Enhancing PLA Toughness with Minimal PBAT Additives: Unveiling the Role of Phase Interface and Particle Size through In Situ Reactive Compatibilization

Abstract

Polylactide (PLA) was melt blended with low amounts of poly(butylene adipate-co-terephthalate) (PBAT) using a simple reactive extrusion process herein, aiming to address the inherent brittleness of PLA without significantly compromising its stiffness. PLA/PBAT (90/10) blends with a small amount of peroxide (0.02 phr) and a second crosslinker agent TAIC (triallyl isocyanurate) were produced to explore the structure-performance relationship evolution in reactive extrusion. The results showed that the PLA blend with an appropriate amount of TAIC (i.e., 1.0 phr) exhibited a remarkable increase in elongation at break, reaching as high as 76.8%, which was 22 times higher compared to pure PLA and 6.8 times higher than unmodified PLA/PBAT blends. Furthermore, the sample with high elongation also demonstrated a high stiffness, boasting a Young's modulus of 1.6 GPa and a yield strength of 43 MPa. It was evident that both interfacial adhesion and PBAT size significantly influenced the stretchability of the PLA/PBAT blends. The combination of enhanced compatibility and optimized PBAT phase size of approximately 1.0 µm worked synergistically to enhance the toughness of PLA. Notably, either larger or smaller particle sizes did not contribute favorably to enhancing the toughness of PLA, even if compatibility was improved. The addition of small amounts of TAIC successfully reduced the PBAT phase size but did not enhance compatibility, leading to subpar mechanical performance. Conversely, higher TAIC contents resulted in over-crosslinking, despite considerable improvements in compatibility. This study offers a versatile, scalable, and practical method to prepare fully biodegradable PLA blends with high toughness.