Crystallization of Polyamide 66 in Blends with Polyamide 6

This is the authors' abstract. We don't add key points for this paper.

Crystallization of miscible blends of polyamide 66 (PA 66) and polyamide 6 (PA 6) was systematically investigated to understand how blend composition influences crystallization kinetics and nucleation mechanisms. Unlike our previous work on PA 66–PA 6I/6T blends (Macromolecules 2025, 58, 15, 8151–8164), where only one component crystallizes and two polymers differ significantly in glass transition temperature (Tg), the current system involves two crystallizable components with nearly identical Tg. Thermal, spectroscopic, and morphological analyses across a broad temperature range reveal that detectable PA 6 crystallization is absent at 10–20 wt % PA 6, while at higher PA 6 fractions the results are consistent with concurrent PA 66 and PA 6 crystallization. No resolvable sequential crystallization is detected under the isothermal conditions studied, while a measurable mutual suppression of crystallization is observed, particularly at lower PA 6 concentrations. Increasing PA 6 content leads to a progressive slowdown in crystallization kinetics and a clear downward shift in crystallization temperature of the blends. The temperature marking the transition from homogeneous to heterogeneous nucleation is shown to be continuously tunable through blend composition from 135 °C in neat PA 66 to near 125 °C in 10–20 wt % blends, 110–120 °C in 30–80 wt % blends, and below 110 °C in high-PA 6-content blends and neat PA 6. This work demonstrates a polymer blend system in which crystallization kinetics can be continuously tuned across the entire temperature range, while the nucleation mechanism transition temperature is systematically adjustable between the values observed in the two neat components. Beyond its industrial relevance for processing optimization, the PA 66–PA 6 system serves as a powerful experimental platform for probing the kinetic origins of nucleation pathway selection in semicrystalline polymers.