Peroxide Vulcanization vs. Sulfur Vulcanization
Traditional rubber vulcanization uses sulfur to create polysulfide crosslinks. While sulfur cure is low-cost and provides good flexibility, peroxide vulcanization creates carbon-carbon crosslinks that deliver superior heat resistance, lower compression set, and better aging performance. For applications above 125°C or requiring long-term heat aging, peroxide cure is the industry standard.
| Property | Peroxide Cure | Sulfur Cure |
|---|---|---|
| Crosslink type | C–C (strong, stable) | Polysulfide (weaker) |
| Heat resistance | Excellent (>150°C continuous) | Moderate (<125°C) |
| Compression set | Low (<20%) | Higher (20–40%) |
| Aging performance | Excellent | Moderate (sulfur reversion) |
| Cost | Higher (peroxide + co-agent) | Lower |
Key Peroxide Types for Rubber
1. Dicumyl Peroxide (Perodox DCP)
The most widely used rubber crosslinking peroxide. Suitable for EPDM, natural rubber (NR), SBR, and NBR.
- Typical dosage: 0.5–2.5 phr (rubber); plus 0.5–2.0 phr co-agent (e.g., TAC, TAIC)
- Scorch safety: Moderate; use in compounds with processing temp <120°C
2. 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane (Perodox 101)
Excellent scorch safety, making it the preferred choice for injection molding and extrusion of complex rubber profiles where the compound experiences high shear and temperature.
- Typical dosage: 0.3–2.0 phr + co-agent
- Applications: EPDM window seals, hose covers, silicone rubber gaskets
3. tert-Butyl Perbenzoate (Perodox 117)
Lower decomposition temperature, suitable for heat-sensitive rubber compounds or when using high-activity co-agents.
4. 2,5-Dimethyl-2,5-di(tert-butylperoxy)-3-hexyne (Perodox 14)
Specialized for silicone rubber and fluoroelastomer crosslinking. The –C≡C– spacer provides unique flexibility in the crosslinked network, resulting in low compression set and excellent heat aging.
Co-Agents: Critical for Peroxide Cure Efficiency
Peroxide cure requires a co-agent to achieve high crosslink density and good mechanical properties. The co-agent is a polyfunctional monomer that captures the polymer radical and forms additional crosslinks.
| Co-Agent | Chemical Type | Best For |
|---|---|---|
| TAIC | Triallyl isocyanurate | EPDM, general purpose |
| TAC | Triallyl cyanurate | High-performance EPDM |
| TMA | Trimethylolpropane trimethacrylate | NBR, CR, high hardness |
| HVA-2 | N,N’–m-Phenylene dimaleimide | EPDM, heat-resistant compounds |
Frequently Asked Questions
Q: Do I always need a co-agent with peroxide cure?
A: Yes, for most rubber compounds. Without a co-agent, the crosslink density will be low and mechanical properties poor. The only exception is some specialty fluoroelastomers where the peroxide alone provides sufficient crosslinking.
Q: Can I use peroxide cure in natural rubber (NR) for tires?
A: Peroxide cure is not typically used for tire treads (sulfur provides better fatigue resistance). However, peroxide cure is used for tire inner liners, sidewalls, and engine mounts where heat resistance is critical.
Q: How do I select the right co-agent for my EPDM compound?
A: TAIC is the industry standard for EPDM. For higher-performance requirements (lower compression set, higher hardness), use TAC. For cost-sensitive applications, HVA-2 is an effective alternative. Laboratory MDR screening is recommended.
Do Sender Rubber Vulcanization Solutions
Shandong Do Sender Chemicals Co., Ltd. supplies a full range of Perodox® organic peroxides for rubber vulcanization, plus technical support for co-agent selection and MDR scorch safety evaluation. Our products meet REACH, ISO 9001, and ASTM standards.
Contact our technical team for a customized peroxide + co-agent package for your EPDM, silicone, or fluoroelastomer compound.