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

Abstract

Macadamia nutshell residues are generated in large quantities, around 70%-77% for each ton produced, and it is a waste material with high technoeconomic 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. K E Y W O R D S biopolymers, mechanical properties, renewable polymers, thermal properties, thermoplastics 1 | INTRODUCTION Nutshells are often utilized in a relatively low-value application, such as, composts, mulches, fertilizers, and animal feed. 1 The unit operations involved in the separation of nut kernel from other nut parts can vary depending on the nut type. Still, there are common steps, such as, drying, extraction of the components, shelling, and separation process, giving the nut kernels and dry nutshell. 2 The agroindustrial crop's valorization is interesting for synthetic chemistry, perfumery, cosmetics, biomedicine, and energy industries. Some studies reported techno-economic valorization of nutshells residues, such as, macadamia, 3-9 pistachio, 10,11 pecan, 12-17 almond, 18 cashew, 19-21 cedar, 22 oak, 23 fox 24 for catalytic pyrolysis, wastewater treatment, bio-fillers in a polymeric matrix, microporous sorbents, preparation of carbonbased products, biochar, supercapacitor for powering electronic devices. Among the agroindustrial nutshell waste, macadamia nutshells are highlighted. Around 44,000 metric tons (kernel) are produced worldwide, 25,26 which generates

Comparison of the usage of nut shell, walnut shell, and pistachio shell as a reinforcement particle on the mechanical and wear performance of polypropylene

“…The strong particle–matrix interface is self‐formed without the use of any interfacing agents, which has a positive effect on the tensile strength. The increase in tensile strength with particle reinforcement can be explained by the good matrix‐reinforcement interface adhesion, and the load on the matrix can be transferred to the reinforcement 3,10,11,13,21,22 . However, the agglomeration that occurs with increasing amounts of reinforcement particles possibly has this positive effect to decrease.…”

“…The increase in tensile strength with particle reinforcement can be explained by the good matrix-reinforcement interface adhesion, and the load on the matrix can be transferred to the reinforcement. 3,10,11,13,21,22 However, the agglomeration that occurs with increasing amounts of reinforcement particles possibly has this positive effect to decrease. As expected, the modulus of elasticity increased with the rigid particle reinforcement, and the material, which is reinforced at the rate of 1 wt% became most rigid (has a highest modulus) compared with neat PP.…”

“…Owing to the properties of these biobased fillers, for example, eco-friendliness, low density, low cost, and so forth, they replace the universal fillers. [5][6][7][8][9][10][11][12][13][14] Table 1 summarizes previous studies on dried fruit shells used as filler materials in polymer matrices. There is no common study on the wear resistance of dried fruit shell-filled composite samples.…”

“…Recently, ecofriendly biodegradable fibers and/or particles have been growingly used as reinforcement materials for composites. Owing to the properties of these biobased fillers, for example, eco‐friendliness, low density, low cost, and so forth, they replace the universal fillers 5–14 …”

Exploring the Prospects of Macadamia Nutshells for Bio-Synthetic Polymer Composites: A Review

“…As a botanical structure, macadamia nutshells are delicately optimized, exhibiting exceptional strength and toughness resulting from ecological evolution and natural selection. These nutshells possess a cellular solid mass with relatively high strength and low density; however, their structure differs considerably from that of trees, displaying isotropic and uniform characteristics [7]. Macadamia nutshell-filled polymeric composites hold promising potential for manufacturing various structural components, including sandwich composites, with prospective applications in infrastructure, aerospace, and automotive industries.…”