Revision as of 18:56, 14 April 2025

ABSTRACT

The adoption of bio-based materials as sustainable alternatives to fossil-derived options is becoming increasingly vital across industries. This research focuses on the development and performance characterization of Cellulose Acetate (CA), reinforced with natural fibres. CA, derived from renewable resources, offers good mechanical properties and excellent aesthetic quality, positioning it as a promising alternative to traditional petroleum-based polymers.

This study evaluates the influence of hemp natural fibres on CA composites. Special attention is given to the effect of these fibres on the overall performance of the compounds, including their aesthetic appeal, which is critical for consumer-facing applications.

To enable sustainable, efficient, and scalable production, the research utilizes Fused Granulated Deposition (FGF) technology to produce the demonstrators. This AM process allows the use of granulated feedstocks, reducing material costs and waste. Nonetheless, challenges such as layer adhesion and warping of CA during processing are addressed through a comprehensive parameter optimization, ensuring dimensional accuracy and high-quality output. The developed CA composites have been successfully validated through prototypes for construction sector such as green-wall components. These prototypes exhibited improved mechanical performance, aesthetic finishes and durability.

This work highlights a pathway for achieving circular economy goals through the integration of renewable materials and advanced technologies as an alternative to currently used materials and processes. By advancing in the understanding of natural fibre reinforcements and optimizing production processes, this research contributes to reducing the environmental impact of construction products while offering innovative solutions for bio-based composites in high-performance sectors, approaching them to the market.

KEYWORDS

Additive Manufacturing, 3D Printing, Biobased materials, Natural fibres.

INTRODUCTION

The use of bio-based materials as a sustainable alternative to fossil derivatives is growing in several industries, including the construction sector. The general objective of ATRIUM Project (Grant Agreement Nº 101135031) is to ensure a sustainable use of bio-based materials to produce bio-composites for the development of consumer-oriented products for the construction sector, transforming the EU construction industry and creating novel biotechnological value chains. In recent years, the pursuit of more sustainable manufacturing solutions has intensified, driving innovations that leverage bio-based polymers for additive manufacturing (AM) applications [1]. Among these polymers, Cellulose Acetate (CA) is a biobased polymer obtained from cellulosic biomass and stands out due to its renewability, reduced environmental impact, and potential biodegradability under certain conditions [2]. Tailoring natural fibres such as flax and hemp are getting more attention as alternative for synthetic fibres (like carbon fibres or glass fibres) because are relatively low cost, comes from renewable resources and have high specific strength and stiffness [3].

By blending CA with natural fibres such as hemp, sisal, or flax, researchers have achieved enhanced mechanical properties (e.g., higher tensile strength and stiffness) and improved thermal stability, all while reducing the overall carbon footprint of the material system. These Cellulose Acetate with natural fibres composites present an attractive alternative to conventional fossil-based plastics, aligning well with global goals for circular economy and lower CO₂ emissions.

Alongside material innovations, additive manufacturing processes, particularly Fused Granular Fabrication (FGF), have emerged as efficient, large-scale production methods that reduce waste and shorten lead times. In contrast to traditional filament-based 3D printing, FGF relies on pellet feedstocks, which allow the direct use of compounded Cellulose Acetate reinforced with natural fibres. By eliminating the need to convert pellets into filament, an additional heat cycle is avoided, thus reducing both costs and the risk of material degradation [4]. Nonetheless, to successfully integrate this technology into industrial contexts, a thorough optimization of process parameters is crucial to minimize warping, shrinkage and nozzle clogging resulting from fibre agglomeration.

Taken together, these novelty approach of bio-based polymer matrices and natural fibre reinforcement in combination with innovative AM technologies, offers compelling routes for sustainable product development. By fine-tuning material formulations, printing parameters and post-processing steps, these composites can deliver mechanical strength suitable for construction parts, while capitalizing on the ecological benefits inherent to cellulose-derived resins.

METHODS

For the construction sector, a composite of Cellulose Acetate and hemp fibres was developed to provide translucency, structural integrity and fire resistance, properties of considerable importance for architectural applications. Although bioPA was initially evaluated for this role, it proved unsuitable for FGF (Fused Granular Fabrication) due to its incompatibility with the pellet-based extruder format typically used in large-scale additive manufacturing. By contrast, Cellulose Acetate, synthesized from cotton-derived cellulose, acetic acid and a bio-based plasticizer, demonstrates excellent optical clarity and mechanical performance, making it an attractive matrix material. Hemp fibres, composed predominantly of cellulose, hemicellulose, pectin and lignin, enhance robust interfacial adhesion within the Cellulose Acetate matrix. Their measured dimensions, an average diameter of around 14.45 μm and a length of 0.50 mm, necessitate the use of nozzles wider than 0.4 mm to reduce clogging risks, underscoring the importance of carefully adjusting printing parameters.

To create the hemp-reinforced matrix, compounding through extrusion process was performed, introducing the fibres near the extruder’s nozzle to minimize thermal and mechanical degradation. An air-cooling belt replaced the conventional water bath to mitigate moisture absorption, ensuring consistent material quality and processability. Following this compounding step, the Cellulose Acetate with hemp fibres composite demonstrated favourable compatibility for both 3D printing and injection moulding. For high-volume production demanding quick throughput, stable dimensioning and reproducible quality, injection moulding remains advantageous despite restricting geometric freedom. Conversely, 3D printing accommodates intricate geometries, customized designs and prototypes, although at reduced production rates; this trade-off grants architects and engineers broader creative scope alongside resource-efficient fabrication.

