Melting behavior and nonisothermal crystallization kinetics of polyamide 6/polyamide 66 molecular composites via in situ polymerization

The melting behavior and nonisothermal crystallization kinetics of pure polyamide 6 (PA 6) and its molecular composites with polyamide 66 (PA 66) were investigated with differential scanning calorimetry. The PA 6/PA 66 composites had one melting peak, whereas the coextruded PA 6/PA 66 blends had two melting peaks. With the addition of PA 66 to PA 6 via in situ anionic polymerization, the melting temperature, crystallization temperature, and crystallinity of PA 6 in the composites decreased. The half‐time of nonisothermal crystallization increased for a PA 6/PA 66 molecular composite containing 12 wt % PA 66, in comparison with that of pure PA 6. The commonly used Ozawa equation was used to fit the nonisothermal crystallization of pure PA 6 and its composites. The Ozawa exponent values in the primary stage were equal to 1.28–3.03 and 1.28–2.97 for PA 6 and its composite with 12 wt % PA 66, respectively, and this revealed that the mechanism of primary crystallization of PA 6 and PA 6/PA 66 was mainly heterogeneous nucleation and growth. All the results indicated that the incorporation of PA 66 into PA 6 at the molecular level retarded the crystallization of PA 6.