PVA-CNCs composite electrospun nanofibers for poly(lactic acid) polymer reinforcement

In this study, poly(vinyl alcohol) (PVA) in a water solution was mixed with CNC suspensions in 4:1 and 3:2 weight ratios (w/w) and electrospun (ES) into aligned composite fiber mats. The electrospun mats were mechanically cut into high aspect ratio nanofibers (PVA:CNC-nf) and used as reinforcement in melt compounded thermoplastic poly(lactic acid) (PLA). A control PLA composite, containing neat electrospun PVA fibers (PVA-nf) and electrosprayed CNC nanoparticles (CNC-np), was produced for each composite fiber ratio. The electrospun nanofibers (ESNFs) were observed to maintain their morphology without exhibiting agglomeration or void formation in the PLA matrix. Composites containing 15 wt.% 4:1-nf improved tensile strength and stiffness of the PLA by 21% and 30%, while reducing strain at break by 7%, and increased PLA impact strength by 54%. In comparison, the 12 wt.% neat PVA-nf improved the PLA tensile strength and stiffness by 19% and 8%, respectively, while increasing tensile strain at break by 24% and impact strength by 30%. Toughness analysis indicated that the neat PVA-nf improved PLA specific tensile strength, despite the 4:1-nf absorbing more impact energy. Flexural strength improved slightly with the 3:2-nf, but flexural stiffness generally decreased, apart from 15% and 7.5% filled 4:1-nf and 3:2-nf filled PLA composites. Mechanical improvements were attributed to the electrospun reinforcement fibers’ nanometer dimensions and interfacial compatibility, based on by the shift to bound hydroxyl groups detected in the Fourier transform infrared spectroscopy (FTIR) analysis for the PLA composites.