In moving toward larger-scale additive manufacturing approaches, FGF was investigated as a precursor to BAAM (Big Area Additive Manufacturing). Pellets under 4 mm in size were processed at controlled speeds and temperatures to preserve fibre integrity and avoid thermally induced degradation of the Cellulose Acetate matrix. A slightly elevated extrusion flow was employed, facilitating improved interlayer adhesion crucial for sustaining mechanical loads in the final parts. Multiple nozzle diameters, ranging from 0.55 mm to 2.5 mm, were tested, each demanding optimized print speeds, flow rates and layer heights to maintain consistent print quality. The capacity to modify nozzle size and operating parameters allows manufacturers to target different use cases: smaller nozzles yield finer features and smoother surfaces but reduce throughput, whereas larger nozzles enable faster builds but may compromise resolution.

Extensive mechanical evaluations of both the virgin Cellulose Acetate and hemp-fibre–reinforced materials were conducted, focusing on tensile and flexural strength in accordance with standardized protocols. Comparisons of injection-moulded and 3D-printed samples highlight the expected superior performance of injection-moulded parts, driven by their uniform microstructure and well-established processing conditions. Nonetheless, 3D printing with smaller nozzle diameters (0.55–0.8 mm) exhibited commendable mechanical properties, approaching those of injection-moulded components.

We also tested flexural strength. Again, injection-moulded parts were strongest, but the 3D-printed ones, especially with mid-sized nozzles, were strong enough for many construction-related applications.

When comparing virgin Cellulose Acetate to hemp-filled acetate, a slight reduction in flexibility was noted alongside a significant increase in stiffness. This trade-off is advantageous where greater rigidity is desired, particularly in construction contexts.

From a design perspective, the translucent quality of Cellulose Acetate and the reinforcement afforded by hemp fibres make this material especially well-suited for applications such as modular facades, interior partitions, or decorative panels where both aesthetic appeal and structural robustness are desired. The inherent tunability of additive manufacturing, coupled with the sustainability benefits of using cellulose-based polymers, positions these biocomposites as promising candidates for future innovations in sustainable construction and advanced building technologies.

In practice, these biobased polymer composites were employed to design and manufacture a modular green wall through 3D printing, showcasing the translucent, fire-resistant and environmentally friendly characteristics of CA combined with hemp.

Future work will involve improving formulations for better mechanical performance and moisture stability, scaling up industrial production and testing biodegradability under real operating conditions.

A modular green-wall system was designed and successfully printed using the Cellulose Acetate and hemp composite, taking advantage of FGF technology for large-format components. The design approach allowed for customizable, interlocking modules that can be easily scaled or rearranged according to specific architectural requirements. By utilizing natural fibres within a bio-based polymer matrix, the resulting green-wall combines structural stability with environmental sustainability. Furthermore, the adaptable nature of 3D printing enabled faster prototyping and design iterations, making it suitable for both small-scale installations and future large vertical gardens.

In future research, large-format equipment, such as the CEAD S25 extruder mounted on a robotic arm, will be employed to print larger-scale modules capable of accommodating a greater number of planting pots in a single printed piece.

By validating this material approach in sectors such as construction and aligning with the EU’s Green Deal objectives for a circular economy, it becomes increasingly clear that biobased polymers reinforced with natural fibres can effectively replace fossil-based plastics while supporting sustainable and large-scale manufacturing.

AKNOWLEDGMENT

Author Contributions: All co-authors have covered all tasks of this research.

Funding: The authors gratefully acknowledge the European commission for support through the financial aid under the framework Horizon-CL6-2023-CircBio-01-8 program through the project ATIRUM, this project received funding from the European Union’s Horizon Europe Framework Programme under Grant Agreement No 101135031and co-funded by UKRI under the UK government’s Horizon Europe funding guarantee

Conflicts of Interest: The authors declare no conflict of interest.

BIBLIOGRAPHY

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[2] Paggi, R.A., Salmoria, G.V., Ghizoni, G.B. et al. Structure and mechanical properties of 3D-printed cellulose tablets by fused deposition modeling. Int J Adv Manuf Technol 100, 2767–2774 (2019). https://doi.org/10.1007/s00170-018-2830-z

[3] Disha Deb, J.M. Jafferson, Natural fibers reinforced FDM 3D printing filaments, Materials Today: Proceedings, Volume 46, Part 2, 2021, Pages 1308-1318, ISSN 2214-7853, https://doi.org/10.1016/j.matpr.2021.02.397

[4] Minetola, P., Fontana, L., Arrigo, R., Malucelli, G., Iuliano, L. (2021). Mechanical Performance of Polylactic Acid from Sustainable Screw-Based 3D Printing. In: Scholz, S.G., Howlett, R.J., Setchi, R. (eds) Sustainable Design and Manufacturing 2020. Smart Innovation, Systems and Technologies, vol 200. Springer, Singapore. https://doi.org/10.1007/978-981-15-8131-1_47