The semicrystalline morphology of aliphatic-aromatic polyamide blends

The morphology of a series of melt-miscible blends based on the combination of (crystalline) polyamide (PA) 4,6 and (amorphous) PA 61 has been investi gated as a function of blend composition and thermal history. Wide-angle X- ray scattering (WAXS) was used to determine the unit cell structure and cry stallinity index in PA 4,6 and the blends: the introduction of PA 6I result ed in no change in unit cell parameters and a monotonic decrease in bulk cr ystallinity. Dynamic mechanical studies revealed the coexistence of two amo rphous phases in the crystallized blends: a mixed phase held between the cr ystal lamellae (interlamellar) and a PA 6I-rich phase excluded to interfibr illar and interspherulitic regions. There was no evidence of a separate cry stal-amorphous interphase layer comprised of pure PA 4,6. Transamidation re actions over longer melt times led to the apparent homogenization of the tw o amorphous populations owing to the formation of increasingly random copol ymers. (C) 2000 Elsevier Science Ltd. All rights reserved.