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Natural fibre-based composites have been investigated as a viable ecological alternative to conventional materials, combining low-cost and sustainable features to engineering products. In tropical countries, such as Brazil, there are many lignocellulosic residues that are discarded in nature, polluting the environment, such as the Tucuma fruit, which generates about 50 tonnes/month of solid waste only in the city of Manaus (State of Amazonas). This work investigates a novel wood-plastic composite (WPC) made from recycled polypropylene (PP) and Tucuma endocarp powder (TEP) without coupling agents that encompasses social and environmental issues. WPCs are composed of 10, 20, 30, 40 and 50 wt% of TEP combined with PP by injection moulding, being characterised by SEM, FTIR, flammability, water absorption, ageing, tensile, compressive, three-point bending, impact and scratch tests. TEP does not react to the matrix phase, presenting 49.4 % and 37.4 % of cellulose and lignin, respectively. In general, the incorporation of TEP not only increases the elastic modulus and the dynamic friction coefficient, but also reduces the strength and the burning rate of WPCs. WPC preserves its physical integrity after ageing, absorbing up to 1.6 % of water. Composites made with 20 wt% of TEP can be considered promising materials to be used as wood plastic for sustainable engineering applications.

This work investigates a hybrid polyester composite consisted of Curaua natural fibres and organophilic clay nanoparticles. A Taguchi method is used to identify the effects of fibre fraction (10, 20 and 30 wt%), alkaline treatment concentration (NaOH, 2.5, 5 and 10 wt%), treatment time (2, 4 and 8 h) and nanoparticle content (2.5, 5 and 10 wt%) on the mechanical behaviour of the hybrid composites under tension and three-point bending. X-ray, FTIR and microstructural analysis are performed to assess the treated and untreated fibre surfaces. The optimum combination of the process parameters for the tensile and flexural properties is: fibre content at 30 wt%, NaOH concentration at 5 wt%, treatment time at 8 h and nanoclay inclusions at 5 wt%. A mean tensile and flexural strength of 36.13 MPa and 32.55 MPa are obtained, which represents percent increases of 39.22 % and 25.43 % compared to the polyester polymer in pristine condition.