Mechanical Properties of Polypropylene Composites Reinforced with Macadamia Nutshell Fibers

Abstract

The use of natural fibers as an additive in polymeric matrices has attracted interest of the automotive industries, for its low cost, mechanical properties, biodegradability and lightness. However, the hydrophilic nature of the fiber makes polymer compatibility difficult. Fiber surface treatments can be used to enhance the fiber/matrix interface. In the present work, polypropylene (PP) composites reinforced with fibers from macadamia nutshell were obtained and characterized. Macadamia nutshell fibers were treated by an alkaline treatment with sodium hydroxide (NaOH 4%) to improve adhesion between fibers and matrix. Fibers were characterized by techniques of Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). The PP was mixed with the macadamia fibers (treated and untreated), in proportions of 5 and 10% (wt/wt) using a thermokinetic mixer. Furthermore tensile, flexural and impact specimens (Pure PP and composites) were prepared by an injection molding process and tested for evaluation of mechanical properties. The results showed that the insertion of treated fibers in the PP matrix increased the stiffness of the composites. However, the composites reinforced with untreated fibers presented higher impact energy absorption when compared to composites reinforced with treated fibers.

Formation and Emissions of Volatile Organic Compounds from Homo-PP and Co-PP Resins during Manufacturing Process and Accelerated Photoaging Degradation

“…PP has become the most important thermoplastic material in the automobile industry [11]. PP homopolymers, random copolymers and impact copolymers are used in products such as automotive parts and battery cases, carpeting, electrical insulation and fabrics [12]. Moreover, the application of PP in the automobile market is the largest [13].…”

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

“…It was noted clusters of sclerenchymatous fiber cells with hollow cavities that previously existed as the cell's lignin-rich inclusions, and undamaged sections of polyhedral sclereid cells joined to their neighbors via their faces. 4,30 The fiber presented some pits assigned to water and nutrients transport, 9 common in sclerenchymatous fiber cells. 4,30 The optical microscopy of MNbased LDPE composites showed spherulites increasing with the fiber loading, which is related to better phase dispersion between filler/matrix.…”

“…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 carbon‐based products, biochar, supercapacitor for powering electronic devices.…”

“…They also observed a decrease in flexural and tensile strength, followed by an increase in stiffness. Cipriano et al 9 reported the effect of macadamia nutshell chemical treatment as reinforcement in polypropylene composites (5 and 10 wt%) and noted an increase in mechanical properties.…”

“…[33][34][35][36] Thus, its use in the composites industry is an economical and environmentally viable option. Some authors have reported the MN utilization in composites as Dong et al, 5 Cipriano et al, 9 Dong et al, 31 and Cholake et al 32 Previous works do not investigate the influence of macadamia nutshell reinforced to the LDPE matrix. This work aims to investigate macadamia nutshell residues as a sustainable filler into LDPE composites, varying the MN contents from 5 to 20 wt%.…”