Towards Superior Biopolymer Blends: Tuning the Micro-/Nano-structure of Poly(L-lactide) Composites for High-Performance Applications

A.V. Tuccitto, A. Anstey, N.D. Sansone, C.B. Park, P.C. Lee
University of Toronto,

Keywords: micro-/nano-structuring, biopolymer blends


Poly(L-lactide) (PLLA) is a bio-based and compostable plastic with significant potential for replacing petroleum-based plastics. However, its poor crystallization kinetics, melt strength and low thermal resistance limit PLLA’s processability and application in high-performance components. Nevertheless, these issues can simultaneously be overcome by blending PLLA with functional fillers, including carbon fiber, glass fiber, and other polymeric materials. For example, PLLA can be melt-blended with poly(D-lactide) (PDLA) to form stereocomplex crystallites with a melting temperature about 50°C above that of neat homopolymers. These stereocomplex crystallites have a strong nucleating effect and remarkably enhance PLLA’s melt strength, while imparting enhanced thermal resistance. Moreover, if drawn from the melt-state, the stereocomplex crystallites can be transformed into nanofibers, improving the tensile strength and modulus of blends. Combining material optimization and unique micro-/nano-structuring technologies, micro-/nano-structured biopolymer composites can be fabricated by in situ fibrillation and coextrusion technologies, allowing direct control of blend micro-/nano-structure, and thus final properties. The outcome of this research program will be a comprehensive understanding of constrained micro-/nano-structure evolutions, interphase compatibility, and the effects of embedded nanofibers on the final morphologies and properties of PLLA blends, which will enable the creation of the next generation of biopolymer composites.