ABSTRACT
This chapter focuses on a wide and remarkably creative array of commercial and experimental sustainable feedstocks for additive manufacturing (AM) made of biobased and non-biobased polymers combined with fillers from plants (grain, flax, harakeke, hemp, rice, sisal, etc.), trees (coconut, cork, resins, etc.) and even beer and coffee waste. The fillers described are mostly derived from cork, natural fibers (sisal, flax, hemp, and harakeke), nuts, algae, grain, rice, and tree resins. They possess the advantage of being biobased, biodegradable, inexpensive, lightweight, and enabling products with new aesthetic features. The AM feedstocks illustrated in the present chapter are employed for fused filament fabrication and binder jetting. Source, properties, and non-AM uses are reported for all fillers, along with market data when available.
This chapter opens with feedstocks filled with cork, flax, and hemp because there exist commercial versions of them, and shifts to experimental feedstocks filled with other plant-derived ingredients: harakeke, nut shells, rice husk, and so on. Suppliers of the above commercial composite filaments seem to focus mostly on the appearance of their products, because no mechanical properties are disclosed for all their filaments. Most commercial and experimental composites for AM made of feedstocks derived from natural fibers and trees do not outperform their matrices in mechanical performance, indicating that more R&D is required to elucidate the factors improving the composites’ properties, such as f.e. filler-matrix adhesion and filler dispersion. Non-AM composites made of biobased fillers are also discussed, because they can serve as a benchmark, and the lessons learned from them can be, mutatis mutandis, leveraged for developing AM composite filaments. Since extrusion-based AM lends itself to experimenting with new materials in a cost-effective way, more and better performing material combinations are expected as AM feedstocks, especially if driven by market opportunities.
