Latest revision as of 13:43, 21 July 2025

INTRODUCTION

The use of bio-based materials as sustainable alternatives to fossil derivatives is rapidly growing in various industries, including construction. The general objective of the ATRIUM Project (Grant Agreement Nº 101135031) is to ensure a sustainable use of bio-based materials to produce biocomposites for the development of consumer-oriented products for the construction sector, transforming the EU construction industry and creating novel biotechnological value chains. This study was conducted within the scope of the ATRIUM project, specifically addressing the development, validation, and demonstration of modular green-wall systems using bio-based composites reinforced with natural fibres.

In recent years, the pursuit of more sustainable manufacturing solutions has intensified, driving innovations that leverage bio-based polymers for AM applications [1]. Among these polymers, CA is obtained from cellulosic biomass and stands out due to its renewability, reduced environmental impact, and potential biodegradability under certain conditions [2]. Natural fibres such as flax and hemp are gaining attention as alternatives to synthetic fibres (e.g., carbon or glass fibres) because they are relatively low-cost, derived from renewable resources, and have high specific strength and stiffness [3].

Blending CA with natural fibres such as hemp, sisal, or flax has led to enhanced mechanical properties (e.g., higher tensile strength and stiffness) and improved thermal stability, while also reducing the overall carbon footprint of the material system. These composites align well with global circular economy goals and lower CO₂ emissions.

Alongside material innovations, AM processes (particularly FGF) have emerged as efficient large-scale production methods that reduce waste and shorten lead times. Unlike filament-based 3D printing, FGF relies on pellet feedstocks, which allow direct use of compounded CA reinforced with natural fibres. By eliminating the need to convert pellets into filament, an additional heat cycle is avoided, reducing both costs and the risk of material degradation [4]. However, successful industrial implementation requires careful optimization of process parameters to minimize warping, shrinkage, and nozzle clogging due to fibre agglomeration.

This combined approach of bio-based polymer matrices, natural fibre reinforcement, and advanced AM technologies offers promising routes for sustainable product development. By fine-tuning material formulations, printing parameters, and post-processing, these composites can deliver mechanical performance suitable for construction parts while capitalizing on the ecological benefits inherent to cellulose-derived resins.

METHODS

For the construction sector, a composite of CA and hemp fibres was developed to provide translucency, structural integrity, and fire resistance—properties of considerable importance for architectural applications. Although bio-based Polyamide (bioPA) was initially evaluated for this role, it proved unsuitable for FGF due to its incompatibility with the pellet-based extruder format typically used in large-scale AM. By contrast, CA 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 CA matrix. Their measured dimensions—average diameter ~14.45 μm and length ~0.50 mm—necessitated the use of nozzles wider than 0.4 mm to reduce clogging risks, underscoring the importance of carefully adjusting printing parameters.

Compounding through extrusion 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.

Pellets under 4 mm were processed at controlled speeds and temperatures to preserve fibre integrity and avoid thermally induced degradation. A slightly elevated extrusion flow facilitated improved interlayer adhesion crucial for sustaining mechanical loads. Multiple nozzle diameters (0.55–2.5 mm) were tested, with each requiring optimized print speeds, flow rates, and layer heights.

Mechanical evaluations were conducted on both virgin CA and hemp-fibre–reinforced materials, focusing on tensile and flexural strength in accordance with standardized protocols.

RESULTS

Comparisons between injection-moulded and 3D-printed samples confirmed the superior performance of injection-moulded parts due to their uniform microstructure. Nonetheless, 3D printing with smaller nozzle diameters (0.55–0.8 mm) demonstrated 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 CA 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 CA and the reinforcement provided by hemp fibres make this composite particularly suitable for modular facades, interior partitions, and decorative panels requiring aesthetic appeal and structural robustness.

A modular green-wall system was designed and successfully printed using this composite, taking advantage of FGF technology for large-format components (Figure 4). The interlocking modules demonstrated scalability and adaptability for architectural requirements.

CONCLUSIONS

This study validates the feasibility of combining CA and hemp fibres in FGF-based manufacturing for construction applications. The resulting biocomposites demonstrated mechanical properties comparable to conventional materials while offering significant advantages in terms of sustainability, reduced carbon footprint, and aesthetic versatility.

The research confirmed that hemp fibre reinforcement increases the stiffness and strength of CA parts, which is particularly beneficial for structural and semi-structural applications such as modular façades and interior partitions. However, it also highlighted the importance of carefully balancing nozzle diameter, extrusion flow, and printing speeds to minimize defects such as warping and fibre agglomeration.

Moreover, the successful fabrication of modular green-wall prototypes illustrates the practical potential of these biocomposites to be integrated into scalable architectural solutions. The adaptability of FGF technology enabled the production of large-format components with customizable geometries, aligning with the growing demand for individualized and sustainable construction elements.

Future work will focus on several key areas. First, optimizing the formulations to further improve mechanical performance and moisture stability will be essential to broaden the range of end-use applications. Second, scaling up production to an industrial level will require process validation under real manufacturing conditions and additional assessments of long-term durability and biodegradability. Third, expanding the scope of testing to include fire resistance, acoustic properties, and life cycle assessment will strengthen the evidence base for adopting these materials in mainstream construction projects.

Overall, this work provides a clear pathway for replacing fossil-derived plastics in the built environment while supporting circular economy objectives and advancing the development of high-performance bio-based materials.

AKNOWLEDGMENTS

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