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Time: 2025-03-09 12:18:14 Source: Henan Province Jianyun Cable Co., Ltd.
Low-smoke halogen-free flame-retardant polyolefin insulation and sheathing materials are important safety materials in the cable industry. To improve the flame-retardant properties of these materials, magnesium hydroxide is widely used as an inorganic flame retardant. This article will introduce the flame-retardant mechanism, types, and performance characteristics of magnesium hydroxide, as well as its application in cable insulation and sheathing materials.
Magnesium hydroxide absorbs a large amount of heat by decomposing into magnesium oxide and water when heated, which reduces the surface temperature of the polymer, delays the thermal decomposition process of the polymer, and reduces its burning rate. The decomposed magnesium oxide forms a protective film that covers the surface of the flame-retardant material and acts as a barrier layer for heat and mass transfer. The generated water vapor reduces the concentration of flammable substances in the gas-phase combustion zone and cools the flammable gas.
Magnesium hydroxide on the market is mainly divided into imported chemical method, domestic chemical method and mineral method. The performance of magnesium hydroxide prepared by different methods is shown in Table 1.
| Project/Parameter | Imported chemical method | Domestic chemical method | Mineral method |
|---|---|---|---|
| Water (mass fraction)/% | 0.2 | 0.4 | 0.4 |
| Burning loss/% | 30.6 | 30.4 | 30 |
| Magnesium hydroxide (mass fraction)/% | 99 | 98 | 94 |
| Calcium oxide (mass fraction)/% | 0.1 | 0.02 | 3 |
| Bulk density/(g/mL) | 0.57 | 0.45 | 0.50 |
| Whiteness/% | 97 | 96 | 94 |
| Average particle size/μm | 1.1 | 2.5 | 3.5 |
Magnesium hydroxide can be combined with a variety of flame retardants for insulation and sheathing materials. Different types of magnesium hydroxide are suitable for different types of cable materials.
After domestic magnesium hydroxide is applied to polyolefin materials, the elongation at break and processing performance of the materials are poor. Domestic scholars have modified magnesium hydroxide by using sodium dodecylbenzene sulfonate, polyvinyl alcohol, sodium dodecyl sulfate, silane, stearic acid, oleic acid or aluminate to improve its processing performance and the elongation at break of the material.
As the main flame retardant of low-smoke halogen-free flame-retardant polyolefin insulation and sheathing materials, magnesium hydroxide can be combined with phosphorus-based, nitrogen-based, and silicon-based flame retardants to further improve the flame-retardant properties of polyolefins. With the improvement of flame-retardant requirements and the compression of product costs, the application of domestic chemical magnesium hydroxide and mineral magnesium hydroxide will be further expanded, and the modification of domestic magnesium hydroxide will become the research and development of low-smoke halogen-free flame-retardant cable materials. key of.
