| Abstract: | Linear low-density polyethylene (LLDPE) and polypropylene (PP) were charged by sliding under a cylindrical aluminium contact. The surface charge accumulation on the polymer films was time dependent, and a function of the sliding velocity, metal contact force, and film type. The surface potential increased linearly with velocity in the range 0.33–0.75 m/s, and showed a square-root dependence on the contact force up to 6.5 N. Thermally stimulated charge decay (TSCD) studies showed longer charge lifetimes in samples friction-charged on one side than in corona-charged samples. Friction charging creates deeper near-surface traps than are normally present in the polymers. Charge stability is further imporved by simultaneously friction charging both surfaces of the films, increasing the half-value charge decay temperature (T1/2) by 27°C and 37°C over that in corona-charged samples (i.e., to 98°C and 120°C for LLDPE and PP, respectively). These monopolarity electrets should prove useful in charge storage devices. |
