Effects of 1D and 2D nanofillers in basalt/poly(lactic acid) composites for additive manufacturing

In this work, basalt microfiber reinforced poly(lactic acid) (PLA) composites filled with talc nanoplatelets (2D) and sepiolite nanofibers (1D) were prepared at different compositions and tested to assess the effects of filler geometry. Thermal analysis results show that crystallinity of amorphous PLA can be enhanced up to 24% by adding basalt and talc. Thermal stability of PLA is increased by basalt microfibers whereas talc and sepiolite prompted early degradation in binary composites. In ternary systems, i.e. PLA/basalt/talc and PLA/basalt/sepiolite, thermal stability was further increased. Mechanical tensile and flexural properties were remarkably increased for a specific composition basalt (30 wt%) and talc (10 wt%) with a final enhancement of 176% and 261% for modulus and 46% and 43% for strength respectively in tensile and bending configuration. For the composition, the coefficient of thermal expansion is significantly reduced up to 54% of the corresponding pristine PLA value. The increase of thermal conductivity is mainly related to the presence of 1D sepiolite, with a variation of ~54% for the 10 wt% PLA/sepiolite binary system. Finally, a significant increment of impact property was observed by unnotched Charpy impact tests for talc (+97%) and basalt (+140%) composites.