Isodimorphism in Polyamide 56/Polyamide 66 Blends with Controllable Thermal and Mechanical Properties

The crystallization behaviors of polyamide 56/polyamide 66 (PA56/PA66) blends are investigated. Isodimorphism is first found in PA56/PA66 blends. The melting point, crystallization temperature, and crystallinity of the blends first decrease and then increase with the increase of PA66 content in the blends at the pseudo-eutectic point with ϕ66 = 0.5. The crystalline structure follows the dominant component in the blends. That is, PA56 phase and PA66 phase are obtained in the PA56-rich and PA66-rich blends, respectively, upon cooling the blends from the melting state. Both PA56 phase and PA66 phase are formed in PA56/PA66 blends at the pseudo-eutectic point upon cooling from the melting state. Fourier transformation infrared spectroscopy results indicate that the isodimorphic behavior is attributed to the hydrogen bonding interactions between PA56 and PA66 chains in the blends. Mechanical properties of the blends indicate that the elongation at break of the blends is tremendously enhanced without scarifying the strength and modulus of the materials. The isodimorphism of PA56 and PA66 provides a simple and promising approach for fabricating polymeric materials with versatile applications.