The Use of Polypropylene and High-Density Polyethylene on Cork Plastic Composites for Large Scale 3D Printing

Abstract

This work focuses on studying the possibility of 3D printing of composite materials composed by cork and a polymer matrix (CPC). Initially the cork was mixed with two types of polymers (HDPE and PP) in different proportions and later processed using extrusion and injection. The composites were tested to study the physical, chemical and mechanical properties. The material was then tested on a large-scale 3D printer to study its feasibility and the ability to produce new products through 3D printing. Attention was focused on the use of pure cork, varying the concentration of cork and coupling agent in thermoplastic matrix composites of PP and HDPE. It was demonstrated that the increase of 5wt.% of coupling agent in the two types of polymers significantly improved the mechanical properties and adhesion between the phases but the increase in cork concentration decreased mechanical properties and crystallinity. The CPCs with PP showed to have better mechanical properties, better aesthetic and internal structural quality, and easier processability than those with HDPE matrix. Nevertheless, the HDPE CPCs showed a high degree of crystallization. Concerning 3D printing, it was demonstrated the possibility of making new products based on natural cork fibers, showing promising results, although additional research is still needed to optimize the process.

An Innovative Polypropylene/Waste Cork Composite Material for Spirit and Wine Stopper Caps

“…However, when a 35% load is added, the fluidity increases three-fold. This finding aligns with the observations documented by [11], when mixing 5 wt.% CoP caused a reduction of around 50% of the MFI, which was attributed to the extrusion process of the CAG. These phenomena of trend changes are characteristic of PP.…”

“…This coincides with the average particle size presented in the granulometric curve of Figure 7, where the majority of the CoP particles were measured as less than 1 mm, and they exhibited a tendency to aggregate into larger clusters ranging from 100 to 400 μm. Similarly to references [13,33], the cork cells along the axial/tangential section 75x 500x The absence of empty spaces illustrates a favorable interaction between the cork particles and the polymer matrix [11]. It is possible to distinguish how the agglomerations and the cork microstructure are rendered as hexagonal/pentagonal (honeycomb-like) or rectangular (brick wall-like) patterns, when properly aligned, as shown in the highermagnification images (the third row).…”

“…Thus, in the CoP spectrum, the band at approximately 3330 cm −1 is recognized as the stretching vibrations of O-H bonds. The distinct peaks observed in the bands at 2920 and 2853 cm −1 are indicative of the stretching vibrations of CH2 bonds within the alkyl chain of suberin [11]. The band at 1737 cm −1 is attributed to the stretching vibrations of C=O bonds present in the ester groups of suberin [32].…”

“…These particles exhibit micrometric dimensions and are evenly dispersed throughout the plastic matrix without requiring the addition of coupling agents. The absence of empty spaces illustrates a favorable interaction between the cork particles and the polymer matrix [11]. It is possible to distinguish how the agglomerations and the cork microstructure are rendered as hexagonal/pentagonal (honeycomb-like) or rectangular (brick wall-like) patterns, when properly aligned, as shown in the higher-magnification images (the third row).…”

Neutron Shielding Performance of 3D-Printed Boron Carbide PEEK Composites

“…In terms of impact strength, LDPE > LLDPE > HDPE, and in terms of mechanical properties, LDPE < LLDPE < HDPE. Thereby, HDPE has excellent physical and mechanical properties, but it is difficult to be processed in extruder owing to its long and tangled molecular chain; extremely high melt viscosity [40,41]; decomposition after heating; and extreme insensitivity to thermal shear stress, which may result in shear fracture. On the other hand, boron carbide (B 4 C) polyethylene (PE) composite has demonstrated excellent performance in shielding neutron radiation owing to the presence of high H content in polyethylene [42][43][44].…”