Edinburgh Napier University

  With the rapid development of wearable technology, flexible dielectric materials with environmental-friendly, low-cost and high-energy efficiency characteristics are in increasing demand. In this work, a flexible dielectric nanocomposite was developed by incorporating two components: cellulose nanofibrils (CNF) and recycled alum sludge, as the reinforcement phase and for enhancing the dielectric properties, in a bio-elastomer matrix. CNF and alum sludge were processed from waste materials which would otherwise be disposed to landfills. CNF were derived from water hyacinth, an invasive aquatic weed. Dried water hyacinth was treated using a simple and less energy-intensive process to obtain CNF. The alum sludge raw material was collected from a water treatment plant of Scottish Water and heat treated and refined before being used in preparing the composites. A biodegradable elastomer polydimethylsiloxane was used as the matrix and the nanocomposites were processed by casting the materials in petri dishes. The processed composites were characterised using scanning electron microscopy (SEM), thermogravimetric (TGA/DTG) and X-ray diffraction (XRD) analysis. The SEM micrographs illustrated CNF of approximately 20nm in diameter and alum sludge particles of approximately 200um in size. The TGA/DTG analysis results showed that a total mass of 46% has been removed when the sludge sample was heated up to 900°C. The XRD result showed that both quartz SiO2 and cubic γ-Al2O3 structures can be found in the sample that was heat treated up to 800°C. Other experiments also showed that the composites exhibit comparable mechanical and dielectric performances with other works in the literature. The work depicts that it is a sustainable practice of reusing such wastes in preparing flexible, lightweight and miniature dielectric materials that can be used for wearable technology applications.