Currently, there is no publicly available information on the internet regarding the specific value of the critical moisture content of magnesium oxide insulation in hot runner systems. This parameter is affected by many factors, including material purity, particle size, sintering process, ambient temperature and humidity, and operating conditions. There is no unified standard or publicly available measured value.
Key Factors Affecting the Hygroscopicity of Magnesium Oxide
Particle Size (Mesh Count)
Fineer particles (larger mesh count) have a larger specific surface area and are more prone to moisture absorption;
However, excessively coarse particles will affect the packing density, indirectly affecting insulation performance.
Surface Treatment Process
Magnesium oxide treated with silica forms a dense film on its surface, which can significantly reduce hygroscopicity; Special surface modification technologies (such as the Tengmei process) can effectively improve moisture resistance.
Storage and Usage Environment
Magnesium oxide stored for more than one year will develop chemical moisture absorption and needs to be dried at 500℃ for 4 hours before use; For short-term storage, it is also recommended to pre-dry at 150℃ for 1 hour to restore insulation performance.
Impurity Content
Impurities such as Fe₂O₃ can reduce the insulation resistance of heating elements and accelerate aging; High-purity MgO is more stable and suitable for high-temperature and high-humidity environments.
Protective Measures in Practical Applications
Sealed Design: The outlet of the hot runner heater must be sealed to prevent moisture from seeping into the magnesium oxide layer;
Drying Before Installation: Heating elements stored for a long time should be baked at a low temperature before use;
Avoid Contamination: Avoid contact between sweaty hands and oily substances and the magnesium oxide powder filling area during operation; In hot runner systems, magnesium oxide mainly serves as an electrical insulator and thermal conductor. Its absorption of moisture can lead to a decrease in insulation resistance, leakage, or even short circuits. Therefore, controlling ambient humidity and proper storage are crucial.
