Comparing scorch safety in CBS powder and predispersed masterbatch

Can CBS and TBBS be exchanged at equal weight?

Dosing by total product mass changes both active CBS and carrier. A greater commercial mass of masterbatch may deliver the same active dose.

Separate the carrier effect on an active CBS basis

Calculate active CBS in the compound and fix sulfur and the other accelerators. Sample the same compound lot for scorch and cure curves and compare dispersion and surface defects.

Comparing active accelerator additions

If the masterbatch contains 80% CBS, each 1 kg supplies 0.8 kg CBS and 0.2 kg carrier. Prepare controls on an equal-active basis and enter the carrier difference separately in the formulation.

Does a higher masterbatch addition than powder mean lower efficiency?

Remove the carrier contribution and compare at equal active CBS, then assess dispersion and performance. Tire compounds: In one formulation, compare cure curves, scorch time and finished-part performance. Continuous mixing: Within the specified processing window, compare granule dispersion, stability and lot variation.

Checking CBS assay and Melting point or initial melting point

CBS assay (% by mass): Verify the analytical method and commercial form. Melting point or initial melting point (°C): Evaluate using the specified method and purity specification. Sieve residue or dispersion (% or grade): For powder, specify sieve aperture. For masterbatch, assess dispersion in the rubber compound.

What to record

• Active CBS dose
• Carrier
• Scorch time
• Cure curve
• Appearance

Technical references

• LANXESS CBS rubber accelerator catalogue ↗

Products and processes