Influence of Coconut Shell Addition on Physico-Mechanical Properties of Wood Plastic Composites1

Abstract

In this study, composites with three types of thermoplastic matrix and cellulosic material in a proportion of 40% were produced. The three thermoplastic matrices were high density polyethylene (HDPE), polypropylene (PP) and low density polyethylene (LDPE), and the cellulosic materials were pure wood flour (Pinus taeda L) or a mixture of wood flour and coconut shell flour (Cocus nucifera L) in equal ratios. The objective was to evaluate the influence of addition of coconut shell on the physico-mechanical properties (density, strength and rigidity) and the distribution of the cellulosic material in the thermoplastic matrix of the manufactured composites. It was found that the composites had a satisfactory distribution of wood flour in thermoplastic matrices, but the addition of coconut shell promoted bubble formation in the resulting pieces and, thus, interfered with the material properties. The use of a coupling agent promoted interfacial adhesion (cellulose - thermoplastic matrix), which was better in high density polyethylene composites, followed by polypropylene and low density polyethylene. In general, the coconut shell addition caused a decrease of all properties compared to composites made with Loblolly Pine. In addition, the interactions between thermoplastic type and cellulosic matrix type have been statistically confirmed, which caused variations in the studied properties

Wood Pulp for Polymer Composites Production

“…The Et results found for all composites produced ranged from 707 to 2540 Mpa, higher than the pure LDPE specimens produced by Hillig et al (2017), of 232 Mpa, demonstrating an increase in stiffness with the use of any type of wood fiber in the composite. Sdrobiş et al (2012), studied bleached and unbleached pulps of Pinus sp.…”

“…Ashori and Nourbakhsh et al (2010) verify that several characteristics had a differed fiber type of the other like the extractives, granulometry, species, etc., and who had marked effects on the mechanical and physical properties of the composites. Hillig et al (2017) for injected LDPE specimens found values of 10.0 Mpa and 206 Mpa for MOR and MOE, respectively, and values of 20.3 Mpa (MOR) and of 542 Mpa (MOE) for composites with sawdust of Pinus taeda. Yang et al (2016) studying LDPE composites reinforced with vegetal peels obtained results for MOR varying between 10.5 and 19.8 Mpa when improved with one type of dye, values on average lower than those found in the composites studied here.…”

“…The MP + rLDPE (C7) and the WF + rLDPE (C8) presented characteristics like that of composites C3 and C4, respectively, since it also showed a tendency to the formation of plates, however with wrinkled surface and the formation of some fibers aggregates. Hillig et al (2017), studied composites with different particle sizes of Pinus sp. as reinforcement.…”