Design of doum palm fibers biocomposites by Reactor/elongational flow MiXer: Evaluation of morphological, mechanical, and microstructural performances

An innovative mixing device RMX (Reactor/elongational flow MiXer), based on an elongational flow, is used to formulate new biocomposites based on Doum palm fiber (at various proportions) and PLA polymer. Due to its high elongational flow, RMX has the ability to mix immiscible products and to disperse the solid phase (fiber) in the viscous phase. The morphological aspect of PLA/Palm composites shows a good appearance and high fiber orientation and dispersive efficiency as confirmed by X‐ray tomography. For higher fiber content, the porosity rate decreases from 19% for untreated biocomposites to 11% for the treated ones. An enhancement of crystallinity degree is also recorded, mainly for alkali treated PLA biocomposites. This is explained by the nucleating effect of palm fiber which could favor the germination and the growth of spherolites around reinforcements. Moreover, the tensile performances show a progressive increase in Young moduli and a decrease in tensile strength upon increasing the fibers fraction and applying alkaline treatment. We highlight an enhancement in Young moduli at about 50% and 9% for treated ones compared to PLA matrix and untreated systems respectively. These improvements are attributed to the enhancement and improvement of interfacial adhesion as confirmed by scanning electron microscopy (SEM), carried out on fractured surfaces. In addition, viscoelastic behavior was evaluated by DMA analysis and further discussed. POLYM. COMPOS., 39:E519–E530, 2018. © 2017 Society of Plastics Engineers