Preparation and characterisation of ion-conductive unsaturated polyester resins for the on-site production of resistivity sensors

Abstract

Ion-conductive unsaturated polyesters were synthesised from poly(ethylene oxide) and maleic anhydride for use in the development of improved methods for the structural health monitoring of infrastructural buildings. The unsaturated polyesters (UPs) were cross-linked with styrene using a redox initiator in the presence of LiClO4. Electrochemical impedance spectroscopy was used to study the effects of initiator and styrene concentration as well as the EO:Li+ ratio. Increasing the initiator or styrene content results in an increased resistivity of the final materials. Cross-linking with styrene does not appear to cause microphase separation into pure UP and polystyrene phases, since the resulting resistivities are significantly lower than predicted by the rule of mixtures. For all temperatures under investigation (0 to 60 °C), the lowest resistivities were found for a EO:Li+ ratio of 50 (400 Ω m at 22 °C), which is in accordance with previous findings. The electrical properties of the present materials are determined by diffusion-controlled process in such a way polarisation prevails at high temperatures. In a proof of principle experiment, one selected UP formulation was injected into drill holes in concrete and cured at different temperatures and moisture conditions. This system reliably monitors the resistivity against an embedded reference electrode.