Mechanical Recycling of Low-Density Polyethylene/Carbon Nanotube Composites and Its Effect on Material Properties

Abstract

In this paper, the impact of recycling and remanufacturing on the behavior of low-density polyethylene/multi-walled carbon nanotube (LDPE/MWCNT) composites is investigated. LDPE/MWCNT composites with 0.1–5 wt%, previously manufactured by injection molding, were mechanically recycled and remanufactured by injection molding and 3D filament extrusion, and the rheological, electrical, and mechanical properties were analyzed and compared with those of virgin composites under the same conditions. Experimental results demonstrate that the recycled LDPE/MWCNT composites have similar rheological, electrical, and mechanical properties as that of virgin composites, if not better. Therefore, the recycled LDPE/MWCNT composites have a great potential for being used in engineering applications, while reducing the environmental impact.

Mechanical Recycling of Ethylene-Vinyl Acetate/Carbon Nanotube Nanocomposites: Processing, Thermal, Rheological, Mechanical and Electrical Behavior

“…The main effect plot in Figure 14 and ANOVA (see Tables S2–S5 of Supplementary Materials ) show that the reprocessing has a decreasing effect on Young’s modulus, tensile strength and stress at a break of about 25.6%, 13.5%, respectively 12.9% compared to the virgin EVA/MWCNT. Similar behavior has been previously reported for recycled polymer/CNT nanocomposites [ 31 , 32 , 79 ]. The decrease in the mechanical properties with reprocessing cycle, except for the strain at the break that increased by about 6.5%, may be associated with thermal and mechanical degradation of the polymer matrix due to multiple exposures to high temperatures and high shear rates during the injection molding process.…”

“…The presence of MWCNTs affects the MFI of nanocomposites through chain mobility. The addition of MWCNTs blocks the movement of the polymer chains during flow, resulting in a significant increase in the flow resistance [ 31 , 32 ].…”

“…In this study, the flow activation energy was obtained based on the Arrhenius equation [ 9 , 32 , 75 ] where is the apparent shear viscosity (Pa·s), A is a constant, is the flow activation energy (kJ/mol), R is gas constant ( R = 8.314 J mol −1 K −1 ), and T is the absolute temperature (K).…”

“…However, it was found that the stress and strain at break increased after reprocessing, indicating the reduction of CNT aggregates during mechanical reprocessing. Stan et al [ 32 ] studied the impact of mechanical recycling and remanufacturing by injection molding on the behavior of LDPE nanocomposites with 0.1–5 wt.% of CNTs. After the first recycling process, it was found that the mechanical, electrical and rheological properties of the recycled nanocomposites were similar to those of the virgin nanocomposites.…”

“…From the literature review [ 25 , 26 , 30 , 31 , 32 ], it can be concluded that knowledge of the process-induced degradation of the physical, mechanical and thermal properties of polymer/CNT nanocomposites due to recycling operations (grinding and melt reprocessing) is of paramount importance in order to understand the role of CNTs during the recycling process and to consider the use of the recycled nanocomposites for industrial applications.…”