Messi Biology states that from pacifiers and mobile phone buttons to automotive seals and medical gloves, silicone gel products have already penetrated every corner of our lives. However, what many people do not know is that behind these seemingly simple silicone products lies the support of a white powder—magnesium oxide (MgO). In silicone gel formulations, magnesium oxide plays the role of an “all-rounder.” Although its dosage accounts for only 3% to 10%, it directly determines the upper performance limit of the product.
Although pure silicone gel is heat-resistant, insulating, and flexible, it is not perfect. During the vulcanization process at 150–200°C, it generates trace amounts of acidic substances such as hydrogen chloride. These “invisible killers” can quietly cleave the molecular chains of the silicone, causing the product to become brittle and crack. At the same time, pure silicone gel has relatively low tensile strength and is prone to aging and hardening when exposed to air for long periods. To solve these problems, magnesium oxide is almost an indispensable key additive.
An Acid-Scavenging Guardian: Magnesium oxide is a typical basic oxide that can rapidly neutralize the acidic substances released during the vulcanization process and physically adsorb residual acid components through its large specific surface area. This dual mechanism of “chemical neutralization and physical adsorption” not only protects the integrity of the silicone molecular chains but also prevents acid corrosion on production equipment.
A Vulcanization Booster: In the vulcanization reaction, magnesium oxide reacts with peroxide vulcanizing agents to form active intermediates, accelerating the cross-linking of silicone molecular chains and making the cross-linked structure more uniform. As a result, the vulcanization time is shortened, and the elasticity and compression set resistance of the finished product are significantly improved—which is also the secret behind why silicone buttons can withstand tens of thousands of presses and still rebound as before.
A Mechanical Reinforcement Agent: Ultra-fine magnesium oxide particles can be evenly dispersed within the silicone matrix, forming physical cross-linking points with molecular chains through surface adsorption, acting like a “steel framework” for support. With the addition of high-activity magnesium oxide, the tensile strength of silicone gel can be increased by more than 30%, making load-bearing components such as seals and conveyor belts much more durable.
An Anti-Aging Shield: Ultraviolet rays and oxygen can cause silicone to undergo free radical chain reactions, leading to hardening and cracking. Magnesium oxide can capture these free radicals while blocking UV damage to the molecular chains, significantly extending the service life of products such as outdoor architectural sealants and photovoltaic insulation sleeves.
From a tiny pacifier to aerospace seals, magnesium oxide relies on its alkalinity, adsorption capacity, and reinforcing properties to support the performance framework of silicone gel. Understanding its mechanism of action is understanding the scientific code behind the “durability” of silicone products.