Thermomechanical and cyclic behavior of biocomposites based on renewable thermoplastics from dimer fatty acids

Microbiocomposites based on renewable thermoplastic matrices such as thermoplastic polyurethane (TPU) and polyamide (DAPA), synthesized from dimer fatty acids, and high aspect ratio talc were prepared. TPU/DAPA blends and their corresponding biocomposites exhibited mechanical behavior, which is linked to those of the matrices and their relative contents, i.e., going from a typical semicrystalline behavior (DAPA) to an elastomeric one (TPU). The understanding of the thermomechanical and cyclic behavior of these advanced materials, particularly for TPU/DAPA with high TPU content, is detailed. Addition of particles of high aspect ratio natural talc (HAR) improved the storage modulus over the whole temperature range (almost five times with 5 wt % HAR). Under cyclic manipulation, the biocomposites displayed a stress softening related to the Mullins' effect. An increase of the hysteresis and the residual deformation with the HAR content has been shown. The hyperelastic models of Mooney–Rivlin and Ogden–Dorfmann, used to predict the loading and unloading behavior, fitted with experimental data. The present work also reports the experimental characterization of the deformation mechanisms of these renewable biocomposites through different microscopic techniques at different scales, such as atomic force, scanning electron and transmission electron microscopies. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44610.