Understanding the Two BIPB CAS Numbers
The peroxide crosslinking market frequently encounters two distinct CAS registry numbers for bis(tert-butylperoxyisopropyl)benzene: CAS 25155-25-3 and CAS 2212-81-9. While both refer to BIPB compounds, they represent fundamentally different products with distinct isomeric compositions, physical properties, and application characteristics. Understanding these differences is essential for formulators, procurement professionals, and quality control specialists working in the polymer crosslinking industry.
Key Facts: BIPB CAS Comparison
- CAS 25155-25-3: Mixed-isomer BIPB (60-70% meta + 30-40% para)
- CAS 2212-81-9: Pure meta-isomer BIPB (1,3-substituted)
- Physical Form (25155-25-3): Waxy solid/semi-solid at ambient
- Physical Form (2212-81-9): Crystalline solid with higher melting point
- Market Share: CAS 25155-25-3 represents >90% of commercial BIPB volume
- Cost: CAS 2212-81-9 typically 20-40% more expensive
Chemical Structure Comparison
| Property | CAS 25155-25-3 | CAS 2212-81-9 |
|---|---|---|
| IUPAC Name | 1,3(4)-Bis(2-tert-butylperoxyisopropyl)benzene | 1,3-Bis(2-tert-butylperoxyisopropyl)benzene |
| Isomeric Composition | ~60-70% meta + ~30-40% para + trace ortho | >97% meta (1,3-) isomer |
| Molecular Formula | C20H34O4 | C20H34O4 |
| Molecular Weight | 338.49 g/mol | 338.49 g/mol |
| Melting Point | 45-55 deg C (broad range due to isomer mix) | 48-52 deg C (sharp, pure compound) |
| Active Oxygen | 9.4-9.6% | 9.45% (theoretical) |
Performance Differences
While both BIPB grades function as effective crosslinking agents, subtle performance differences arise from their isomeric compositions:
Crosslinking Efficiency
The pure meta-isomer (CAS 2212-81-9) typically exhibits slightly higher crosslinking efficiency in certain polymer systems, attributed to its uniform molecular structure and consistent decomposition kinetics. However, the mixed-isomer product (CAS 25155-25-3) provides entirely adequate performance for the vast majority of commercial applications and offers superior cost-effectiveness.
Processing Characteristics
CAS 25155-25-3’s mixed isomer composition results in a broader melting range, which can facilitate easier incorporation and dispersion in some polymer compounding operations. The pure meta-isomer’s sharper melting point may require more precise temperature control during incorporation.
Scorch Safety
Both grades offer excellent scorch safety compared to DCP, with minimal premature crosslinking during compounding. The slight difference in decomposition kinetics between the meta- and para-isomers in the mixed product can provide a marginally broader processing window under certain conditions.
Application Guidance
Use CAS 25155-25-3 (Mixed Isomer) When:
- Cost-effectiveness is a primary consideration
- Your application is standard PEX, XLPE, EVA encapsulation, or general rubber vulcanization
- Processing conditions are well-established and reproducible
- End-product odor requirements are met by standard BIPB performance
Consider CAS 2212-81-9 (Pure Meta-Isomer) When:
- Ultra-high purity is required (e.g., sensitive electronic or medical applications)
- Tight specification control is needed for regulated end uses
- Processing conditions are at the margin of BIPB stability limits
- Slightly different crosslinking kinetics are desired
Frequently Asked Questions
Q: Which CAS number should I specify on my purchase order?
A: For most commercial applications, CAS 25155-25-3 is the appropriate specification, as this represents the standard commercial mixed-isomer product that is widely available and cost-effective. If your application specifically requires the pure meta-isomer (e.g., for regulatory, performance, or purity reasons), specify CAS 2212-81-9. Always confirm with your supplier which grade they are providing to ensure alignment with your quality specifications.
Q: Are there differences in safety classification between the two BIPB types?
A: Both CAS 25155-25-3 and CAS 2212-81-9 are classified as Organic Peroxide Type D (UN 3106 for solid formulations). The safety data sheets and hazard classifications are essentially identical for both products. The primary differences lie in physical properties (melting behavior, handling characteristics) rather than intrinsic hazard profiles.
Key Takeaways
- CAS 25155-25-3 (mixed isomer) and CAS 2212-81-9 (pure meta-isomer) are chemically distinct BIPB products.
- The mixed-isomer product dominates commercial markets due to excellent performance and cost-effectiveness.
- Pure meta-isomer is reserved for specialized applications requiring ultra-high purity or specific kinetic behavior.
- Both grades share the same molecular formula, molecular weight, and safety classification.
- Shandong Do Sender Chemicals offers both BIPB grades with consistent quality and comprehensive technical support.