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Zinc oxide is an inorganic, amphoteric metal oxide supplied primarily as a white, odorless powder; this profile covers the uncoated compound rather than a formulated dispersion or a specifically engineered nanoparticle grade.
Its principal applications include rubber vulcanization, ceramics, coatings, sunscreen formulations, skin protectants, chemical manufacture, and electronic materials.
Its technical value combines chemical reactivity with ultraviolet absorption, pigment functionality, and properties that can be controlled through particle size, surface area, and composition.
CAS Number: 1314-13-2
EC Number: 215-222-5
Molecular Formula: ZnO
Molecular Weight: 81.38 g/mol.
Synonyms: Zinc monoxide, Zinc(II) oxide, Oxozinc, ZnO, Zinc white, Chinese white, Flowers of zinc, Philosopher’s wool, Blanc de zinc, Flores de zinci, Zinci oxydum, Zincum oxydatum, Pigment White 4, C.I. Pigment White 4, C.I. 77947, Zinkoxid, Oxyde de zinc, Óxido de cinc, Zinc Oxide, ZnO, Zinc White, Chinese White, Flowers of Zinc, Zincite, Oxozinc, Zinc Monoxide, Zinc(II) Oxide, Zincous Oxide, Zinci Oxidum, Zinci Oxidum Ph. Eur., Zinci Oxidum USP, CI 77947, C.I. 77947, Pigment White 4, PW 4, CAS 1314-13-2, EC 215-222-5, Zinc Oxide Powder, Micronized Zinc Oxide, Nano Zinc Oxide, Nanoparticulate Zinc Oxide, Ultrafine Zinc Oxide, Fine Zinc Oxide, High Purity Zinc Oxide, Technical Grade Zinc Oxide, Industrial Grade Zinc Oxide, Pharmaceutical Grade Zinc Oxide, USP Grade Zinc Oxide, EP Grade Zinc Oxide, Food Grade Zinc Oxide, Cosmetic Grade Zinc Oxide, Personal Care Grade Zinc Oxide, Rubber Grade Zinc Oxide, Tire Grade Zinc Oxide, Ceramic Grade Zinc Oxide, Glass Grade Zinc Oxide, Paint Grade Zinc Oxide, Coating Grade Zinc Oxide, Pigment Grade Zinc Oxide, Feed Grade Zinc Oxide, Animal Feed Grade Zinc Oxide, Fertilizer Grade Zinc Oxide, Electronics Grade Zinc Oxide, Semiconductor Grade Zinc Oxide, Optical Grade Zinc Oxide, Reagent Grade Zinc Oxide, Laboratory Grade Zinc Oxide, Activated Zinc Oxide, Active Zinc Oxide, Surface-Treated Zinc Oxide, Coated Zinc Oxide, Hydrophobic Zinc Oxide, Hydrophilic Zinc Oxide, Transparent Zinc Oxide, UV-Blocking Zinc Oxide, UV-Absorbing Zinc Oxide, Sunscreen Grade Zinc Oxide, Topical Grade Zinc Oxide, Calamine Component Zinc Oxide, White Zinc Oxide, Synthetic Zinc Oxide, Direct Process Zinc Oxide, American Process Zinc Oxide, Indirect Process Zinc Oxide
APPLICATIONS
Rubber vulcanization
Zinc oxide activates accelerated sulfur vulcanization in rubber compounds, including formulations based on natural rubber and several synthetic elastomers.
In combination with fatty acids and organic accelerators, it participates in the formation of zinc-containing species that promote crosslink development between polymer chains.
This chemistry contributes to the mechanical strength, elasticity, and resistance to deformation required in tires, hoses, conveyor belts, seals, and footwear.
Zinc oxide performance in rubber depends on accessible surface area, dispersion, concentration, and the complete curing system.
Poor dispersion creates uneven distribution of the activator, while changes in reactivity can alter processing behavior and the resulting network.
Selecting an appropriate powder and mixing procedure therefore contributes to consistent curing and reproducible finished-part properties.
