Analysis of dual melting behavior in cold-crystallized poly(ether diphenylether metaketone)

By focusing on cold-crystallized poly(ether diphenyl ether metaketone) (PEK m), a more in-depth understanding of the nature of the crystalline morpholo gy has been gained, which may lead to thorough mechanisms for interpreting the observed thermal behavior in PEKm. Apparently, cold-crystallized PEKm c ontaining initially only a single PI crystal can exhibit dual melting peaks (300 and 320 degreesC), with the second high-melting peak corresponding to the P2 crystal that was subsequently formed via PI melting/repacking durin g the scan. However, dual morphism (preexisting PI and P2 crystals) could b e intentionally introduced into PEKm if it was cold-crystallized at tempera ture schemes of decreasing order. The PI and P2 crystals possess the same u nit cells (orthorhombic) and thus they differ only in the lamellae populati ons. The dual lamellar morphism in this PEKm sample also exhibited similar dual melting peaks during scanning, which correspond to melting of the indi vidual PI and P2 in a sequential order. This study has thus provided import ant clues in and shed new light on the interpretation of multiple melting w ith respect to polymorphism in polymers. Relationships between the low-melt ing and high-melting lamellae in cold-crystallized polyketone polymer have been thoroughly explored.