The Investigation of Electret Film Durability in Polyethylene Terephthalate (PET) from a Certain Angle of their Application as Pressure Sensors

Abstract

Article presents research methods and their results for 100μm polyethylene terephthalate PET film, from a certain angle of its application as pressure sensors. Film was polarized at 150V/μm electric field intensity in dwo different temperatures: 60°C and 90°C. Direction of polarization was measured by thermally stimulated depolarization current TSDC. Results shows presence of homo-and heterocharge. Relaxation was calculated by two methods: from relationship ln J (T) = const – W/kT and from relationship (T) = P (T) / J (T). Activation energy for heterocharge calculated by first relationship is 6.14 eV to 6.77 eV and its relaxation time in 24°C is ~1020 years. For second one relationship, relaxation time in 24°C is ~1035 years. Piezoelectric voltage in 33 direction is 74V for termination resistance 1014Ω and 30V for termination resistance 109Ωfor applied stress 10N/cm2 from 10 cm2 surface. Obtained results for studied PET film, encourage to use it in practice as pressure sensors.

Electronic measurement system of foot plantar pressure

“…During selection of the material for the pressure sensors, the authors focused on permanently polarized polymer films: polyethylene -polypropylene (PE -PP) (Klimiec et al, 2008), polypropylene (PP) (Klimiec et al, 2010), polyethylene tereftalate (PET) (Klimiec et al, 2011a) and PVDF (Klimiec et al, 2011b). The main factor considered during the selection is good springiness in the required range of the pressure, because short time of recovery after removing the force, is a very important factor for sensor stability.…”