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Send EmailZinc Oxide, Pigment White 4, Zinc Oxide Gold Seal, Zinc Oxide White Seal, 1314-13-2
ZINC OXIDE (ZnO)
1. Chemical Identity
| Property | Value |
|---|---|
| Molecular Formula | ZnO |
| CAS Number | 1314-13-2 |
| EC Number | 215-222-5 |
| Molecular Weight | 81.38 g/mol |
| Synonyms | Pigment White 4, Zinc White, Zinc Oxide, Activox, Gold Seal, White Seal, Florescent White |
2. Physicochemical Properties
| Parameter | Value |
|---|---|
| Appearance | White, fine, odorless powder |
| Melting Point | 1975 °C (sublimes) |
| Density | 5.68 g/cm³ (20°C) |
| Solubility in Water | Very low (1.2 – 2.9 mg/L) |
| pH (10% suspension) | 7 – 8 (neutral) |
| Particle Size | Micro: 0.5–5 µm / Nano: 20–100 nm |
| BET Surface Area | Micro: 1–5 m²/g / Nano: 10–50 m²/g |
| Refractive Index | 2.01 (high opacity) |
| Dielectric Constant | ~8.5 |
3. Typical Specifications (Common Limits)
| Parameter | Limit / Value |
|---|---|
| Purity (ZnO) | ≥99.0% – 99.9% (grade dependent) |
| Pb (Lead) | ≤10 – 20 ppm |
| Cd (Cadmium) | ≤5 – 10 ppm |
| As (Arsenic) | ≤3 – 5 ppm |
| Hg (Mercury) | ≤1 ppm |
| Loss on Drying | ≤0.5% |
| Acid Insoluble | ≤0.02% |
| Coating Type (optional) | Silica, stearic acid, simethicone |
4. Grade Comparison Table (Purity / Suitability)
| Grade / Type | Purity (%) | Surface Area (m²/g) | Suitable Sectors | Status | Critical Notes |
|---|---|---|---|---|---|
| Low Grade / Technical | 50-70 | 1-2 | General industrial filler, low-cost pigment | Limited | Not suitable for cosmetics/pharma |
| Agricultural Grade | 70-85 | 2-4 | Fertilizers, foliar sprays, soil amendments | Suitable | Zn micronutrient source |
| Feed Grade (Low Purity) | 80-90 | 2-5 | Animal feed premixes | Suitable | Heavy metals (Pb, Cd) strictly controlled |
| Industrial Standard (White Seal) | ≥99.0 | 3-6 | Rubber vulcanization, plastics, paints, ceramics | Suitable | Most common industrial grade |
| High Purity (Gold Seal) | ≥99.5 | 4-10 | Cosmetics, pharmaceuticals, advanced ceramics | Suitable | GMP/cosmetic compliant |
| Pharma/Cosmetic Grade | ≥99.7 – 99.9 | 5-12 | Ointments, sunscreens, baby powders | Suitable | USP, EU 1223/2009 compliant |
| Nano Grade (coated/uncoated) | ≥99.5 | 15-50 | Transparent sunscreens, antimicrobial coatings, electronics | Suitable | “nano” labeling + safety file required |
Note: Coated forms (silica, stearate) improve dispersion and reduce photocatalytic activity – preferred for stable formulations.
5. Applications & Typical Usage Levels (by Sector)
| Sector / Application | Compatibility | Typical Usage Level | Technical Notes |
|---|---|---|---|
| Sunscreens (SPF) | ✅ | 5–25% | Nano/coated preferred; “nano” label required |
| Baby Powders / Diaper Rash Creams | ✅ | 5–20% | Gold Seal or Pharma Grade |
| Deodorants / Soaps | ✅ | 1–10% | Odor control, antimicrobial |
| Rubber (Vulcanization) | ✅ | 3–5 phr | Activator (forms zinc stearate) |
| Paints & Coatings | ✅ | 5–15% | UV absorber, anti-corrosion, opacifier |
| Ceramics & Glass | ✅ | 2–10% | Flux, thermal shock resistance, brightness |
| Plastics & Polymers | ✅ | 0.5–5% | UV stabilizer, antioxidant, antimicrobial |
| Textile Finishes | ✅ | 1–5% | Antimicrobial finish, whiteness |
| Agriculture (Fertilizers) | ✅ | 0.1–0.5% Zn | Foliar or soil application |
| Animal Feed | ✅ | 0.02–0.2% Zn | Immunity and growth support |
| Electronics (Varistors) | ✅ | 1–10% | Piezoelectric, semiconductor |
| Flame Retardants | ✅ | 2–10% | Reduces flammability in plastics/coatings |
| Inks & Pigments | ✅ | 5–20% | White pigment (oil paints, offset inks) |
| Catalyst Support | ✅ | 1–10% | Nanostructured forms preferred |
6. Formulation Examples
A. Sunscreen Lotion (Nano ZnO, SPF 30+)
| Ingredient | % |
|---|---|
| Nano ZnO (coated, 30% dispersion) | 20.0 |
| O/W emulsifier | 5.0 |
| Water | 60.0 |
| Oil phase (caprylic/capric triglyceride) | 10.0 |
| Preservative, glycerin, xanthan gum | 5.0 |
