The crystallization ofPA11,PA12, and their random copolymers at increasing supercooling: From eutectic segregation to mesomorphic solid solutions

Abstract

The non-isothermal and isothermal crystallization of polyamide 11 (PA11), polyamide 12 (PA12), and their random copolymers was studied over the entire temperature range between the glass transition temperature and the high temperature melting point, using differential scanning calorimetry (DSC) and fast scanning calorimetry (FSC). The DSC and FSC thermal behavior was translated into structural evolutions, relying on earlier gathered X-ray based structural information and theoretical calculations. At low supercooling, the thermal behavior of the copolymers is typical for eutectic systems, involving monomeric segregation and crystallization into separate PA11 and PA12 crystals. Depending on the copolymer composition and the supercooling, the crystals are 4, 5, or 6 monomeric units thick. At very high supercooling, the PA11 and PA12 sequences cocrystallize into mesomorphic solid solutions with isodimorphic characteristics. At intermediate supercooling, the FSC heating traces following isothermal crystallization suggest that crystallization involves the simultaneous, isokinetic production of crystalline and mesomorphic patches. In this temperature range, lamellar crystals are 3 monomeric units thick throughout.