Nanoparticle Modification of Natural Fibers for Structural Composites

Abstract

Natural fibers are a lightweight, carbon negative alternative to synthetic reinforcing agents in polymer composites. However, natural fibers typically exhibit lower mechanical performance than glass fibers due to weak interfacial adhesion between plant cells in the fiber and damage to the fibers during extraction from a plant stem. However, improvement of natural fiber mechanical performance could enable their wide-scale incorporation in structural composite applications, significantly reducing composite weight and carbon footprint. This study seeks to develop a novel, cost-effective method to significantly improve natural fiber stiffness via repair of damage caused by extraction and/ or stiffening of the weak cellular interfaces within a natural fiber. Supercritical fluids have been shown to be capable of swelling and plasticizing amorphous polymers, increasing additive absorption. In this work. supercritical-carbon dioxide (scCO2) was used as a solvent to assist with infusion of nanoparticles into flax fibers at pressures ranging from 1200-4000psi. Fiber analysis with Plasma Focused Ion Beam-Scanning Electron Microscopy (PFIB-SEM) showed that nanoparticles were capable of penetrating and bridging openings between cells, suggesting the ability for nanoparticle treatment to assist with crack repair. Additionally, treated fibers contained uniform surface coatings of nanoparticles, potentially reducing fiber porosity and modifying interfacial properties when embedded in a polymer matrix. Overall, this method of nanoparticle reinforcement of natural fibers could enable development of high-performance lightweight, low-carbon footprint composites for transportation or industrial applications.