3D-Printed PLA Filaments Reinforced with Nanofibrillated Cellulose

In the current study poly(lactic acid) PLA composites with a 3 wt% and 5 wt% of nanofibrillated cellulose (NFC) were produced by 3D-printing method. An enzymatic pretreatment coupled with mechanical fibrillation in a twin screw extruder was used to produce high consistency NFC. Scanning electron microscopy (SEM) equipped with Fibermetric software, FASEP fiber length distribution analysis, Furrier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), tensile tests, impact tests and differential scanning calorimetry were used to characterize NFC and PLA/NFC composites. The results of the fiber length and width measurements together with the results of the SEM analysis showed that enzymatic hydrolysis coupled with a twin screw extrusion could effectively reduce the diameter and length of cellulose fibers. The produced NFC consisted of microand nanosized fibers entangled in a characteristic 3D-network. Based on the FT-IR analysis, no new bonds were formed during the enzymatic hydrolysis or fibrillation process. The TGA analysis confirmed that produced NFC can be used in hightemperature extrusion processing without NFC degradation. During the PLA/ NFC composites preparation the NFC agglomerates were formed, which negatively influenced PLA/NFC composites impact properties. The slightly improved tensile strength and elastic modulus were reported for all composites when compared to the neat PLA. The elongation at break was not affected by the NFC addition. No significant differences in thermal stability were detectable among composites nor in comparation with the neat PLA. However, the crystallinity degree of the composite containing 5 wt% NFC was increased in respect to the neat PLA.