Dimensional stability and mechanical properties of extruded-compression biopolymer composites made from selected Nigerian grown wood species at varying proportions

Abstract

250 µm particle size of wood and polyethylene (PE) materials were compounded at mixing proportions of 60/40, 70/30, and 80/20 (with an increase in polymer to decrease in wood content) and extruded using a single screw extruder at a temperature range of 110–135 °C. The particles of Gmelina Arborea, Tectona grandis, Cordiamilleni, and Nauclea diderichii with recycled Polyethylene were compounded and compressed at 175 N/mm to produce biopolymer composites. The biopolymer composites were subjected to dimensional stability test at 24 h of the water soak method and the ability to withstand load-bearing capacity was investigated. The outcome of the results shows that extruded-compressive biopolymer composites had values ranging from 0.06–1.43 g/cm3, 0.38–3.41%, and 0.82–6.85% for observed density, water absorption, and thickness swelling at 24 h of a water soak test. The mechanical properties values ranged from 0.28 Nmm−2–21.35 Nmm−2 and 0.44–550.06 Nmm−2 for flexural modulus and strength; and 191.43 Nmm−2–1857.24 Nmm−2 and 0.35 Nmm−2–243.75 Nmm−2 for tensile modulus and strength respectively. It was observed that moisture uptake and strength displayed by the composites vary accordingly in values obtained for wood species at different mixing proportions. As observed that the more polyethylene content is compounded to wood, the better its dimensional stability, and flexural and tensile properties. The wood particles of Cordiamilleni compounded at a proportion of 60 to 40 (polyethylene/wood) performed best in dimensional stability and load-bearing capacity. This study confirmed the effect of methods on wood species and recycled PE for manufacturing wood polymer-based composite for both indoor and outdoor applications.