Zinc oxide (ZnO) is an inorganic compound, a white powder largely insoluble in water. It offers broad-spectrum protection against ultraviolet (UV) radiation, mild antiseptic qualities, a high refractive index, and acts as a binding agent with good thermal conductivity. These properties make it a valuable additive in numerous materials and products.
Natural Presence
Zinc oxide occurs naturally as the mineral zincite, though this form is relatively uncommon. Pure zincite appears as a white solid, but natural samples often contain impurities such as manganese, which can impart a yellow to reddish color. The majority of zinc oxide used today is synthetically produced, often from other zinc-containing minerals found within the Earth’s crust.
Common Consumer Products
In sunscreens, it acts as a physical blocker, reflecting and scattering harmful UVA and UVB rays. This broad-spectrum protection prevents sunburn and premature skin aging.
Diaper rash creams and topical ointments use zinc oxide to form a protective barrier on the skin. This barrier shields irritated skin from moisture and irritants, while its mild astringent and antiseptic properties help soothe inflammation and promote healing. Zinc oxide also absorbs excess moisture, contributing to a drier environment that discourages rash development.
In cosmetics, zinc oxide functions in products like foundations and powders. It acts as an opacifying agent and a pigment, contributing to coverage and color. Its UV-blocking capabilities also provide sun protection in cosmetic formulations. Calamine lotion, an anti-itch and anti-irritant formulation, includes zinc oxide for its soothing properties. Its antibacterial and deodorizing qualities also make it useful in personal care items such as deodorants and foot powders.
Industrial and Manufacturing Uses
In the rubber industry, zinc oxide is a key activator in the sulfur vulcanization process, enhancing the material’s strength, elasticity, and resistance to wear. It also functions as a reinforcing agent, improving durability, and acts as a heat and UV stabilizer to extend the lifespan of rubber products like tires and hoses. Approximately 50% to 60% of all zinc oxide produced is consumed by the rubber industry.
Zinc oxide is an ingredient in paints and coatings. It serves as a white pigment, contributing to opacity and color. It provides anti-corrosive protection and acts as an antifungal additive, preserving painted surfaces.
In ceramics and glass, zinc oxide functions as an opacifier and a fluxing agent, aiding melting processes. Its high heat capacity and low thermal expansion also improve the mechanical strength of these materials.
The electronics sector uses zinc oxide’s semiconducting and piezoelectric characteristics. It is used in varistors for surge protection and in transparent conductive films found in displays, touchscreens, and solar cells due to its high electron mobility and optical transparency. Its piezoelectric property allows it to generate electricity from mechanical stress, making it suitable for sensors that detect vibrations or pressure. It also finds use in light-emitting diodes (LEDs) and transistors.
Adhesives and sealants incorporate zinc oxide to enhance bonding strength and durability. It is included as an essential trace mineral in animal feed supplements, promoting growth, improving immune function, and supporting digestive health. Zinc oxide is also recognized as a safe food additive, used to fortify products like breakfast cereals and nutrition bars with zinc, an essential nutrient. In textiles, nanoparticles of zinc oxide provide UV protection and confer antimicrobial properties to fabrics.