In the industrial heating system composed of cartridge heaters and molds, thermal conductive media is often regarded as a minor auxiliary material, but its performance directly determines the heat transfer efficiency and service life of cartridge heaters. Many manufacturers invest a lot of costs in selecting high-performance cartridge heaters, but ignore the selection and use of thermal conductive media, resulting in failure to exert the due performance of heaters, frequent failures and increased operating costs. Based on practical application experience, the matching of thermal conductive media and cartridge heaters is a key link that cannot be ignored in optimizing heating effect.
Thermal conductive media mainly fill the micro gap between the outer wall of the cartridge heater and the inner wall of the mold installation hole, eliminating the air layer with extremely low thermal conductivity. Air is a natural thermal barrier, even a tiny air gap will hinder the heat generated by the heater from being quickly transferred to the mold, leading to heat accumulation inside the heater, rising surface temperature, accelerated aging of internal insulation materials and resistance wires, and ultimately shortening the service life. High-quality thermal conductive media can reduce the thermal resistance between contact surfaces by more than 60%, improve heat transfer efficiency, and ensure that the heat of the heater is evenly conducted to the mold.
The selection of thermal conductive media needs to be matched with the operating temperature of the cartridge heater. For conventional plastic injection molds with operating temperature below 300℃, ordinary silicone-based thermal conductive paste is sufficient to meet the demand, which has good adhesion and thermal conductivity, and is easy to apply and clean. For molds with operating temperature between 300℃ and 600℃, high-temperature resistant ceramic-based thermal conductive paste should be selected, which will not volatilize, carbonize or dry out at high temperature, maintaining stable thermal conductivity. In ultra-high temperature environments above 600℃, thermal conductive graphite sheets or metal thermal conductive gaskets are more suitable, with excellent high-temperature stability and thermal conductivity, avoiding failure of paste media at extreme temperatures.
The use method of thermal conductive media also directly affects the performance. When applying thermal conductive paste, it should be evenly coated on the entire effective heating surface of the cartridge heater, with a thickness controlled between 0.05mm and 0.1mm. Excessive coating will not improve the thermal conductivity effect, but will cause waste and pollution of surrounding components; too thin coating cannot completely fill the micro gap, failing to achieve the expected heat transfer effect. For thermal conductive graphite sheets, they need to be cut to fit the size of the heater, ensuring complete fitting between the sheet and the heater, mold hole wall, without wrinkles or gaps.
In the daily maintenance process, the replacement of thermal conductive media is also crucial. After long-term use at high temperature, thermal conductive media will gradually age, dry, or mix with impurities, resulting in reduced thermal conductivity. When replacing or maintaining the cartridge heater, the old thermal conductive media on the heater surface and mold hole wall should be completely cleaned, and then new media should be reapplied. In addition, for molds in vibration environments, thermal conductive media with good anti-seismic and anti-shedding properties should be selected to prevent the media from falling off due to vibration and losing thermal conductivity.
It is also necessary to pay attention to the compatibility between thermal conductive media and cartridge heater sheath materials. Some corrosive thermal conductive media will react with stainless steel or alloy sheaths, causing corrosion damage to the heater. Before use, compatibility tests should be carried out to ensure that the media will not cause corrosion to the heater and mold materials. Choosing high-quality, matching thermal conductive media and standardizing its use can maximize the performance of cartridge heaters, reduce energy consumption, and extend the service cycle of heating components.
