Zinc Oxide (ZnO) is an inorganic compound, naturally occurring as the mineral zincite and widely produced synthetically. It is a white, powdery material known for its high chemical stability, excellent UV-blocking ability, antibacterial properties, and multifunctional industrial performance.
Zinc oxide is used in rubber manufacturing, cosmetics, pharmaceuticals, ceramics, paints, agriculture, plastics, and electronics.
Its unique combination of optical, chemical, and physical properties makes it one of the most versatile industrial chemicals.
Chemical Composition
| Component | Typical Content |
|---|---|
| Zinc Oxide (ZnO) | ≥ 99.0% – 99.9% |
| Zinc (Zn) | ~80.3% |
| Oxygen (O) | ~19.7% |
| Lead (Pb) | ≤ 0.001% |
| Cadmium (Cd) | ≤ 0.001% |
| Iron (Fe) | ≤ 0.005% |
| Loss on Ignition (LOI) | ≤ 0.5% |
Key Mechanical Properties
Zinc oxide is a ceramic-type material, so its mechanical properties differ significantly from metals.
| Property | Typical Value |
|---|---|
| Hardness (Mohs) | 4.5 |
| Compressive Strength | High (ceramic-like) |
| Tensile Strength | Low |
| Fracture Toughness | Low (brittle) |
| Elastic Modulus | ~140 GPa |
Mechanical Behavior Notes
Brittle solid (non-ductile)
High resistance to compression
Not load-bearing in bulk form
Used mainly as functional additive or filler
Physical Properties
| Property | Value |
|---|---|
| Molecular Weight | 81.38 g/mol |
| Density | 5.6 g/cm³ |
| Melting Point | ~1975°C (decomposes) |
| Boiling Point | Sublimes |
| Color | White (yellow when hot) |
| Crystal Structure | Hexagonal (Wurtzite) |
| Thermal Conductivity | ~60 W/m·K |
| Electrical Behavior | Semiconductor (n-type) |
| Refractive Index | ~2.0 |
Strengthening & Metallurgical Behavior
Crystallographic Behavior
ZnO crystallizes in the wurtzite hexagonal structure
Strong ionic-covalent bonding
High thermal and chemical stability
Strengthening Mechanisms
Zinc oxide is not metallurgically strengthened, but performance can be enhanced through:
Particle size control (nano vs micron grades)
Doping (Al, Ga, In for electronics)
Surface treatment for dispersion in polymers
Sintering in ceramics
In composites, ZnO acts as a functional reinforcement, not a structural one.
Key Characteristics
1. Excellent Chemical Stability
Resistant to water and neutral environments
Reacts with strong acids and alkalis
Stable over wide temperature ranges
2. UV Absorption & Protection
Absorbs UVA and UVB radiation
Non-photoreactive and non-toxic
Ideal for sunscreens and coatings
3. Antibacterial & Antifungal Properties
Inhibits microbial growth
Used in medical, cosmetic, and packaging applications
4. Semiconductor & Piezoelectric Properties
Used in sensors, varistors, LEDs, and electronics
Exhibits piezoelectric behavior under stress
Refining & Processing Properties
Manufacturing Methods
Indirect (French) Process
Metallic zinc vaporized and oxidized
Produces high-purity, fine particles
Direct (American) Process
Zinc ores oxidized directly
Coarser particle size
Wet Chemical Process
Ultra-pure ZnO for pharma & electronics
Processing Characteristics
Controlled particle size distribution
Excellent dispersibility in rubber & polymers
Can be surface-treated for compatibility
Available Forms
Zinc oxide is commercially available as:
White powder
Fine & micronized ZnO
Nano zinc oxide
Granules
Pellets
Dispersions & masterbatches
Pharma / cosmetic grade ZnO
Applications of Zinc Oxide
1. Rubber & Tyre Industry
Vulcanization activator
Improves elasticity and durability
Enhances heat and abrasion resistance
2. Pharmaceuticals & Cosmetics
Sunscreens
Ointments & creams
Diaper rash treatments
Skin protectants
3. Paints & Coatings
Anti-corrosive pigment
UV stabilizer
Mildew resistance
4. Ceramics & Glass
Fluxing agent
Improves glaze strength and gloss
Thermal shock resistance
5. Electronics & Energy
Varistors
Sensors
Transparent conductive films
Piezoelectric devices
6. Agriculture & Feed
Zinc nutrient source
Animal feed supplements
Fertilizers
Advantages of Zinc Oxide
✔ Multi-functional chemical compound
✔ Excellent UV and antimicrobial properties
✔ High thermal and chemical stability
✔ Compatible with multiple industries
✔ Environmentally safe and recyclable
✔ Available in multiple purity grades
Limitations
❌ Brittle material
❌ Limited solubility in water
❌ Dust control required during handling
❌ Not suitable as a structural material
Why Choose Zinc Oxide?
Zinc oxide is chosen when functional performance, safety, and versatility are essential.
Industries prefer ZnO because it:
Enhances product durability and performance
Provides UV and microbial protection
Improves rubber processing efficiency
Meets pharmaceutical and cosmetic safety standards
Offers consistent, scalable industrial performance
Zinc Oxide (ZnO) is a highly versatile inorganic compound with applications spanning rubber, healthcare, electronics, coatings, ceramics, and agriculture. While mechanically brittle, its chemical stability, semiconducting behavior, UV protection, and antimicrobial properties make it one of the most important zinc derivatives in modern industry.