Tailoring the physical properties of poly(lactic acid) through the addition of thermoplastic polyurethane and functionalized short carbon fibers

Abstract

The elevated brittleness of commercial grades of poly(lactic acid) (PLA) may limit their use in several engineering applications. Therefore, the aim of this work is to develop a PLA-based material possessing well-balanced stiffness and toughness. Composites were prepared by blending PLA with increasing contents (from 10 to 30 wt%) of a thermoplastic polyurethane (TPU) and a fixed concentration (5 wt%) of carbon fibers (CFs), to tune the mechanical properties of the resulting materials. In order to increase the interfacial adhesion between CFs and polymeric phase, CFs were subjected to an acidic modification, by treating them in solution of H 2 SO 4 and HNO 3 . The prepared composites were characterized from a chemical, rheological, morphological, and thermomechanical point of view. Fourier transform infrared spectroscopy showed that the fiber surface reactivity was significantly enhanced by the acid treatment, with the introduction of reactive functional groups on CFs. Rheological and dynamic-mechanical tests confirmed that the introduction of acid-treated CFs implied strong fiber-matrix interactions. Thanks to the presence of the acid treated CFs, an important increase in tensile modulus and maximum stress was obtained for all the compositions. In particular, samples containing 10 wt % of TPU showed +74% tensile modulus and +43% maximum stress with respect to the unfilled blends. Moreover, the elongation at break of PLA was significantly improved (+81%) with the addition of 30 wt% of TPU. It was therefore demonstrated that the adopted approach could be effective for the preparation of novel PLA-based materials with tailorable and well-balanced properties that could find application in various technological fields.

Multifunctional epoxy/carbon composites with a fully reparable interface

“…(Venice, Italy) as a unidirectional fabric having an aerial density of 217 g/m 2 and an average fiber diameter of 7 μm. PCL (density = 1.1 g/cm 3 , molecular weight [M w ] = 80,000 g/mol) was provided by Polysciences, Inc. (Warrington, PA, USA) in the form of 3-mm pellets, and it was used as the interfacial self-healing agent. Poly(vinyl alcohol) (PVA, density = 1.2 g/cm 3 , M w = 50,000 g/mol) and polysorbate 80 (Tween ® 80) (density = 1.1 g/cm 3 , pH = 5.5-7.5, Brookfield viscosity 400-620 cps) were used as stabilizers in the preparation of PCL nanoparticles, and were both provided by Sigma Aldrich (Saint Louis, MO, USA) as a water soluble powder and a yellowish viscous liquid, respectively.…”

“…This occurs only if a good interfacial adhesion has been achieved, in order to allow an effective load transfer from the matrix to the fibers. 2,3 The interphase can be considered as an intermediate volume between the matrix and fibers, and it plays a crucial role for the mechanical properties of the composites. 4,5 This region has been often considered isotropic and homogeneous but recently, it has been discovered that it is composed by a multiphase structure with peculiar properties.…”

Synergistic toughening and reinforcement of poly(lactic acid) with epoxy‐terminated hyperbranched polymers

“…Notably, it has been demonstrated that adding substances such as poly(1,3‐propylene glycol citrate), 14 acid‐treated carbon fibers, 15 and e‐lignin 16 is a feasible approach for enhancing toughness and modifying PLA.…”