Introduction
Dilauroyl peroxide (LPO, CAS 105-74-8) is a symmetrical diacyl peroxide derived from lauric acid. As one of the most widely available diacyl peroxides, LPO occupies an important position in the organic peroxide product portfolio, serving as a medium-temperature initiator for polymerization and a curing agent for elastomers. This comprehensive guide examines its properties, decomposition chemistry, industrial applications, and safety management.
Key Facts: Dilauroyl Peroxide
- CAS Number: 105-74-8
- IUPAC Name: Didodecanoyl peroxide
- Molecular Formula: C24H46O4
- Molecular Weight: 398.62 g/mol
- Appearance: White powder, flakes, or pastilles
- Melting Range: 53-57 deg C
- Active Oxygen: ~4.01% (theoretical); 3.8-4.0% (commercial)
- 10-Hour Half-Life: ~62 deg C (in benzene)
- 1-Hour Half-Life: ~80 deg C
- SADT: ~50 deg C (neat); formulations may differ
Physical and Chemical Properties
| Property | Value |
|---|---|
| Appearance | White powder or flakes |
| Density | ~0.9 g/cm3 |
| Bulk Density | 0.4-0.6 g/cm3 |
| Active Oxygen | 3.8-4.0% |
| Solubility in Water | Insoluble |
| Solubility in Organics | Soluble in benzene, chloroform, oils; slightly soluble in ethanol |
| Flash Point | >70 deg C |
Decomposition Chemistry
Upon thermal decomposition, LPO undergoes homolytic O-O bond cleavage to generate two lauroyloxy radicals. These primary radicals can decarboxylate to form undecyl radicals and CO2. The decomposition products include undecane, carbon dioxide, and lauric acid, which are relatively benign and non-aromatic, distinguishing LPO from benzoyl peroxide which produces aromatic decomposition products.
Key Applications
1. PVC Polymerization
LPO serves as a low-to-medium temperature initiator for suspension and mass PVC polymerization. Its decomposition kinetics in the 55-70 deg C range are suitable for general-purpose PVC grades and copolymers. LPO is often used in combination with other initiators to achieve the desired polymerization rate profile.
2. Polyethylene Crosslinking
In peroxide crosslinking of polyethylene, LPO can function as a co-initiator alongside higher-temperature peroxides, providing radical generation in the early stages of the heating cycle and contributing to more uniform crosslink distribution.
3. Silicone Rubber Curing
LPO is employed as a curing agent for certain silicone elastomer formulations, particularly where lower cure temperatures are desired compared to DCP or BIPB systems.
4. Food and Cosmetic Applications
Historically, LPO has been used as a bleaching agent for flour and edible oils, though regulatory restrictions have limited this application in many regions. Its GRAS (Generally Recognized As Safe) status for certain food applications has been evaluated in various jurisdictions.
Safety and Handling
LPO is classified as Organic Peroxide Type D (UN 3106 for solid formulations). Key handling considerations include:
- Storage at temperatures not exceeding 25-30 deg C
- Protection from direct sunlight and heat sources
- Avoidance of contamination with acids, bases, reducing agents, and accelerators
- Use of grounded, non-sparking equipment
- Water spray or fog for firefighting
Frequently Asked Questions
Q: What differentiates LPO from benzoyl peroxide for polymerization applications?
A: Key differences include: (1) LPO has a lower 10-hour half-life temperature (~62 deg C vs. ~73 deg C for BPO), making it more reactive at lower temperatures; (2) LPO’s decomposition products (lauric acid, undecane, CO2) are aliphatic and relatively benign, while BPO produces aromatic decomposition products (benzene derivatives); (3) LPO’s active oxygen content is lower (4% vs. 6.6%), requiring higher dosage by weight; (4) BPO generally requires phlegmatization with water, while LPO is available in dry form.
Q: Is LPO approved for food contact applications?
A: Regulatory status varies by jurisdiction. In the United States, LPO has been evaluated for certain food contact uses under FDA regulations. In the European Union, specific migration limits may apply. In China, LPO was previously used as a flour treatment agent but has been restricted since 2011. Always verify current regulatory status for the specific application and region before use.
Key Takeaways
- Dilauroyl peroxide (LPO, CAS 105-74-8) is a versatile diacyl peroxide with a T10h of ~62 deg C.
- Applications span PVC polymerization, polyethylene crosslinking, silicone curing, and (historically) food processing.
- Its aliphatic decomposition products are relatively benign compared to aromatic diacyl peroxides like BPO.
- Lower active oxygen content (4%) requires higher dosage by weight but provides specific handling advantages.
- Shandong Do Sender Chemicals supplies high-purity LPO for industrial polymerization and crosslinking applications.