Low-smoke halogen-free flame-retardant polyolefin cable compound is composed of polyolefin blend resin plus flame-retardant filler such as aluminum hydroxide, magnesium hydroxide, and some antioxidants that can improve heat resistance.
Sometimes, to reduce the amount of smoke generated during combustion, some smoke inhibitors, such as vanadium, nickel, molybdenum, iron, silicon, and nitrogen compounds are added.
Flame retardant mechanism
When burning, the flame-retardant fillers aluminum hydroxide and magnesium hydroxide will release crystal water and absorb a lot of heat. At the same time, the large amount of water vapor produced by the dehydration reaction can dilute the combustible gas, thereby preventing combustion.
Flame retardant features
Compared with halogen flame-retardant cable compounds, low-smoke halogen-free cable materials have the characteristics of flame retardancy, low smoke, halogen-free, low corrosion, and low toxicity.
Limited Oxygen Index
The oxygen index is the most commonly used combustion test in the world. For the same type of material, in most cases, the difference in flame retardancy can be relatively indicated. Therefore, the oxygen index is usually used as an assessment index of the flame retardancy of materials.
The limited oxygen index of 33-35 at room temperature can meet the flame retardant requirements of general cables, and the temperature index is about 300.
For finished cables, test the light transmittance of the cable after burning to assess the cable’s low-smoke performance. The light transmittance of the low-smoke halogen-free cable reaches more than 60% and meets the requirements.
For cable compounds, the maximum smoke density Dm during flame and flameless combustion is tested to evaluate the smoke generation performance of the material.
The smoke emmition of low-smoke halogen-free cable compounds when burned is much lower than that of halogen-containing flame-retardant cable compounds.
Applications of Fine ATH as a flame retardant in PVC Cable Compounds