodicals, Inc.