Tensile Behavior and Phase Separation Structure of Aliphatic Polyketone/Polyamide 6 Polymer Alloy

TEM and AFM-IR images of the polymer alloys of aliphatic polyketone (PK) and polyamide 6 (PA) revealed that the phase separation structures of these alloys were a sea-island structure, a three dimensional co-continuous structure of PA-rich and PK-rich phases, and the inversion structure of the sea-island structure. The PK-rich phase contained a network of PK lamellae. Whereas a simple mixing rule on the PA volume fraction (φPA) dependence of the elastic modulus (E) of dry polymer alloy was applied, a unique mixing rule which took the moisture absorption rate of wet polymer alloy into consideration was found. In particular, K 60 A 40 (PK 60% by mass ＋ PA 40% by mass, φPA ＝ 42%) having a co-continuous structure showed a clear yield point in the dry state, whereas a yield point was not observed in the water-absorbed state. Also, regardless of drying and water absorption, the maximum stresses and strains were almost the same. In the former, the lamellar network was disrupted and disappeared immediately after the yield point, whereas in the latter case, the lamellar network was greatly deformed without significant damage up to the point of rupture. It is considered that the tensile behavior of the latter contributes to improved mobility of PA molecular chains by water absorption, enhancement of interfacial bonding of PK/PA phases by hydrogen bonding, and reinforcement effect by lamellar network.