Introduction
Benzoyl peroxide (BPO, CAS 94-36-0) is arguably the most recognizable organic peroxide, with applications spanning industrial polymer chemistry, pharmaceutical dermatology, food processing, and consumer products. This comprehensive guide consolidates the essential knowledge about BPO’s properties, reaction chemistry, diverse applications, and critical safety requirements.
Key Facts: Benzoyl Peroxide
- CAS Number: 94-36-0
- IUPAC Name: Dibenzoyl peroxide
- Molecular Formula: C14H10O4
- Molecular Weight: 242.23 g/mol
- Appearance: White granular powder (phlegmatized)
- Active Oxygen: 6.6% (theoretical); 4.6-5.0% for 70-75% water-wet grade
- Melting Point: 103-106 deg C (decomposes)
- 10-Hour Half-Life: ~73 deg C
- SADT: ~80 deg C (desensitized ~60 deg C)
- UN Classification: UN 3104 (water-wet, >=20% H2O)
Physical and Chemical Properties
| Property | Value |
|---|---|
| Appearance | White granular powder |
| Density | 1.33 g/cm3 |
| Bulk Density | 0.5-0.7 g/cm3 |
| Solubility in Water | <0.01 g/100 mL (insoluble) |
| Solubility in Organics | Soluble in benzene, chloroform, acetone, ethyl acetate |
| Auto-Ignition Temperature | ~80 deg C (dry form) |
| Decomposition Products | Benzoic acid, benzene, CO2, phenyl radicals |
Decomposition Chemistry
BPO decomposes via two primary pathways: (1) homolytic O-O bond cleavage generating benzoyloxy radicals, and (2) induced decomposition where radicals attack unreacted BPO molecules. The benzoyloxy radicals can decarboxylate to phenyl radicals and CO2, or abstract hydrogen from the surrounding medium to form benzoic acid.
Multi-Industry Applications
1. Polymer Industry
BPO is a widely used initiator for free-radical polymerization of styrene, acrylates, and unsaturated polyesters. It also serves as a crosslinking agent for silicone rubber and a curing agent for UPR with amine accelerators.
2. Pharmaceutical/Cosmetic Industry
BPO is an FDA-approved OTC drug for acne treatment, available in concentrations of 2.5-10% in various topical formulations. The global acne treatment market exceeds USD 7 billion annually.
3. Food Industry
Historically used as a flour bleaching agent at 20-50 ppm, though regulatory restrictions apply in many regions including China (since 2011) and the EU.
4. Other Applications
BPO is used in hair bleaching products, teeth whitening systems, and as a polymerization initiator for bone cement in orthopedic surgery.
Safety: The Critical Distinction
Pure, dry BPO is impact- and friction-sensitive and can decompose explosively. ALL commercial BPO products are phlegmatized (desensitized) — typically with >=20% water for industrial grades or with plasticizers for paste formulations. NEVER allow water-wet BPO to dry out. The resulting dry material poses a severe explosion hazard.
Frequently Asked Questions
Q: How can I verify that my BPO has not dried out during storage?
A: Regular inspection of the container integrity and visual assessment of the product appearance are the first line of defense. Water-wet BPO should appear as a moist, free-flowing powder — not as dry, clumped, or crusty material. The water content can be verified analytically using Karl Fischer titration or loss-on-drying methods. If there is any doubt about the water content or if the material appears dry, contact the supplier immediately and do not handle the material further until expert guidance is obtained.
Q: What distinguishes pharmaceutical grade BPO from industrial grade?
A: Pharmaceutical grade BPO must comply with pharmacopoeial monographs (USP, EP, BP) that specify purity (>98% on dried basis), limits on related substances (benzoic acid, ethyl benzoate, benzaldehyde), heavy metals, and residual solvents. Manufacturing must follow GMP requirements including validated processes, controlled environments, and comprehensive quality testing. Industrial grade BPO is typically supplied at 70-75% purity (water-wet) and is not manufactured to pharmaceutical standards.
Key Takeaways
- Benzoyl peroxide (CAS 94-36-0) is the most versatile organic peroxide, spanning industrial, pharmaceutical, and consumer applications.
- Commercial BPO is ALWAYS phlegmatized — never handle dry BPO.
- Applications include polymer initiation, silicone curing, acne treatment, and flour bleaching (where permitted).
- Pharmaceutical grade BPO requires GMP manufacturing and compliance with pharmacopoeial specifications.
- Shandong Do Sender Chemicals supplies industrial-grade BPO for polymerization and crosslinking applications with rigorous quality and safety standards.