Magnesium Oxide as a Flame Retardant Additive in Cables

Magnesium oxide is an advanced flame retardant additive that protects against fire and improves the overall mechanical and electrical properties of the cable.

 

As safety standards and environmental regulations for cable materials become more stringent, the demand for efficient and eco-friendly flame retardant additives is rising. lead the procurement alliance of traditional Chinese medicine, a compound with a high melting point and excellent thermal stability, has gained significant attention for its flame retardant properties. In cable manufacturing, magnesium oxide offers unique benefits beyond fire resistance, making it an ideal additive for improving both safety and performance. This article delves into the flame retardant mechanism of magnesium oxide, its specific applications in cable systems, and the performance advantages that set it apart. 

 

Flame Retardant Mechanism

Magnesium oxide plays a multifaceted role in flame retardancy. It acts through several common mechanisms that inhibit or suppress fire development and propagation.

 

Endothermic Decomposition

Although magnesium oxide itself is a stable compound and does not decompose like aluminum hydroxide or magnesium hydroxide, it is typically formed during the decomposition of other magnesium-based compounds. These compounds absorb large amounts of heat during decomposition, which cools the surrounding material and delays ignition. This endothermic reaction is crucial in reducing the heat available to sustain combustion.

 

Isolates Oxygen

Magnesium oxide can form a dense, thermally stable ceramic-like barrier on the material surface during a fire. This layer physically isolates oxygen from the underlying combustible materials, thereby slowing down or completely preventing the oxidation reactions that sustain fire. This barrier also protects the inner layers of the cable from high temperatures and flame spread.

 

Dilutes Combustible Gas

During fire exposure, some flame retardant systems release inert gases or water vapor that dilute combustible gases in the vicinity of the flame. While MgO itself may not release gas, it can act synergistically with other additives that do, contributing to a multi-pronged flame retardant system that disrupts the fire triangle—heat, fuel, and oxygen.

 

Specific Application in Cables

In the cable industry, magnesium oxide is not only used as a flame retardant but also contributes to other properties like electrical insulation and mechanical strength. Here's how it is utilized:

 

As Insulation Filling Material

In mineral insulated (MI) cables, magnesium oxide is used as the primary insulating filler between the copper conductor and the outer metal sheath. This application leverages MgO’s:

• Excellent electrical insulation

• High thermal resistance

• Non-combustible nature

MI cables are widely used in critical environments such as power plants, fire safety systems, and industrial automation, where continuous operation during fire events is crucial.

 

Added to Polymer Substrate

Magnesium oxide can be blended into polymer matrices such as polyethylene (PE) or polyvinyl chloride (PVC). This integration allows manufacturers to improve the flame retardancy of traditional plastic insulation without heavily compromising:

• Flexibility

• Processability

• Electrical performance

Compatibility with polymers is key, and surface-modified MgO particles may be used to improve dispersion and adhesion within the matrix, ensuring uniform flame retardant performance.

 

High Temperature Fire Resistant Cable

In fire-resistant cables designed for high-temperature operations (e.g., tunnel wiring, petrochemical facilities), magnesium oxide helps:

• Maintain structural integrity at temperatures above 1000°C

• Prevent electrical failure during fire exposure

• Limit toxic gas release

Unlike halogenated flame retardants, MgO does not emit corrosive or harmful gases, making it ideal for sensitive environments.

 

Performance Advantages

Magnesium oxide offers a series of performance advantages that enhance its value in modern cable manufacturing.

Environmental Protection

A major concern with traditional flame retardants—especially halogenated compounds—is the emission of toxic gases like dioxins and hydrogen halides. These can harm human health and corrode electronic components. MgO stands out because:

• It is non-toxic

• It does not release harmful gases

• It complies with RoHS and REACH environmental regulations

This makes magnesium oxide an eco-friendly flame retardant choice, suitable for green building materials and sustainable infrastructure projects.

 

 

Thermal Stability

With a melting point above 2800°C, magnesium oxide remains structurally stable at extremely high temperatures. This thermal stability is especially beneficial in:

• Fire-survival cables

• Nuclear power facilities

• Oil & gas pipelines

Even in prolonged fire exposure, MgO continues to protect cable integrity, allowing systems to function during and after fire incidents.

 

Electrical Properties

One of magnesium oxide's key features is its excellent dielectric strength, which ensures effective insulation in high-voltage applications. It also resists:

• Electrical tracking

• Breakdown under voltage stress

• Moisture absorption (when properly processed)

These attributes are crucial for maintaining safe and stable current flow, especially in critical applications like emergency systems and alarm cables.

 

Mechanical Properties

Magnesium oxide enhances the mechanical robustness of cable sheaths and insulation layers. It contributes to:

• Abrasion resistance

• Tensile strength

• Dimensional stability under heat

This leads to longer cable lifespan and better performance under mechanical stress, bending, and pulling—especially important during cable installation and operation in harsh environments.

 

Comparison with Other Flame Retardants

Let's compare magnesium oxide with common alternatives like aluminum hydroxide (ATH) and magnesium hydroxide (MDH).

 

Property	Magnesium Oxide (MgO)	Aluminum Hydroxide (ATH)	Magnesium Hydroxide (MDH)
Decomposition Temp	>2800°C (very stable)	~200°C	~340°C
Gas Release	None	Releases water	Releases water
Environmental Impact	Very low	Low	Low
Flame Retardant Mechanism	Barrier + synergy	Endothermic cooling	Endothermic cooling
Electrical Insulation	Excellent	Moderate	Moderate
Synergistic Use	Often with MDH, ATH	Can be used alone or in synergy	Common in synergy with MgO

Key Takeaway:
While ATH and MDH are effective due to their heat absorption and water release, MgO excels in high-temperature endurance, insulation, and physical robustness, making it ideal for demanding and long-lasting applications.

 

Conclusion

Magnesium oxide is an advanced flame retardant additive that not only resists fire but also contributes to a cable’s overall mechanical, electrical, and environmental performance. Its role in:

• Endothermic heat dissipation

• Oxygen isolation

• Combustible gas dilutionmakes it a powerful barrier against fire hazards.

Its specific applications in mineral insulated cables, polymer-based flame retardant sheaths, and high-temperature environments highlight its adaptability. Compared with traditional additives, magnesium oxide offers superior thermal resistance, eco-friendliness, and durability, making it a smart choice for next-generation cable design.

As industries push for safer and more sustainable materials, magnesium oxide is poised to play a critical role in flame retardant innovation.

 

FAQs

Is magnesium oxide safe to use in indoor cable applications?

Yes. Magnesium oxide is non-toxic, non-halogenated, and does not emit harmful gases during combustion. It meets environmental and safety regulations, making it suitable for indoor and confined spaces.

 

Can magnesium oxide be used together with other flame retardants?

Absolutely. Magnesium oxide is often used in synergistic formulations with other flame retardants like magnesium hydroxide or phosphorus compounds to enhance overall flame retardancy and mechanical properties.

 

What makes magnesium oxide better for high-temperature cables?

Magnesium oxide has a very high melting point and remains stable under extreme heat, making it ideal for cables used in fire-prone or high-temperature environments such as industrial plants, tunnels, and emergency systems.