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Surface potential decay (SPD) of a corona charged polymeric material is a powerful tool to characterise electrical properties such as charge transport, trapping/detrapping and recombination. Over the years, various predictive simulation techniques have been proposed to describe charge transport within the material. Despite recent progress, it appears that there have been a few attempts to theoretically interpret the nature of the charge migration on the insulation surface. The aim of the present paper is to introduce a new technique with differential evolution algorithm (DEA) to reveal the steady state surface potential decay experimental results. Experimental measurement was carried on a thin film of polyethylene terephthalate (thickness: 0.5 mm; surface: 50 mm × 50 mm). The domains of variation of the factors used were respectively: 1000 V to 1800 V; 25 to 55 °C; 50 % to 80 %. The simulation results show that computational modelling and optimization approaches may improve the effectiveness to characterise electrical properties of polymers. More importantly, these studies demonstrate that DEA is effective and performs better than the experimental design method. [ABSTRACT FROM AUTHOR]

Understanding and modelling the static charge decay on an insulating material surface have been the topic of numerous research works since the nineteenth century. After an introduction on this historical context, a selection is presented here covering the various phenomena that may be held responsible for the decay: ion deposit from the surrounding atmosphere, charge injection and transport through the conduction and trapping levels of the solid, internal polarization by free carrier motion or dipole polarization, as well as surface conduction and migration of the deposited charge along the surface. Surface potential measurements are a convenient technique to study these various types of charge motion but the underlying complexity concerning their interpretation is often neglected. Depending on the context, the law of electrostatics may produce a hyperbolic as well as an exponential decay. On an insulating polymer, or any other disordered insulator, charge transport is dispersive, and conduction as well as dipolar polarization responses are described by time power laws. The knowledge of this time response is not sufficient to build a convincing physical model, because of the universality of this response, which leaves many degrees of freedom to interpret the data. Knowledge of the possible elementary processes and their signatures in the observables is therefore requested before the implementation of curve-fitting procedures. • Main processes responsible for charge decay on insulators are reviewed. • Potential decay follows usually time power laws. • Environment may influence decay process by neutralization by atmospheric ions. • Charge may drift by hopping between traps, or be screened by volume polarization. • Surface conductivity influence on potential decay in various contexts is analyzed. [ABSTRACT FROM AUTHOR]

The ability to retain localized charges at the surface or interface of dielectric materials is a universal property that applies to many different fields such as tribocharging, charge nanopatterning, nanoxerography, etc. Once the surface is charged, its stability and subsequent discharging rate will determine the potential applications of a given system. This decay rate is properly defined by the macroscopic equations which depend on dielectric constants and conductivities of the two media. Here, we derive the equations to model the decay of charge distributions localized at the surface/interface of materials and solve them avoiding additional approximations made so far. Addressing the problem in the Fourier space, we arrive to a compact generic equation which provides a useful tool to determine both the bulk and surface conductivities of a material. Furthermore, we show that Kelvin Probe Force Microscopy (KPFM) is a particularly suited method to exploit this tool. Monitoring the charge decay of previously injected charge patches on silicon dioxide (SiO 2), together with an appropriated data analysis, we verify the behavior predicted by our equations. This allows us to characterize the surface and bulk conductivities of SiO 2 layers as well as its dependence with the relative humidity. [Display omitted] • Surface charging of dielectric materials is a universal property. • The dependence of the surface charge decay rate with the system geometry is established. • Surface and bulk conductivities are obtained with Kelvin probe force microscopy. [ABSTRACT FROM AUTHOR]