Ceramic glazes, frits, and enamels
Zinc oxide supplies a reactive oxide component to ceramic glazes, frits, and vitreous enamels.
During firing, it enters the developing glassy phase and influences melting behavior, surface appearance, and the interaction between the glaze and ceramic body.
Its contribution depends on the surrounding silica, alumina, alkali, alkaline-earth, and other oxide components rather than on zinc oxide concentration alone.
Zinc oxide can contribute to smooth glaze surfaces and can also participate in crystalline glaze development under suitable composition and firing conditions.
The balance between dissolution during heating and crystallization during cooling determines whether the finished surface remains predominantly glassy or develops visible crystalline features.
Firing atmosphere and compatibility with colorants are additional considerations because zinc-containing compositions can change the behavior of particular ceramic pigments.
Paints and protective coatings
Zinc oxide functions as a white pigment and reactive formulation ingredient in selected paints and coatings.
Its ultraviolet absorption can contribute to protection of the coating system, while interactions with the binder influence film formation and durability.
The most suitable grade depends on pigment dispersion, surface reactivity, binder chemistry, and the intended exposure conditions.
Zinc oxide can react with acidic constituents in coating binders, so its contribution extends beyond simply increasing white pigment content.
Controlled reactivity can benefit film properties, but excessive interaction may alter viscosity or storage stability.
Surface area and formulation balance are consequently important when developing a coating with predictable application and drying characteristics.
Zinc oxide also has a specialized role in certain protective can coatings, where it reacts with sulfur-containing species associated with staining.
This function differs from the sacrificial corrosion protection delivered by metallic zinc in zinc-rich primers.
Food-contact applications require a coating composition and finished article that meet the applicable requirements for their intended service.
Sunscreen formulations
Zinc oxide functions as a mineral ultraviolet filter in appropriately formulated sunscreen products.
Its optical behavior involves ultraviolet absorption together with particle-dependent scattering, allowing it to contribute to protection across UVA and UVB wavelengths.
The protection achieved by a finished sunscreen depends on concentration, dispersion, particle characteristics, film uniformity, and the complete formulation.
Zinc oxide does not have a universal sunscreen protection factor that can be assigned independently of the product containing it.
Particle engineering and surface treatment can influence visible whitening, compatibility with the vehicle, and the stability of the dispersion.
Finished products require the relevant performance testing and compliance with the rules applicable to the market in which they are supplied.
Skin protectants and topical preparations
Zinc oxide is an established ingredient in protective ointments, pastes, and creams, including preparations intended for diaper-area skin protection.
Dispersed within an appropriate base, the insoluble solid contributes to a protective layer that reduces contact between the skin and external irritants.
The vehicle, particle fineness, and solids loading influence spreadability, coverage, and the persistence of that layer.
Zinc oxide for topical preparations requires suitable purity and control of potentially harmful impurities.
A pharmaceutical or cosmetic formulation also needs appropriate physical stability so that the powder remains evenly distributed during storage and application.
The presence of zinc oxide alone does not establish the suitability of an industrial powder for direct skin application.
Sulfur removal from process gases
Zinc oxide reacts with hydrogen sulfide to form zinc sulfide and water, making it a reactive component of industrial sulfur-removal beds.
This reaction protects downstream catalysts and process equipment from sulfur contamination in suitable gas-processing and synthesis-gas systems.
Commercial absorbents are engineered into porous shapes whose composition and structure support gas contact and mechanical integrity.
Zinc oxide absorbent performance depends on temperature, gas composition, moisture, flow distribution, and the accessibility of reactive material within each particle.
A sulfur-removal bed therefore requires an application-specific operating window rather than a single temperature suitable for all zinc oxide products.
Spent absorbent contains reaction products and contaminants that require separate handling and disposal assessment.
Chemical intermediates
Zinc oxide serves as a zinc source for manufacturing salts and other zinc-containing intermediates through reactions with suitable acids.
The neutralization reaction converts the oxide into the target zinc compound while producing water, and subsequent processing determines the final concentration or solid form.
Acid selection, stoichiometry, impurity content, and separation conditions govern the composition of the resulting material.
