Pain point you may have faced
You produce large, thick natural rubber articles – heavy truck tires, giant earthmover treads, or thick rubber pads. Conventional accelerators like TBBS need PVI to achieve acceptable scorch safety, but even then, reversion during long cure cycles kills physical properties. Worse, in steel‑cord reinforced applications (e.g., tire belts, bead fillers), the adhesion between rubber and brass‑plated steel degrades rapidly under heat and humidity. You have also noticed that some accelerators lose effectiveness when the compound gets damp or during prolonged storage.

Why TBSI‑75 is different
First® TBSI‑75 is a post‑curing, eco‑friendly accelerator specifically designed for natural and synthetic rubbers – particularly effective in high‑alkalinity carbon black compounds. It offers excellent scorch resistance, keeping you safe even at elevated processing temperatures, while delivering fast vulcanization and outstanding reduction resistance (no reversion). Unlike TBBS, TBSI‑75 can effectively replace the TBBS + PVI system in large, thick natural rubber products – simplifying your formulation without sacrificing safety.

What makes it unique

High molecular weight & high melting point – less volatility, cleaner factory air.

Superior thermal stability – remains stable even when the rubber compound is exposed to water or high humidity.

Enhances steel cord adhesion – significantly improves the heat resistance and durability of the bond between rubber and brass‑plated steel cords, critical for tire belts, bead wires, and hose reinforcements.

What you gain

One accelerator replaces two – no need for separate PVI, reduce inventory and dosing errors.

No reversion – thick parts maintain tensile strength, tear resistance, and modulus.

Water‑stable – compound stays consistent even in humid environments or after rain exposure on the mill.

Longer lasting adhesion – steel cord bond survives higher service temperatures and longer aging.

Real‑world result
A steel‑cord conveyor belt manufacturer was using TBBS + PVI in their thick (25 mm) belt cover compound. They experienced reversion spots and occasional adhesion failure after heat aging. After switching to First® TBSI‑75 at the same total phr (1.2 phr, without PVI), scorch safety actually improved, cure time remained similar, and heat‑aged adhesion values (measured after 7 days at 100°C) increased by 40%. The belt passed ISO 15236 requirements without any formulation rework.

Typical specifications

Appearance: light gray to off‑white granules

Active ingredient: N‑tert‑butyl‑bis(2‑benzothiazole) sulfenimide (approx. 75%)

Carrier: EPDM/SBR

Recommended dosage: 0.8–1.5 phr (as primary accelerator, no PVI needed for most recipes)

Packaging: 25 kg carton with inner PE liner

Storage: 12 months in unopened packaging, cool and dry (tolerant to brief moisture exposure)

Samples and technical data sheets are available. No hard selling — just for your evaluation.