In the rubber industry, heat resistance is crucial. Many rubber products are used in high-temperature settings. Examples include car parts, factory conveyor belts, and cable covers. Magnesium oxide (MgO) powder is a key additive that greatly improves rubber's ability to handle heat. This makes it essential in high-performance rubber mixes.

Magnesium Oxide Powder Chemical Stability

Magnesium oxide is very chemically stable. It has a high melting point—about 2,800°C. So it doesn’t break down easily in high heat. When rubber products are exposed to high-temperature environments, their molecular chains are prone to thermal oxidative breakdown, leading to hardening, embrittlement, or softening. As a result, the rubber loses stretch and strength. Magnesium oxide powder inhibits this process through the following mechanisms:

• MgO traps free radicals: During thermal oxidation, rubber molecules generate free radicals, triggering chain degradation reactions. MgO can capture these free radicals, slowing down the aging process of rubber.
• MgO neutralizes acids: Rubber may decompose under high temperatures to produce acidic substances, like hydrogen chloride, which can catalyze degradation reactions. As an alkaline substance, MgO neutralizes these acidic byproducts, thereby delaying rubber degradation.

For instance, adding 5-10 phr of MgO powder to engine seals helps them stay flexible and seal properly—even over long periods at 150°C or above.

rubber seals

Magnesium Oxide Powder Synergizes with Rubber

Magnesium oxide can also synergize with other components in rubber formulations to enhance the stability of the cross-linked network:

• MgO aids vulcanization: In polar rubbers such as chloroprene rubber (CR) or halogenated butyl rubber (XIIR), MgO acts as an acid acceptor. It can stop harmful byproducts (like HCl) from damaging the structure. It also helps optimize curing.
• It forms heat-resistant structures: When used with zinc oxide or stearic acid, MgO can create stronger composite structures. This improves high-temperature durability.

In cable insulation, adding magnesium oxide to certain rubbers can raise the heat resistance from 70°C to 105°C or more. That’s why it’s used in high-temperature electrical systems and electric vehicles.

magnesium oxide cables

Magnesium Oxide Facilitates Rapid Heat Dissipation

MgO has high thermal conductivity (approximately 30-60 W/m·K), which enhances the thermal management capabilities of rubber materials:

• Magnesium oxide spreads out heat: MgO particles create pathways for heat to move inside the rubber. This helps move heat away from hot spots (like from friction) to the surface where it can escape.
• Magnesium oxide reduces heat fatigue: In dynamic applications such as industrial conveyor belts or shock-absorbing components, heat buildup accelerates thermal aging of rubber. The thermal conductivity of MgO reduces operating temperatures, extending product service life.

For example, mining conveyor belts with MgO in their rubber coating show less temperature rise from friction. They keep good tear and wear resistance even when it’s hot.

Synergistic Enhancement of Other Properties

In addition to improving heat resistance, MgO offers other benefits for rubber products:

• Flame Retardancy: Magnesium oxide decomposes endothermically at high temperatures and generates a protective char layer, enhancing the material's flame retardancy.
• Optimization of Mechanical Properties: An appropriate amount of MgO can improve rubber hardness, modulus, and compression set resistance.
• Improved Processing Performance: Magnesium oxide has a certain lubricating effect, facilitating mixing and extrusion processes.

Conclusion

You’ll find magnesium oxide powder in many rubber products. These include turbocharger hoses, oil seals, high-temperature cables, industrial rollers, and heat-resistant seals. The rubber industry is always improving. New versions like nano magnesium oxide and surface-treated MgO are being developed. They disperse better and bond well with rubber. In the future, MgO will play an even more precise and versatile role in enhancing rubber’s heat resistance. Stanford Advanced Materials (SAM) offers a variety of competitively priced magnesium oxide powder products. Please Get A Quote for more information.

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Multifaceted Uses of Magnesium Oxide Powder