High elongation requirement: How to improve the fracture elongation of magnesium hydroxide cables
In recent years, with the increasingly strict environmental regulations, traditional halogen containing flame-retardant cables have gradually been replaced by halogen-free flame-retardant materials. Magnesium hydroxide has become an ideal choice for the new generation of environmentally friendly cable filling or sheath materials due to its excellent flame retardancy, low smoke and non-toxic characteristics. However, in practical applications, magnesium hydroxide cables commonly suffer from low elongation at break, which can lead to cracking, brittle fracture, and other phenomena during installation or operation, affecting their overall performance.
Therefore, how to effectively improve the elongation at break of magnesium hydroxide cables while ensuring flame retardancy has become one of the urgent technical challenges in the current cable industry.
To understand why magnesium hydroxide cables have insufficient elongation, it is first necessary to understand their material properties and structural composition. Magnesium hydroxide is a highly rigid inorganic filler that does not have ductility and has poor dispersibility in polymer matrices, which can easily form stress concentration points and reduce the flexibility and elongation at break of the material.
In addition, the higher the proportion of magnesium hydroxide added, although the flame retardant effect is more obvious, the negative impact on the mechanical properties of cable materials is also greater. Therefore, how to maintain the flexibility and processing performance of the material under high filling content is the key to improving the elongation at break of magnesium hydroxide cables.
The core of improving the elongation at break lies in enhancing the compatibility and dispersibility of magnesium hydroxide in polymer substrates. At present, the industry mainly achieves this goal through the following ways:
Firstly, surface modification treatment. By organic treatment of magnesium hydroxide particles, such as using silane coupling agents, titanate coupling agents, or fatty acid surfactants, the interfacial adhesion between them and polymers can be significantly improved, reducing stress concentration caused by interfacial separation and thus enhancing the elongation performance of the material.
Next is to choose a suitable polymer substrate. Different resin systems have varying degrees of tolerance for magnesium hydroxide. For example, flexible resins such as ethylene vinyl acetate copolymer (EVA), polyolefin elastomer (POE), and thermoplastic polyurethane (TPU) are more suitable for the mechanical performance requirements under high filling levels compared to traditional polyethylene (PE) or polypropylene (PP). Reasonable selection of substrates can help achieve higher elongation at break without sacrificing flame retardancy.
The third is to optimize formula design and processing technology. By introducing plasticizers, compatibilizers, or elastomer components, the rigidity enhancement effect caused by magnesium hydroxide can be alleviated to some extent. Meanwhile, controlling parameters such as temperature and shear rate during the extrusion molding process can also help improve the uniformity of the internal structure of the material, thereby enhancing its elongation performance.
In addition, in recent years, some new nanoscale magnesium hydroxide materials have also begun to enter the market. This type of material has smaller particle size and larger specific surface area, which can provide better mechanical properties and processing flowability under the same filling amount, providing a new technological path for improving fracture elongation.
In practical engineering applications, many enterprises have achieved good results through the above methods. For example, some cable manufacturers use surface treated high-purity magnesium hydroxide and POE elastomer as the substrate when producing high-voltage cables for new energy vehicles, successfully increasing the cable's elongation at break to over 150% while still maintaining good flame retardancy and temperature stability.
Some companies are also trying to add small amounts of high-performance additives such as graphene or carbon nanotubes during the research and development stage to further improve the flexibility and thermal conductivity of the materials. These cutting-edge explorations, although not yet commercialized on a large scale, have shown tremendous potential for development.
Faced with the challenge of high elongation demand, the performance improvement of magnesium hydroxide cables is not out of reach. Through scientific material modification, rational formula design, and refined production process optimization, it is entirely possible to achieve a dual breakthrough in cable flexibility and durability while balancing flame retardancy and environmental friendliness. This undoubtedly has important practical significance for promoting the green transformation and technological upgrading of China's cable industry.