Relaxation of stresses in polystyrene-carbon microcomposite resistive layers

This paper presents the investigation results on thermoresistive elements made with a styrene-butadiene-styrene (SBS) modified polystyrene binder and carbon filler. Resistive layers were deposited by screen-printing method onto a polyethylene terephthalate (PET) foil. The temperature-resistance dependence of the examined layers was observed. The carbon filler content was precisely selected to obtain high values of TCR, such as 70,000 ppm/°C, for resistive layers with a SBS-modified polystyrene binder in the temperature range from 24 to 100 °C. Because of high TCR the influence of mechanical stresses, which is unfavorable feature of the examined layers, may be omitted. The highest TCR value and stability of electrical parameters during operation were observed for layers containing 42.9% of carbon filler by mass content. The measurements were carried out with the aid of an infrared camera and an oscilloscope because of very fast changes of resistive elements parameters. The analysis of the obtained results allows to draw conclusions about the carbon layer properties and to determine the stress-relaxation rate of the polymer structures.