B. Baby Diaper Rash Cream
| Ingredient | % |
|---|---|
| ZnO (Pharma Grade) | 15.0 |
| Petrolatum | 60.0 |
| Lanolin | 15.0 |
| Zinc stearate | 5.0 |
| Vitamin E | 1.0 |
C. Rubber Vulcanization (NR/BR blend)
| Ingredient | phr |
|---|---|
| Natural Rubber (NR) | 100 |
| ZnO (Industrial Grade) | 5 |
| Stearic acid | 2 |
| Sulfur | 2.5 |
| CBS (accelerator) | 1 |
D. Antimicrobial Interior Paint
| Ingredient | % |
|---|---|
| Acrylic emulsion | 40 |
| Water | 25 |
| TiO₂ | 10 |
| ZnO (High Purity) | 5 |
| Calcite | 15 |
| Dispersant, thickener | 5 |
7. Alternatives to Zinc Oxide
| Alternative | Advantages | Disadvantages | Replacement Area |
|---|---|---|---|
| TiO₂ (Titanium Dioxide) | Higher opacity, cheaper | Photocatalytic, UVB only | Paints, plastics, sunscreens |
| Zinc Stearate | Lubricity, water repellency | No UV protection | Cosmetics, mold release |
| Copper Oxide | Stronger antimicrobial | Colored, higher toxicity | Agriculture, antifouling |
| Magnesium Oxide | More alkaline, flame retardant | No UV absorption | Flame retardants, pharma |
| Organic UV Filters (Avobenzone, etc.) | Transparent, high UVA protection | Stability issues, allergy | Sunscreens |
Summary: TiO₂ is the closest alternative, but ZnO’s antimicrobial activity and balanced UV‑A+UV‑B protection make it irreplaceable for baby care and sensitive skin products.
8. Frequently Asked Questions (FAQ)
Q1: Is nano ZnO safe?
A: EU Cosmetic Regulation (EC 1223/2009) allows nano ZnO with mandatory “nano” labeling on the package. Inhalation from sprays is restricted. Skin absorption through healthy skin is negligible.
Q2: Why is ZnO insoluble in water?
A: ZnO has very low water solubility (≤3 mg/L). However, it dissolves in acids or bases, releasing Zn²⁺ ions – this is the source of its antimicrobial effect.
Q3: Why are some sunscreens transparent despite using white ZnO?
A: Nano‑sized ZnO (20–50 nm) does not scatter visible light (400–700 nm) but still absorbs UV – enabling transparent formulations.
Q4: What is the shelf life and storage condition?
A: 3 years in original, unopened packaging. Store in a dry, cool, well‑ventilated area away from moisture and CO₂ (prevents conversion to zinc carbonate).
Q5: Which grade should I choose?
-
Cosmetics & Pharma → Gold Seal or Pharma Grade (≥99.5%, low heavy metals)
-
Rubber & Industrial → Industrial Standard (≥99%)
-
Agriculture → Agricultural Grade (≥70%, economical)
-
Transparent UV protection → Nano Grade + coated
Q6: Is there a risk of metal fume fever?
A: Yes, when melting or heating ZnO to high temperatures, inhaled fumes can cause flu‑like symptoms. Use N95 mask and local exhaust ventilation.
9. Regulatory & Compliance Summary
| Regulation | Requirement |
|---|---|
| EU 1223/2009 (Cosmetics) | Allowed as UV filter; nano form requires labeling |
| REACH / CLP | Registered; respirable fraction classified for dust |
| FDA (OTC Sunscreens) | GRASE Category I |
| Food Contact | Not a direct additive; migration tests required |
| Occupational Exposure | TWA 8h: 5 mg/m³ (respirable dust) |
10. Packaging & Logistics
| Parameter | Detail |
|---|---|
| Packaging Types | 25 kg kraft paper bag (PE liner), 500 kg big‑bag, 1000 kg drum |
| Storage Conditions | Dry (≤60% RH), cool (10–30°C), away from sunlight, separate from acids |
| Shelf Life | 3 years (unopened original packaging) |
| Transport Class | UN 3077 (Environmentally hazardous substance), Class 9, PG III |
11. Occupational Health & Safety
-
Respiratory: P95 or FFP2 mask when dusting
-
Gloves: Nitrile or neoprene
-
Eye protection: Dust‑tight safety goggles
-
Ventilation: Local exhaust (LEV) preferred
-
First aid: If inhaled – move to fresh air; eye contact – rinse with plenty of water
This document serves as a comprehensive reference for Zinc Oxide (ZnO). For specific applications (e.g., nano‑ZnO formulation approval), always verify with the relevant regulatory authority or supplier quality department.
