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

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.

Development and Characterization of Rice Husk and Recycled Polypropylene Composite Filaments for 3D Printing.

Nowadays the use of natural fiber composites has gained significant interest due to their low density, high availability, and low cost. The present study explores the development of sustainable 3D printing filaments based on rice husk (RH), an agricultural residue, and recycled polypropylene (rPP) and the influence of fiber weight ratio on physical, thermal, mechanical, and morphological properties of 3D printing parts. Thermogravimetric analysis revealed that the composite's degradation process started earlier than for the neat rPP due to the lignocellulosic fiber components. Mechanical tests showed that tensile strength increased when using a raster angle of 0° than specimens printed at 90°, due to the weaker inter-layer bonding compared to in-layer. Furthermore, inter layer bonding tensile strength was similar for all tested materials. Scanning electron microscope (SEM) images revealed the limited interaction between the untreated fiber and matrix, which led to reduced tensile properties. However, during the printing process, composites presented lower warping than printed neat rPP. Thus, 3D printable ecofriendly natural fiber composite filaments with low density and low cost can be developed and used for 3D printing applications, contributing to reduce the impact of plastic and agricultural waste.

Importance of profile of volatile and off-odors compounds from different recycled polypropylene used for food applications.

Nowadays, polypropylene is one of the most common polymers used in the food packaging industry due to its good functionality and relatively low cost. Nevertheless, usage of plastic disposable packaging can be a generator of plastic pollution having negative environmental effects. A feasible solution for this issue would be to recycle. The polypropylene samples were submitted to two processes, forced contamination, and recycling, and they were analyzed by solid-phase microextraction gas chromatograph-olfactometry-mass spectrometry. 45 different volatile compounds were identified and 9 of them presented distinct odoriferous activities. Among them, two important markers were detected: diethyl phthalate (probably coming from the catalyst of PP polymerization, intentionally added substance (IAS)), and glycerine (a marker of non-intentionally added substances (NIAS)).

Physical-mechanical properties of wood panel composites produced with Qualea sp. sawdust and recycled polypropylene.

Adhesive-free wood-plastic composite panels made with lignocellulosic wastes, and recycled plastics can be a sustainable option for generating useful "green" products. The present work assessed the physical-mechanical properties of adhesive-free panels produced with Qualea sp. sawdust and recycled polypropylene (PP). Discarded PP packaging was used. The packages were washed and ground with a laboratory knife mill until particle size of 10 to 14 mesh. Qualea sp. sawdust was sieved to select particle size of 14 to 30 mesh. Four experimental treatments were assessed by varying the percentages of PP and sawdust, as follows, 60 and 40%, 70 and 30%, 80 and 20%, and 90 and 10%, in an entirely randomized design with 3 panels per treatment, totaling 12 panels. The mats were hot-pressed at 180 °C during 20 min, the first 10 min under pressure of 1.0 MPa and the remaining 10 min at 42 MPa. Physical-mechanical properties of the panels were obtained as follows: density, moisture content, water absorption, thickness swelling, moduli of elasticity and rupture, and Rockwell hardness. In general, an increase of the percentage of PP provided higher dimensional stability to the panels, but there was no significant influence on mechanical strength.