Manipulating phase structure of biodegradable PLA/PBAT system: Effects on dynamic rheological responses and 3D printing

Poly (lactic acid) (PLA), as a biodegradable thermoplastic polyester, has many advantages but a crucial shortcoming of brittleness. It has been recognized that blending with biodegradable poly (butylene-adipate-co-terephthalate) (PBAT) is an effective way to toughen PLA. In this paper, an efficient compatibilizer of PLA-g-GMA (PLA grafted with glycidyl methacrylate) was prepared by melt grafting and then introduced to compatibilize the two phases in PLA/PBAT blends. The dynamic rheological responses were investigated to explore the effects of PLA-g-GMA on the rheological behaviors of PLA/PBAT. Furthermore, the mechanical properties of 3D printed PLA/PBAT/PLA-g-GMA specimens in longitudinal and transverse deposition were examined to compare with that by injection molding so as to reveal the functions of compatibilizer in 3D printing. The results show that the compatibilizer significantly improved the compatibility of PLA and PBAT, and the interface binding capacity of PLA and PBAT was positively related to the content of compatibilizer. Dynamic rheological analysis showed that when the content of compatibilizer reached 10 wt%, the blends has the maximum degree of molecular chain entanglement, complex viscosity and melt strength. It was also found that the compatibilizer significantly improved the interfacial adhesion between layers of 3D printing specimens. In addition, the filament orientation with microchannels was key factor affecting performance improvement of 3D printing specimens as well. Consequently, the tensile strength of blend PLA/PBAT = 70/30 with 10 wt% compatibilizer PLA-g-GMA up to 42.6 MPa and elongation at break over 200%, which is not only higher than that of the injection sample (33.7 MPa), but also higher than the maximum value reported in the literatures ever read.