Approach in Macadamia integrifolia residue based low-density polyethylene composites on mechanical and thermal performance

Macadamia nutshell residues are generated in large quantities, around 70%-77% for each ton produced, and it is a waste material with high techno-economic potential. This work purpose a sustainable alternative to valorize macadamia nutshell residues (MN) as reinforcing in low-density polyethylene (LDPE) composites through melt mixing, using different fiber contents (0, 5, 10, and 20 wt%), and investigate the influence of fibers (residues) in composites by mechanical tests and thermal analysis. The fibers addition has significantly increased the composites' stiffness compared with neat LDPE, causing a reduction of toughness and resilience, leading to lower impact energy absorption. The LPDE/MN20% composite obtained the best tensile and flexural mechanical performance, resulting in a maximum modulus, which implies an increase of 36.9% and 77.6% compared with the neat LDPE. The addition of macadamia fibers on the composites acted as nucleation points of spherulites, which promoted an increase in the crystallization degree. Consequently, better performance of mechanical properties was observed in the green composites. Thus, the macadamia nutshell residues present a promising future as filler in LDPE for enhancing composites' thermal and mechanical properties.

Automated summary

The study demonstrates that adding macadamia nutshell residues to low-density polyethylene composites can significantly increase the material's stiffness, but it may lead to a decrease in toughness and resilience, affecting impact energy absorption. The composite with 20% macadamia nutshell residues shows the best tensile and flexural mechanical performance, while also promoting an increase in crystallinity.