Toughening of Self-Reinforced PLA Films Using PLA Nanofiber Mats and Oriented PLA Tapes As Interlayers

Self-reinforced poly(lactic acid) composite (SRPLA) offers advantages in terms of convenient recycling due to its mono-material nature, potential biodegradability, and biocompatibility. Moreover, SRPLA has shown the ability to overcome the inherent brittleness of PLA. To deepen our understanding of how different types of reinforcements and process parameters can affect tensile properties, particularly tensile toughness, SRPLA has been prepared based on oriented tapes (ot-SRPLA) as well as nanofiber mats (nf-SRPLA) using a film-stacking and hot-compaction approach. A considerable improvement was observed in tensile strength, modulus, and toughness at the optimum consolidation temperature and time. Specifically, the tensile toughness of nf-SRPLA increased approximately threefold at a very low nanofiber loading of 0.56 wt%, while the toughness of ot-SRPLA more than doubled at a tape mass fraction of 36 wt%. In terms of toughening mechanisms, the presence of the nanofibers slowed down crack propagation through crack branching, deviation, and fiber bridging in nf-SRPLA, whereas the predominant toughening mechanisms were interlayer debonding and tape pull-out for ot-SRPLA.