Development and Characterization of a 3D Printed Cocoa Bean Shell Filled Recycled Polypropylene for Sustainable Composites

Abstract

Natural filler-based composites are an environmentally friendly and potentially sustainable alternative to synthetic or plastic counterparts. Recycling polymers and using agro-industrial wastes are measures that help to achieve a circular economy. Thus, this work presents the development and characterization of a 3D printing filament based on recycled polypropylene and cocoa bean shells, which has not been explored yet. The obtained composites were thermally and physically characterized. In addition, the warping effect, mechanical, and morphological analyses were performed on 3D printed specimens. Thermal analysis exhibited decreased thermal stability when cacao bean shell (CBS) particles were added due to their lignocellulosic content. A reduction in both melting enthalpy and crystallinity percentage was identified. This is caused by the increase in the amorphous structures present in the hemicellulose and lignin of the CBS. Mechanical tests showed high dependence of the mechanical properties on the 3D printing raster angle. Tensile strength increased when a raster angle of 0° was used, compared to specimens printed at 90°, due to the load direction. Tensile strength and fracture strain were improved with CBS addition in specimens printed at 90°, and better bonding between adjacent layers was achieved. Electron microscope images identified particle fracture, filler-matrix debonding, and matrix breakage as the central failure mechanisms. These failure mechanisms are attributed to the poor interfacial bonding between the CBS particles and the matrix, which reduced the tensile properties of specimens printed at 0°. On the other hand, the printing process showed that cocoa bean shell particles reduced by 67% the characteristic warping effect of recycled polypropylene during 3D printing, which is advantageous for 3D printing applications of the rPP. Thereby, potential sustainable natural filler composite filaments for 3D printing applications with low density and low cost can be developed, adding value to agro-industrial and plastic wastes.

FDM-based additive manufacturing of recycled thermoplastics and associated composites

“…CBS is hydrophilic, so it can absorb moisture from the surrounding and cause fibers to swell and generate micro-cracks in the composite. Also, the crystallinity of composite gets reduced due to the presence of amorphous hemicellulose and cellulose in CBS [ 85 ]. Likewise in another study, purified form of kraft pin lignin was reinforced in R-PLA.…”

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Fig. 13 SEM images of fractured surface of 3D printed R-PP/5% CBS tensile specimens printed at a 0° raster, b 90° raster at different magnifications [ 85 ]

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“… 2° ABS R-ABS/Fe powder (size: 50 µm) Twin screw – Not required 32.72 ± 1.5 Enhancing the thermal and mechanical properties MFI increased by 25.29% [ 81 ] 26. PP R-PP/CBS (size: 250–425 µm) Twin screw 1.75 ± 0.1 3D FF-STD Doppia 15.23 ± 0.91 Enabling the effective utilization of waste obtained from consumable products TS reduced by 41.47% [ 85 ] 27. PP R-PP/Tire microparticles Twin screw – Robot Yaskawa Motoman HP20F (modified) 6.0 Fabricating big green part with free and desired geometries Melting temperature of composite increased by 2.55% [ 84 ] …”

ABS/Silicon Dioxide Micro Particulate Composite from 3D Printing Polymeric Waste

“…Fused Filament Fabrication constructs materials by layering 3D model data on top of each other. Complex forms may be created with this 3D printing method, which reduces material waste and production time [ 35 , 36 , 37 ].…”

Processing, Characterization of Furcraea foetida (FF) Fiber and Investigation of Physical/Mechanical Properties of FF/Epoxy Composite

“…The applications of natural fiber composites are exponentially increasing in recent years as their utilization in various fields, viz., in the preparation of automotive bumpers, dashboard structures [ 10 , 11 , 12 ], ballistic armors [ 13 ], keel beam, rudder and spoiler of aircraft components, satellite launch equipment [ 14 ], scaffolds in tissue engineering, dental restorative systems [ 15 , 16 ], thermal insulation/soundproof/roofing/door/window panels and internal structures of buildings [ 17 ], packaging [ 18 ], surfboards, fishing rod, musical instrument components, artifacts and tableware, etc., [ 19 ]. Natural fibers such as rice straw [ 20 ], cocoa bean [ 21 ], agave [ 22 ], wood [ 23 ], bamboo [ 24 ], etc., are explored for 3D printing applications [ 25 ]. Additionally, the researchers are focused on developing low-cost materials by utilizing rice straw [ 26 ], rice husk [ 27 ], sugarcane bagasse [ 28 ], olive [ 29 ] and pineapple [ 30 ] leaves, peanut shell, coconut shell, coffee hull, and other agro wastes [ 31 , 32 , 33 , 34 ] for other technical applications.…”