LAUSR

This study aimed to present the morphological, chemical, structural, thermal, and tensile properties of three Amazonian palm fibers (Leopoldinia piassaba—PIASSAVA, Desmoncus polyacanthos—JACITARA, and Astrocaryum sp.—TUCUM) and their inner (INN) and outer (OUT) portions, in order to provide support for possible use of these fibers as reinforcement in composites. TUCUM and TUCUM OUT presented the narrower fibers and lower lumen diameters, while JACITARA INN and OUT presented the wider fibers and higher lumen diameters. PIASSAVA and TUCUM INN were the shorter fibers, while JACITARA INN and OUT were the longer. TUCUM fibers presented the higher aspect ratio, wall fraction (WF), and coefficient of rigidity (CR). PIASSAVA fibers contain relatively higher lignin and extractive contents, which led to lower crystallinity index (CI), lower tensile strength (TS), lower modulus of elasticity (E), and higher elongation at break (EB) than others. JACITARA OUT fibers presented higher CI, thermal stability, and mechanical properties than JACITARA INN. TUCUM fibers presented the higher content of cellulose, and the higher values of TS and E, as also corroborated by their higher CI and thermal stability in relation to their counterparts. TUCUM INN exhibited more interesting characteristics (such as higher CI, thermal stability, and mechanical properties) than TUCUM OUT. The experimental results in the present work contribute to the widespread use of the different portions of these underexploited Amazonian palm fibers as a source of raw materials that may be used to engineer composites and new materials for a wide range of applications.