PVI Rubber Accelerator Retarder: Reliable Scorch Protection for Modern Rubber Processing

In high-performance rubber manufacturing, scorch safety is a critical factor that directly affects processing stability, product consistency, and overall production efficiency. PVI rubber accelerator retarder, also known as CTP (N-Cyclohexylthiophthalimide), is widely recognized as one of the most effective anti-scorching agents used in sulfur-cured rubber compounds.

Thanks to its excellent selectivity and thermal stability, PVI has become an essential processing aid for tire manufacturers, industrial rubber goods producers, and compounders worldwide.

What Is PVI Rubber Accelerator Retarder?

PVI is a pre-vulcanization inhibitor designed to delay the onset of vulcanization during mixing, extrusion, and calendering stages—without negatively affecting the final curing speed or mechanical properties of rubber products.

Unlike traditional retarders that may reduce crosslink density or prolong cure time, PVI rubber accelerator retarder works selectively, suppressing premature scorch while allowing normal vulcanization at curing temperature.

Chemical name: N-Cyclohexylthiophthalimide
CAS No.: 17796-82-6
Common name: PVI / CTP

Key Technical Advantages of PVI Retarder

1. Excellent Scorch Delay Performance

PVI significantly extends Mooney scorch time (t₅) and scorch safety margin without compromising cure rate at higher temperatures.

In typical NR and SBR compounds, adding 0.1–0.3 phr PVI can increase scorch time by 30–60%, improving processing safety during high-shear operations.

2. No Adverse Effect on Final Vulcanization

At curing temperatures above 140–150 °C, PVI decomposes and becomes inactive, allowing accelerators such as CBS, TBBS, MBTS, or DCBS to function normally.

• No reduction in torque
• No loss of tensile strength
• No negative impact on elongation or abrasion resistance

3. Wide Compatibility with Rubber Polymers

PVI rubber accelerator retarder is suitable for:

• Natural Rubber (NR)
• Styrene-Butadiene Rubber (SBR)
• Butadiene Rubber (BR)
• Nitrile Rubber (NBR)
• EPDM (sulfur curing systems)

4. Excellent Processing Stability

PVI remains stable during storage and mixing, making it ideal for:

• High-temperature internal mixing
• Long extrusion cycles
• Complex compound formulations

Typical Technical Specifications

Specifications can be customized based on application requirements.

Practical Application Case

Tire Tread Compound (NR/SBR blend)

• Accelerator system: CBS + MBTS
• Issue: Scorch during extrusion at 115–120 °C
• Solution: Addition of 0.2 phr PVI

Results:

• Scorch time (t₅) increased by ~45%
• No change in optimum cure time (t₉₀)
• Improved extrusion stability
• Reduced scrap rate by over 20%

This demonstrates why PVI rubber accelerator retarder is widely used in tire manufacturing and technical rubber goods.

Recommended Dosage

• Typical dosage: 0.1–0.3 phr
• Higher levels may be used in compounds with high accelerator loading or extreme processing conditions

PVI works best when added during the final mixing stage to ensure uniform dispersion.

Why Choose High-Quality PVI Retarder?

Using low-purity or unstable retarder materials may lead to inconsistent scorch protection or unexpected curing behavior. A high-purity PVI rubber accelerator retarder ensures:

• Consistent batch-to-batch performance
• Improved processing window
• Reduced risk of premature vulcanization
• Higher production efficiency

Conclusion

As rubber processing becomes faster and more demanding, PVI rubber accelerator retarder plays a crucial role in safeguarding production stability. Its unique ability to delay scorch without affecting final vulcanization makes it an indispensable additive in modern rubber compounding.

For manufacturers seeking reliable scorch control, improved processing safety, and consistent product quality, PVI remains the industry’s trusted solution.