As an indispensable functional additive in the rubber industry, nano zinc oxide plays a pivotal role in rubber vulcanization, performance regulation, and stability enhancement due to its unique chemical properties and mechanism of action. Whether in natural rubber or synthetic rubbers (such as styrene-butadiene rubber, polybutadiene rubber, and chloroprene rubber), nano zinc oxide synergistically interacts with other additives to optimize the processing properties and end-use performance of rubber products, widely used in tires, seals, rubber hoses, and daily-use rubber goods.

The Function of Nano Zinc Oxide in the Rubber Industry

The function of nano zinc oxide in rubber systems is multifaceted. It addresses critical issues in rubber processing and application through three key dimensions: “vulcanization promotion,” “performance enhancement,” and “stability assurance.” Its mechanism of action is deeply intertwined with the chemical structure of rubber and the principles of vulcanization reactions.

1. Vulcanization Promotion: The “Core Catalyst” for Rubber Crosslinking

The vulcanization process of rubber is essentially a chemical reaction where linear polymer chains form a three-dimensional crosslinked network through vulcanizing agents (such as sulfur). Nano zinc oxide serves as an indispensable “activator” in this reaction, Its core function lies in synergizing with vulcanization accelerators (such as thiazoles and sulfonamides) to significantly enhance vulcanization efficiency, lower vulcanization temperatures, and optimize the cross-linked structure.

Nano zinc oxide reacts with vulcanization accelerators to form “reactive intermediates” (such as zinc salt complexes). These intermediates significantly reduce the activation energy required for sulfur to react with double bonds in rubber molecular chains, accelerating the formation of vulcanization bonds (C-S-C, C-S-S-C). At the same time, nano zinc oxide suppresses “side reactions” during vulcanization (such as rubber chain scission and formation of low-molecular-weight sulfides), reducing the “reversion phenomenon” in vulcanized rubber (performance degradation caused by crosslink bond breakage at elevated temperatures).

Without nano zinc oxide, rubber vulcanization requires higher temperatures (e.g., above 180°C) and longer durations (e.g., over 60 minutes), resulting in low crosslink density and poor strength in the vulcanized rubber. With the addition of nano zinc oxide, the vulcanization temperature can be reduced to 140–160°C, and the vulcanization time shortened to 10–30 minutes. Meanwhile, the cross-linked structure becomes more uniform, significantly enhancing the rubber's elasticity and resistance to compression set. For example, incorporating nano zinc oxide into tire tread compounds increases vulcanization efficiency by 30–50% and improves tread wear resistance by over 15%.

2. Performance Enhancement: Improving the mechanical strength and durability of rubber

Nano zinc oxide serves not only as a vulcanization accelerator but also as a reinforcing filler for rubber. It enhances the material's mechanical properties through both physical and chemical interactions, demonstrating particularly notable effects in improving tensile strength, tear resistance, and abrasion resistance. At the same time, it regulates the balance between rubber hardness and elasticity.

Physically, nano zinc oxide can be uniformly dispersed within the rubber matrix. Through mechanical interlocking at the “particle-rubber interface,” it disperses stress concentrations in the dispersed rubber when subjected to external forces, reducing crack initiation and propagation. Chemically, the hydroxyl groups on the nano zinc oxide surface can form chemical bonds with polar groups in the rubber molecular chains, creating a “strong interfacial bond” that further enhances the reinforcement effect.

In different rubber products, the reinforcement focus of nano zinc oxide varies. For instance, in rubber seals, nano zinc oxide can increase tensile strength from 8MPa to 12-15MPa and enhance tear strength by 20%-30%, ensuring seals remain intact under prolonged compression. In rubber conveyor belts, nano zinc oxide enhances the compound's abrasion resistance, extending the belt's service life by 20%-40% and meeting friction demands under complex operating conditions.

3. Stability Assurance: Inhibiting Rubber Aging and Degradation

Rubber products are prone to “aging phenomena” (such as hardening, brittleness, cracking, and loss of elasticity) during prolonged use due to factors like oxygen, ozone, high temperatures, and ultraviolet radiation. Nano zinc oxide can delay the rubber aging process and extend the service life of rubber products through its dual “anti-oxidation” and “anti-ozone” effects.

Nano zinc oxide reacts with free radicals generated during rubber aging, terminating chain reactions and reducing oxidative breakage of rubber molecular chains. Meanwhile, it adsorbs ozone from the air, converting it into harmless oxygen. This prevents ozone from reacting with rubber double bonds to cause ozone cracking—a condition characterized by reticular cracks on the rubber surface.

In practical applications, nano zinc oxide is often used in combination with antioxidants (such as amine-based or phenolic antioxidants). Their synergistic effect significantly enhances anti-aging performance.

From the rubber tire and rubber products to synthetic rubber, nano zinc oxide additives are playing an increasingly vital role.