Zinc oxide also participates in the manufacture of zinc carboxylates and other functional additives.
These derivatives can have applications in polymer processing, coatings, or lubrication that differ substantially from those of the starting oxide.
Their performance should therefore be attributed to the newly formed compound rather than automatically assigned to zinc oxide itself.
Agricultural micronutrient formulations
Zinc oxide supplies zinc to agricultural formulations intended to address an identified micronutrient requirement.
Its low water solubility makes particle size, formulation, soil conditions, and dissolution behavior important to nutrient availability.
Finely divided material can be incorporated into suitable fertilizer products, but it does not behave like a fully dissolved zinc salt.
Zinc oxide selection for agricultural use should reflect the intended delivery route and the conditions under which zinc must become available.
Soil pH and contact between particles and the surrounding medium affect dissolution and can influence the rate of nutrient release.
Application rates and crop suitability depend on the finished fertilizer, local conditions, and the relevant agronomic requirements.
DESCRIPTION
Chemical identity
Zinc oxide is a binary inorganic compound containing zinc and oxygen in a one-to-one atomic ratio.
Zinc has an oxidation state of +2, while oxygen has an oxidation state of −2.
The formula ZnO describes the composition of the solid, and the stated molecular weight represents the molar mass of one formula unit rather than a discrete molecule within the bulk crystal.
Zinc oxide must be distinguished from zinc metal, zinc hydroxide, zinc carbonate, and zinc peroxide.
These substances have different compositions, reaction behavior, and technical functions even though all contain zinc.
A formulation containing zinc oxide together with water, oils, dispersants, or surface-treatment agents likewise has properties that cannot be represented solely by those of pure ZnO.
Appearance and physical form
Zinc oxide in a purified commercial form is normally a white, odorless solid.
Powder appearance can vary with particle morphology, agglomeration, and the presence of trace impurities.
The white material becomes yellow on heating and ordinarily returns toward its original color on cooling, a characteristic that should be distinguished from permanent discoloration caused by contamination.
Zinc oxide can be supplied as a fine powder, a granulated material, or an ingredient in a prepared dispersion.
Granulation changes handling and packing behavior without necessarily changing the chemical identity of the primary particles.
A dispersion, however, includes a continuous liquid phase and may contain stabilizers, making its viscosity, solids content, and compatibility properties specific to that formulation.
Manufacture and grade differences
Zinc oxide produced by the indirect process originates from metallic zinc that is vaporized and subsequently oxidized.
The resulting oxide is collected and processed into grades with controlled physical characteristics.
Starting-material quality and production conditions influence impurity levels, particle formation, and the consistency required for different technical applications.
Zinc oxide grades sharing the same CAS number are not necessarily interchangeable in a formulation.
Differences in particle-size distribution, specific surface area, surface treatment, and agglomeration can affect wetting, reaction rate, and processing behavior.
Chemical assay alone therefore does not describe every characteristic relevant to rubber curing, pigment dispersion, or topical-product manufacture.
Solubility and amphoteric behavior
Zinc oxide is practically insoluble in water under ordinary conditions, so adding the powder to water normally produces a suspension.
Acids promote dissolution by consuming oxide and forming dissolved zinc species.
Strong alkaline solutions can also dissolve the material through zincate formation, demonstrating its amphoteric character.
Zinc oxide dissolution is influenced by pH, contact time, particle size, and the presence of substances that bind dissolved zinc.
Consequently, low solubility in plain water does not imply chemical inertness in every aqueous formulation.
A suspension containing acids or complexing ingredients can evolve differently from a simple powder-and-water mixture during storage.
Dispersion and formulation behavior
Zinc oxide is denser than the liquid phase of many formulations, making sedimentation a practical consideration.
Particle agglomeration can increase the effective settling size and interfere with uniform distribution.
Suitable wetting, dispersion, and rheology control help maintain a consistent suspension and reduce localized differences in solids concentration.
Zinc oxide surface treatments change how particles interact with oils, water, and other formulation ingredients.
A coating selected to improve compatibility with one vehicle may be unsuitable for another.
