Abstract
Polylactic acid (PLA) is one of the most suitable materials for 3D printing. Blending with nanoparticles improves some of its properties, broadening its application possibilities. The article presents a study of composite PLA matrix filaments with added unmodified and lignin/polymerised lignin surface-modified nanofibrillated cellulose (NFC). The influence of untreated and surface-modified NFC on morphological, mechanical, technological, infrared spectroscopic, and dynamic mechanical properties was evaluated for different groups of samples. As determined by the stereo and scanning electron microscopy, the unmodified and surface-modified NFCs with lignin and polymerised lignin were present in the form of plate-shaped agglomerates. The addition of NFC slightly reduced the filaments’ tensile strength, stretchability, and ability to absorb energy, while in contrast, the initial modulus slightly improved. By adding NFC to the PLA matrix, the bending storage modulus (E’) decreased slightly at lower temperatures, especially in the PLA samples with 3 wt% and 5 wt% NFC. When NFC was modified with lignin and polymerised lignin, an increase in E’ was noticed, especially in the glassy state.
Highlights
Three-dimensional (3D) printing technology ( known as additive manufacturing (AM)) is constantly expanding, mainly due to the advantages in the rapid and cost-effective production of complex, tailored-shape products [1,2]
For a better understanding of the properties of composite filaments produced in our research, the used unmodified nanofibrillated cellulose (NFC), and NFC with lignin and with a polymerised ligninmodified surface (NFC + L and NFC + PL, respectively) were observed by SEM
A common phenomenon that occurs during the freeze-drying of the nanofibrillated cellulose dispersion is agglomeration, which was proved by Peng et al [22]
Summary
Three-dimensional (3D) printing technology ( known as additive manufacturing (AM)) is constantly expanding, mainly due to the advantages in the rapid and cost-effective production of complex, tailored-shape products [1,2]. In order to meet the demands of an increasingly challenging market (automotive, aerospace, biomedical products, architectural and ornamental products, and other fields of application) [2], different materials have been used; e.g., polymers, metals, resins, ceramic, sand, wax, etc. Its advantages are a slow degradation rate, hydrophobicity and chemical inertness [6], high strength, and high modulus [7]. Besides its advantages, it has some drawbacks; e.g., inherent brittleness—low toughness, low thermal stability—its hydrolysable backbone can be degraded by thermal processing and hydrolytic reactions, which results in a decrease of molecular mass and worsening of mechanical properties [8,9]. Reinforced with different types of nanofillers, properties of PLA nanocomposites could be improved; cellulosic nanomaterials, among which is nanofibrillated cellulose (NFC), attract a lot of attention
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