Development of Sustainable Hierarchical Bio-composites for Industrial Applications

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Nature produces numerous hierarchical composites (e.g. wood which combines hierarchically different micro and nano-scale components with different structures and functions, Fig. 1a) with excellent mechanical performance and diverse application potential1. Design and development of such materials using waste products and renewable resources would be an important step towards a sustainable and greener world, and can greatly replace the wood-based products (reducing deforestation) and non-renewable synthetic products (reducing environmental impacts) in different industrial applications. Recent research supervised by Dr. Rana at University of Minho, Portugal showed promising results with hierarchical composites developed using commercially available microcrystalline cellulose2. Inspired by this preliminary work, this PhD project aims to develop hierarchical bio-composites (Fig. 1b) combining, in an engineered way, micro-scale renewable plant fibers, agricultural waste derived nanoscale NC and a renewable polymeric matrix. The project has the following objectives/work packages: 1) Extraction of nanocellulose from agricultural waste: NC will be extracted from agricultural waste using physical methods such as high-pressure homogenization combined with ultrasonication treatment. Different process parameters (e.g. speed/ pressure of homogenizer, ultrasonication time, temp, etc.) will be optimized to obtain NC with consistent structure, size and crystallinity and to maximize the process yield. 2) Dispersion of nanocellulose into a bio-based polymeric resin: NC will be dispersed within the bio-resin using ultrasonication process. Suspensions containing different NC wt.% and prepared at different conditions (time and temperature) will be characterized (using TEM, optical microscope, UV-Vis, etc.) for dispersion quality and stability and the best conditions will be selected for composite development.3) Nano surface engineering of plant fiber surface: As plant fibers form weak interfaces with polymers, their surface will be nano-engineered using plasma treatment to improve fiber/bio-resin matrix interface. 4) Fabrication and characterization of hierarchical composites: Hierarchical composites will be developed by impregnating plant fibers with NC dispersed resin (using compression molding) and subsequently curing them. They will be then tested for density, moisture absorption, strength and stiffness, dynamic mechanical properties, impact and fire resistance, thermal expansion and degradation, etc.5) Optimization of process parameters: At the final stage, all experimental results will be analyzed to find out the optimum set of processing conditions for maximizing performance.