Miscibility in two blend systems of homologous semicrystalline aryl polyesters involving poly(trimethylene terephthalate)

The miscibility in the pairs of homologous series of semicrystalline polyesters: poly(trimethylene terephthalate) (PTT) and poly(ethylene terephthalate) (PET) and poly(trimethylene terephthalate) (PTT) and poly(butylene terephthalate) (PBT), respectively, were investigated as model systems. In this study, two binary blend systems each containing two semicrystalline aryl-polyesters differing by the number of methylene units, were found to be fully miscible (in absence of trans-esterifications) in accordance with criteria of microscopy morphology and thermal transition. In addition, only a single composition-dependent T-cc was taken as a valid supportive evidence for miscibility in blends of two crystallizable polymers. The claimed miscibility applied to the quenched state of the blends, and not the crystallized domain involving the crystal cells in the crystalline regions. The crystal morphology evidence showed that the unit cell types in the miscible blends remained individually different, and co-existed in common spherulites.