Electro-responsive epoxy-polypyrrole-cotton composites with enhanced flexural strength and water resistance

Abstract Functional epoxy composites reinforced with cotton fabric layers coated with conducting polypyrrole (ppy) were prepared. Oxidative vapor phase polymerization was used to obtain thin coating of ppy. When embedded within the epoxy resin (2, 4 and 6 layers), the resulting composites showed improved flexural strength (up to 20.7 %, 26.9 % and 19.7 % for respective layers) and highly reduced water absorption (up to 61.2 %) after 24 h at 35 °C than those containing uncoated cotton layers. The conducting fabric layers allowed composites to heat upon voltage application via Joule’s effect. Statistical modelling revealed good correlation with experimental data and the influence of number of fabric layers, electrode area and applied voltage on peak temperature was studied. Composite with 6 layers showed highest peak surface temperature (92 °C) at 24 V and demonstrated a uni-directional shape recovery (greater than 60 %) when subjected to electric-heating after being deformed previously under load.