Magnesium oxide (MgO) is categorized into various types based on its physicochemical properties and application industries. Due to its wide range of uses, even within the same industry, its effects can vary depending on the specific product. Today, we will delve into the different applications of magnesium oxide in the rubber industry.
(1) Anti-Aging Agent (Antioxidant)
Rubber molecules undergo oxidation reactions with oxygen and ozone, leading to the destruction of the rubber’s structure, reducing the mechanical properties of the products, and shortening their service life. This phenomenon is known as rubber aging. Light and heat can accelerate this oxidation process. Substances added to rubber to inhibit or slow down the aging of rubber products are called anti-aging agents (antioxidants). Antioxidants are divided into two categories: physical antioxidants and chemical antioxidants.
- Physical Antioxidants: Examples include paraffin wax, beeswax, ceresin wax, and stearic acid. These substances form a thin film on the surface of rubber products, blocking light and preventing oxygen from reacting with the rubber molecules.
- Chemical Antioxidants: Chemical antioxidants react more readily with oxygen than rubber. Adding chemical antioxidants to the rubber compound ensures that the oxygen entering the matrix reacts with the antioxidant first, reducing the contact between oxygen and rubber, effectively delaying aging. Chemical antioxidants can be classified by molecular structure into amine, aldehyde-amine, ketone-amine, phenol, and other types. Examples include Antioxidant A (N-phenyl-α-naphthylamine) and Antioxidant D (N-phenyl-β-naphthylamine).
(2) Vulcanizing Agent
Chemical agents that cause crosslinking reactions between rubber molecules are called vulcanizing agents. Adding sulfur to raw rubber, under heat, causes the linear rubber molecules to crosslink into a three-dimensional network structure, thereby improving solvent resistance, elasticity, and increasing the strength of the rubber.
This process is called vulcanization. Vulcanization is a crucial step in the rubber processing to improve the quality of rubber products. The most commonly used vulcanizing agent is sulfur. Some sulfur-containing organic compounds, metal oxides, peroxides, etc., can also be used as vulcanizing agents. These non-sulfur compounds are also known as vulcanizing agents.
(3) Vulcanization Accelerator
Vulcanization accelerators decompose into active molecules upon heating, facilitating the rapid crosslinking of sulfur and rubber molecules at lower temperatures. They shorten vulcanization time, enhance the vulcanization process, reduce sulfur usage, and help optimize the physical and mechanical properties of the rubber. Organic vulcanization accelerators include accelerators D (diphenylguanidine), TMTD (tetramethylthiuram disulfide), and DM (dibenzothiazole disulfide), while inorganic accelerators include magnesium oxide and calcium oxide. Adding Zehui’s active magnesium oxide to rubber can serve as an acid acceptor, accelerator, and anti-scorching agent to promote vulcanization and resin chelation.
(4) Softener (Plasticizer)
The main function of softeners is to ensure that various compounding ingredients are evenly dispersed in the rubber, reducing energy consumption and processing time during the mixing process. For example, softeners can enhance the tackiness of the compound before vulcanization and increase adhesion after vulcanization, which is helpful for calendaring and extrusion molding. Some softeners can impart special functions to the vulcanized rubber, such as dibutyl phthalate, which can improve the cold resistance of the rubber.
(5) Reinforcing Filler
Reinforcing fillers can improve the strength of vulcanized rubber, enhance its tear resistance, abrasion resistance, and elasticity. The most commonly used reinforcing filler is carbon black. There are more than 52 types of carbon black used in the rubber industry, making it an essential raw material. Zehui Chemical’s cable rubber-specific magnesium oxide is also an excellent choice. Cable rubber-specific magnesium oxide can improve corrosion resistance, acid resistance, high-temperature resistance, and enhance working stability under harsh conditions.
(6) Blowing Agent (Foaming Agent)
Blowing agents are essential compounding ingredients for producing microcellular rubber and sponge rubber. During the vulcanization of rubber, blowing agents decompose upon heating, releasing gases that create micro-pores inside the rubber. Common blowing agents for producing microcellular rubber include blowing agent P, blowing agent D, and blowing agent T.