Heat as a Conductivity Factor of Electrically Conductive Yarns Woven into Fabric

Abstract

In recent years, more and more researchers have been focused on electrically conductive textiles that generate heat or transmit electrical signals and energy to embedded electrical components. In this paper, the dissipation of heat due to the flow of electric current at given voltages is investigated, and at the same time it is determined how this heat affects the change in the electrical resistance of the electrically conductive yarn in the immediate surroundings. Three fabric samples were woven in a plain weave with three types of different electrically conductive yarns. Three electrically conductive yarns are woven in parallel in the weft direction and separated from each other by one polyester (PES) yarn due to electrical insulaton. Conductive yarns are electrically connected so that the outer yarns are used for heating by the flow of electric current at a certain constant voltage, and the central yarn is used only to measure changes in electrical resistance. When electrothermally conductive fabrics are subjected to certain voltages over time, experimental results have shown that resistance values increase over a short period of time and then gradually decrease, while the temperature gradually increases and stabilizes over time. Based on the analysis of the obtained results of the ratio between the values of applied voltage and temperature to the electrically conductive yarns, the value of thermal dissipation in conductive yarns can be calculated in advance depending on the applied voltage. Furthermore, the obtained results can be further used in applications where conductive yarns are used as heaters for realistic prediction of the obtained heat.

Keywords: electrically conductive yarn resistance; heat; plain weave; temperature; woven fabric.

Figure 1

Plain weave: (a) woven fabric structure; (b) macro photo.

Figure 2

Schematic presentation of connecting sample and measuring system: 1—regulated power supply unit; 2—specimen of fabric; 3—conductive yarns; 4—resistance measuring circuit; 5—IR temperature sensors (MLX90614); 6—microcontroller for powering and acquisition temperature data; 7—NIDAQ converter; 8—personal computer for time control and data acquisition.

Figure 3

Temperature movement of the electrically conductive part of the sample at certain voltages: (a) sample 1; (b) sample 2; (c) sample 3.

Figure 4

Change in the electrical resistance of the electrically conductive yarn of sample 1 under the influence of temperature change at given voltages.

Figure 5

Change in resistance of the electrically conductive yarn of sample 2 under the influence of heat at given voltages.

Figure 6

Change in the electrical resistance of the electrically conductive yarn of sample 3 under the influence of heat by heating at given voltage values.

Figure 7

Change in the electrical resistance of the electrically conductive yarn with increasing temperatures at certain voltage values: (a) sample 1; (b) sample 2; (c) sample 3. In the continuation of the presentation of the results, diagrams of the change in resistance depending on the increase in the temperature of the conductive yarn are given.

Figure 8

Temperature measurement results at selected voltage values: (a) sample 1; (b) sample 2; (c) sample 3.

Figure 9

Comparison of three resistance values (start, average, end) at given voltage values in sample 1.

Figure 10

Comparison of three resistance values (start, average, end) at given voltage values in sample 2.

Figure 11

Comparison of three resistance values (start, average, and end) at given voltage values in sample 3.

Figure 12

Dependence of electrical resistance R of electrically conductive yarns on supply voltage U: (a) Sample 1; (b) Sample 2; (c) Sample 3.

Figure 13

Dependence of equilibrium temperature T_e of electrically conductive yarns on supply voltage U: (a) sample 1; (b) sample 2; (c) sample 3.