Pyroresistive Properties of Composites Based on HDPE and Carbon Fillers

Abstract

Electrothermal processes were studied in pyroresistive composites based on high-density polyethylene (HDPE) containing 8 vol.% carbon black (CB), 8 vol.% carbon fibers (CF), and their mixture 4 vol.% CB + 4 vol.% CF. It is shown that the kinetic heating curves of composites are well described by an exponential dependence with a certain heating rate constant k for each type of composite. After a short heating time, the equilibrium temperature Te is reached in the sample. When the applied voltage exceeds a certain value, the Te value decreases due to the presence of the positive temperature coefficient of resistance (PTC) effect. Due to the PTC effect, the composites exhibit a self-regulating effect relative to the Te. Relations between the applied voltage, electric power, and equilibrium temperature are found, the Te value depends on the applied voltage according to the quadratic law whereas there is a linear relationship between the Te and electric power. A possible application of such pyroresistive composites is resistance welding of plastics using a heating element (HE) made of a pyroresistive material. The use of HDPE-CB composite to create HE for resistance welding is demonstrated and the welded joint of HDPE parts obtained using HE is shown.

Heating Elements based on PVC and Carbon Fillers

“…51 Figure 4J,K shows the dependence of the equilibrium temperature T e on the applied voltage U for the studied composites. As shown in a previous work, 30 this dependence is described by the quadratic equation…”

“…A comparison of the parameters of PVC-based composites with HDPE-based composites containing the same fillers (CB, CF, and CB/CF) and having the same sample geometry 30 demonstrates similar values of the pyroresistive parameters given in Table 2. The greatest existing differences between HDPE and PVC-based composites are in the conditions for achieving the equilibrium temperature.…”

“…temperature T e achieved. As can be seen, it is described by a linear dependence 30 = + • T T b P e 0 (11) over the entire temperature and power range, regardless of the manifestation of the PTC effect. Coefficient b can be calculated from the slope of the linear relationship T e ∼ P and indicates the efficiency of heating the composite by Joule heat.…”

“…For studies of pyroresistive properties, samples were cut from the disks in the form of a strip 15 mm wide. The sample preparation scheme is given in detail in ref 30.…”

Investigation of Cyclic Stability and Pyro-Resistive Properties in High-Density Polyethylene/Tungsten Carbide Composites Under Thermal and Electric Activation

“…This demonstrated promising potential for application as an electric heating coating for anti-icing/defrosting purposes. Mamunya et al 35 studied the electrical heating process of carbon fiber/CB/ HDPE composite materials with varying carbon fiber content. When the voltage exceeds a certain threshold, the increased resistance, due to the PTC effect, reduces the electrical power of Joule heating, thereby maintaining the heating temperature at the level associated with that power.…”