A New Strategy for the Preparation of Fully Biobased and Biodegradable Polylactic Acid with Both High Rigidity and Flexibility

Tougheners are crucial for polylactic acid (PLA) because of its inherent brittleness. Among the many available tougheners, biobased and/or biodegradable tougheners are the primary choice. However, increasing PLA toughness typically leads to a trade-off with reduced rigidity or modulus. In this study, biobased and biodegradable thermoplastic vulcanizates (BBTPVs), made from PLA and a polyester elastomer (BBPE), are developed for toughening of PLA. The PLA phase in BBTPV ensures high compatibility with the PLA matrix, while the BBPE rubber phase, with its adjustable cross-linking degree and particle size, allows for controlled stress dissipation. Further, fully biobased and biodegradable PLA composites exhibiting excellent performances are prepared. The elongation at break and notched impact strength of the PLA–BBTPV composite increase by 31 and 12 times, respectively, compared with pure PLA, while its tensile strength remains high (44.5 MPa). This study offers a new approach for preparing fully biobased and biodegradable PLA with high rigidity and flexibility.