Production of Natural Fiber Reinforced Polypropylene 3D Printer Filament

Recent interest in natural fiber composites is driven in part by perceived advantages related to their incorporation of renewable resources, reduced carbon footprint, and reduced toxicity in end-of-life processing. This presentation describes the process followed in a recent study in which 3D printer filament was made from polypropylene reinforced with bast fibers from industrial hemp. The process description begins with dried stems of industrial hemp and moves through decortication, pulp production, compounding, and filament production. The end result is a fiber reinforced composite filament that is compatible with 3D printers.

As is typical of fiber reinforced composites, the benefit of fiber reinforcement is best realized if the added fibers are well dispersed and have a strong interface with the matrix material; the pulp production and material compounding steps have the greatest influence on these goals. Dispersion must be specifically addressed since hemp bast fibers in the decorticated state are bundled together by non-fiber components; the pulping process is intended to remove the non-fiber components and facilitate fiber separation. Interfacial bonding between polypropylene (hydrophobic) and hemp fibers (hydrophilic) is naturally weak. Enhancement of interfacial strength can be achieved through introduction of a coupling agent which is capable of forming stronger bonds with each constituent thus forming a bridge. The compounding process provides opportunity to add a coupling agent.

This presentation will include a review of the process and the equipment used to produce hemp fiber reinforced polypropylene filament. Images of the material at different stages of the process will provide additional context.