Evaluation of the Self-Healing Behaviour of Structural Polyamide 6 (PA6)/Poly(butylene-adipate-terephthalate) (PBAT) Blends

In this study, polyamide 6/poly(butylene-adipate-terephthalate) (PA6/PBAT) blends, potentially applied as novel self-healing matrices for structural composites, were developed and characterized. The blends were melt-compounded at different PBAT amounts (from 20 up to 50%vol) and hot pressed. Rheological analysis showed a decreased in the storage and loss moduli of PA6 with PBAT, maintaining viscosity levels suitable for conventional melt-processing operations. FT-IR and FESEM observations demonstrated the formation of blends with immiscible morphology and uniformly dispersed PBAT domains. Quasi-static tensile tests showed a progressive decrease in tensile modulus and strength with PBAT, but a strong improvement in the elongation at break. The blend containing 30%vol PBAT showed satisfactory stiffness (2.2 GPa), strength (42 MPa) and elongation at break (10.5%) compared to PA6 (3.4 GPa, 62 MPa and 5.2%), thus this formulation was selected for self-healing assessment. Its repair efficiency was quantified as recovery of the fracture toughness (KIC) after a thermal treatment at 150 °C for 30–120 min under pressure from 1–3 MPa. The highest healing efficiency (28%) was obtained after 120 min under 1 MPa, conditions at which the PBAT reduced its viscosity and flowed across the crack interface. Therefore, the blend with 30%vol PBAT will be considered in future for the preparation of multifunctional composites with thermal self-healing capability.