Assessment of the potential application of thermoplastic polymers for insulating the electrodes of high-temperature cartridge-type electric heaters

Introduction. Tubular electric heaters are widely used in industrial and domestic heating applications. Structurally, tubular electric heaters consist of a metal shell housing a heating element, with the space between them filled with a high-temperature, heat-conducting dielectric material. A tubular electric heater is divided into several zones: the active (heating) zone, the cold zone (contact terminal zone), and the transition zone. The “cold” sections of the tubular electric heater, where the contact rods connected to the terminal wires are located, are the most critical in terms of electrical safety and durability. This zone requires reliable electrical insulation, sealing from the external environment (moisture, corrosive environments, dust, aggressive vapors), and mechanical fixation of the current-carrying elements. The aim of this study was to develop and optimize the composition of a sealing material for the cold section of a tubular electric heater. Materials and Methods. To achieve this goal, a series of pilot samples of sealing materials for protective insulating coatings were manufactured by modifying their compositional components: the polymer base, plasticizer, and filler. Samples of sealing materials for the cold section of tubular electric heaters were subjected to a comprehensive evaluation of their adhesive strength, oil-and-petrol resistance, dielectric and mechanical properties, and chemical resistance. Results. The paper presents an analysis of the feasibility of using an insulating nanomaterial for the cold section of a tubular electric heater. The results of a study of materials with various compositions, including Ammerheim Phenol Epoxy phenol-epoxy coating, T-111 epoxy resin, F-4D fluoroplastic suspension with nanoscale particles, one-component silicone sealant, ethyl cellulose, VIKSINT PK-68 organosilicon rubber, and SEDM-6 epoxy resin, showed that the most promising material for sealing the "cold" section of a tubular electric heater is F-4D fluoroplastic, which exhibits unique chemical resistance to gasoline, oils, and aggressive environments, a wide operating temperature range (from –190 to 250 °C), and excellent dielectric properties. Conclusion. Based on the results of the tests, fluoroplastic F-4D was selected as the sealing dielectric material for the “cold” section of the cartridge electric heater. This material possesses the necessary properties for operation: heat resistance, oil-and- petrol resistance, dielectric strength, high ductility, and chemical resistance. However, the fluoroplastic F-4D-based composition requires additional modification to improve adhesion to the metal surface of the tubular electric heater.