Compatibilization of PLA/PBAT blends with epoxidized canola oil for 3D printing applications

Abstract

Poly(lactic acid) (PLA) is a bioderived and biodegradable thermoplastic biopolyester that is widely used in 3D printing. Although PLA is an excellent example of a high-performance naturally derived building block that has found practical applications in a number of different markets, PLA-printed parts often exhibit poor toughness and brittle mechanical behavior. In order to improve the outlook of PLA in material extrusion (MEX) 3D printing applications, this work aims to develop impact-modified and fully biodegradable blends comprising PLA and poly(butylene adipate-co-terephthalate) PBAT, compatibilized with epoxidized canola oil (ECO). Importantly, our approach is fundamentally different from previous examples, which typically rely on non-bioderived or non-biodegradable compatibilizers to improve blend performance. Here, blends of PLA and PBAT having various ratios were prepared by melt compounding with 5 phr ECO. Importantly, the addition of ECO did not significantly alter the rheological properties of the blends, but exerted a plasticizing effect reducing the glass transition and cold crystallization temperatures of the blends. Microstructural and mechanical analyses of compression-molded samples revealed uniform dispersion of PBAT domains within the PLA matrix in the presence of ECO, leading to a 62% and 106% increase in impact strength for blends containing 20 and 30 wt% PBAT, respectively, as compared to non-compatibilized blends. Based on significant improvements in impact strength, 70/30 PLA/PBAT blends with 5 phr ECO were chosen for 3D printing experiments. Parts printed from PLA/PBAT blends displayed poor fusion between strands, resulting in voids and brittle failure during tensile testing. In the case of compatibilized blends, ECO incorporation facilitated fusion between neighboring strands, enhancing ductility during tensile testing. Therefore, we demonstrate that the addition of ECO to PLA/PBAT blends not only enhances compatibilization but also improves printability and strand healing during MEX 3D printing. We anticipate that the results presented here could pave the way for the development of high-performance and fully biodegradable materials and blends through a variety of extrusion-based processing methods.