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Materials Science in Additive Manufacturing Natural composite filaments for 3D-Print

another study, the crystallization behavior was further polymeric wastes were developed by considering cocoa
investigated to probe into the effect of the addition of bean shells and recycled polypropylene, respectively.
plasticizer, namely polyethylene glycol (PEG), on the The combination of these two materials in the filament
mechanical and physical properties of filament materials production was found to result in a reduced shrinkage
produced through the fused filament fabrication (FFF) and warping behavior, thereby further enhancing the
technique. The addition of PEG plasticizer was found dimensional stability of the sample during the 3D printing
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to result in 3D-printed parts with crystallinity values process. 68
of up to 18% greater as compared to neat PLA, which Moreover, the development of biodegradable composites
also translated into improved mechanical and physical through 3D printing technology from the derivatives of
characteristics. The inferior mechanical properties natural fibers, namely cellulose, hemicellulose, and lignin,
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observed in neat poly(3-hydroxybutyrate) and PLA (PHB/ has also been realized in the recent past. For instance, the
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PLA) blends were found to be significantly improved optimum amounts of other naturally derived components,
upon the addition of plasticized blends based on esters of namely hemicellulose and lignin, which could be added in
citric acid. Moreover, the inclusion of such plasticizers the preparation of composite filament for 3D printing, were
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in the filament material blend led to a notable increase found to be 25% and 5%, respectively. 69,85 In other studies,
in the softening effect in the filament structure, thereby cellulose-based composite filament wire was successfully
resulting in a significant increase in their elongation at prepared by combining cellulose nanofiber (CNF) and
break. 64 PLA. In contrast to pure PLA filament wires, the inclusion
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4. Fibers and matrix selection for of cellulose reinforcement in the PLA-composite filament
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biodegradable NFRCFs wires was found to yield an increase in its tensile strength.
Besides improvement in their mechanical properties,
In previous studies, diverse types of natural fibers have been CNF-based biocomposite filament was also found to have
considered in the production of natural fiber-reinforced enhanced thermal stability. 67
composite filaments. Examples of such natural fibers
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consisted of rice straw, bamboo, hemp, sugarcane, and flax 4.1. Challenges of using natural fibers in NFRCFs for
fibers. 63,73,78-80 The fiber content by weight in the NFRCFs fused deposition modeling
was found to range between 15% and 30%. 63,73,78-80 Table 3 The challenges associated with the consideration of natural
summarizes the specification, composition, characteristics, fibers in the fabrication of biodegradable composite
and applications of commonly used composite-based non- filaments and their utilization are further discussed in this
biodegradable filament materials for 3D printing. Even section. One of the main concerns observed when dealing
though the filament material developed in these studies with natural fiber-based filament material during the
displayed satisfactory mechanical performance, they AM process is the lack of homogeneity in the deposited
were not fully biodegradable as a result of their polymeric layers. 73,86 The lack of homogeneity was found to arise due
matrix, which lacked the degradability trait. ABS is one to the combined effects of several factors originating from
such example that has poor degradable characteristics the printer hardware, printing parameters, and material
but nonetheless displays high tensile strength while being composition as outlined in Figure 7. For instance, it is to
resistant to physical impacts. 49,81 be noted that the homogeneity of 3D-printed structures
Besides the use of natural fibers, many studies have is normally affected by the print direction, which has a
considered fibers in powdered form as an alternative significant impact on their load-bearing capacity, thereby
21,87,88
reinforcement component for filament fabrication. One resulting in an orthotropic behavior.
example is bamboo-plastic composite wires, which were In terms of material composition, the inhomogeneous
developed through the FDM technique by considering mix of natural fiber composite for filament material can
printed wires made of bamboo flour, PLA matrix, and lead to a lack of homogeneity in the final product. As
plasticizers. Another powder-based material, namely reported in previous studies, it is unfeasible to achieve
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wood flour, was considered to produce wood flour-PLA a near-perfect homogeneous mixture of natural fiber
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filament at a composition ratio of 1:2.3. Before the composite for filament material in line with existing
filament fabrication, sieved wood flour from 140-mesh technologies. It is thus common to have an agglomeration
to 160-mesh size was mixed with PLA and distilled water, of the reinforcement components or particles in the
while experimental reagents, namely glycerol and TBC, composite mix, thereby further contributing to the
were considered and added as plasticizer. In another study, inhomogeneous and anisotropic nature of the 3D-printed
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3D printing composite filaments from agro-industrial and parts. Other issues that could potentially arise during the
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Volume 4 Issue 1 (2025) 8 doi: 10.36922/msam.8533