Plasticizing Modification of Bio-Based Polyamide 4 With Lewis Acids and Its Nonisothermal Crystallization Kinetics

The plastic pollution crisis highlights the urgent demand for bio-based biodegradable polymers. Polyamide 4 (PA4) is a promising candidate, yet its application is severely limited by an extremely narrow thermal processing window (≈2°C). This work broadens this window through Lewis acid (LA) complexation modification and investigates the influence of CaCl 2 on the crystallization kinetics of PA4. Results show that specific LA, particularly CaCl 2 , acts as multifunctional modifiers. CaCl 2 interacts with the amide groups of PA4 and modifies the intermolecular hydrogen-bonding network. This unique interaction significantly increases ductility (elongation at break rises from 99% to 211%) while maintaining tensile strength and approximately maintaining the thermal degradation temperature, and most critically, broadens the thermal processing window from 2°C to 24°C primarily by lowering the melting temperature. Advanced nonisothermal crystallization kinetics analysis reveals a novel concentration-dependent dual mechanism of CaCl 2 : chain-complexation dominates at low loadings, while heterogeneous nucleation prevails at 7 wt.%, substantially reducing the crystallization activation energy (Δ E = −23.36 KJ mol −1 ). This clarifies the precise pathway for regulating PA4 crystallization via additives. In summary, this study elucidates the precise pathway for regulating PA4 crystallization via additives, providing a reference for the thermal processing applications of materials with limited thermal processing windows. Graphical We demonstrate that Lewis acid complexation, especially with CaCl 2 , broadens the processing window of bio-based polyamide 4 from 2°C to 24°C primarily by lowering the melting temperature while approximately maintaining the thermal degradation temperature. This modification also maintains tensile strength while revealing a concentration-dependent mechanism in crystallization kinetics, offering new insights for preparing high-performance biodegradable polymers.