The coating chemistry and amount must therefore be considered separately from the composition of the underlying oxide.
Functional characteristics
Zinc oxide combines ultraviolet absorption with the visible-light scattering associated with dispersed particles.
The balance between these effects varies with particle dimensions, agglomeration, and the refractive properties of the surrounding medium.
This explains why a conventional white pigment powder and a specially engineered sunscreen dispersion can contain the same underlying oxide while producing different visual results.
Zinc oxide also exhibits semiconductor behavior, supporting applications in engineered electronic ceramics and related materials.
Electrical performance depends on microstructure, impurities, processing, and deliberately introduced components.
The behavior of a finished electronic component should therefore be distinguished from that of an untreated bulk powder.
PROPERTIES
Chemical nature: Inorganic amphoteric metal oxide
Appearance: White powder in purified commercial form
Odor: Odorless
Molecular formula: ZnO
Molecular weight: 81.38 g/mol
Oxidation state of zinc: +2
Physical state at room temperature: Solid
True density: Approximately 5.61 g/cm³ at 20 °C
Bulk density: Dependent on particle characteristics and packing
Water solubility: Practically insoluble
Acid solubility: Dissolves through reaction to form zinc salts
Strong-alkali behavior: Dissolves through formation of zincate species
Organic-solvent behavior: Generally insoluble in common organic solvents
pH: Applicable to a specified aqueous suspension, not to the dry solid
High-temperature behavior: Sublimation or decomposition can occur; a simple normal boiling point is not appropriate
Color on heating: Yellowing that is ordinarily reversible on cooling
Flammability: Noncombustible
Flash point: Not applicable
Vapor pressure at room temperature: Negligible
Particle size: Grade-dependent
Specific surface area: Grade-dependent
Environmental hazard: Very toxic to aquatic life with long-lasting effects.
FIRST AID
Inhalation:
Move the affected person to fresh air and allow them to rest.
Obtain medical attention for persistent coughing, fever, chest discomfort, or breathing difficulty, especially after exposure to fumes from hot processes.
Severe breathing difficulty requires emergency assistance; symptoms of metal fume fever can develop after a delay.
Skin contact:
Remove contaminated clothing and wash the affected skin with water and soap.
Seek medical advice if irritation persists.
Eye contact:
Rinse carefully with clean running water for several minutes, removing contact lenses if this can be done easily.
Continue rinsing and obtain medical attention if discomfort, redness, or visual disturbance persists.
Ingestion:
Rinse the mouth.
Do not induce vomiting, and obtain medical advice if a significant amount has been swallowed or symptoms develop.
Never give anything by mouth to an unconscious person.
Note to physicians:
Provide symptomatic and supportive treatment according to the exposure and clinical findings.
Following substantial fume inhalation, assess respiratory symptoms and the possibility of delayed metal fume fever.
HANDLING AND STORAGE
Handling:
Minimize airborne dust when opening containers, weighing material, and charging equipment.
Wear suitable work gloves, protective clothing, and eye protection where powder exposure is possible.
Use respiratory protection selected for the assessed exposure when engineering controls are insufficient.
Ventilation:
Provide extraction at powder-transfer points and equipment that releases airborne particles.
Processes generating zinc-containing fumes require effective fume capture in addition to routine room ventilation.
Assess dust and fume exposure separately because the process conditions and particle characteristics differ.
Storage:
Keep containers closed in a dry, well-ventilated location protected from contamination.
Segregate the material from acids and strong alkalis that can react with it.
Maintain packaging integrity to prevent powder loss and entry of moisture.
Spill and leak procedures:
Prevent spilled material from reaching drains, surface water, or soil.
Collect the powder carefully into closable, labeled containers using methods that minimize dust.
Arrange disposal or recovery according to the material’s contamination status and applicable waste requirements.
Handling precautions:
Avoid compressed-air cleaning and other practices that disperse powder.
Wash hands after handling and before eating or drinking.
Treat spent process material and formulated products according to their actual composition, since their hazards can differ from those of unused zinc oxide.
