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        # Fire-Safe Conveyor Belts: CPW Formulation for Mining & Industry

        

**Topic:** Technical

        

An underground mine conveyor catches fire. The belt burns for hours, filling the tunnel with toxic smoke and trapping workers. The investigation reveals: the belt had no flame retardant system. This is preventable.

        
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## Problem

Conveyor belts used in mining, power plants, and enclosed industrial facilities are required to meet strict fire safety standards (IS 1891 Part 4 for flame resistance in India). Standard rubber compounds using only carbon black and process oils offer zero flame retardancy. Achieving fire safety typically required expensive additives like ATH (Aluminium Trihydrate) at very high loadings (100+ PHR), which drastically increases compound viscosity, reduces tensile strength, and makes calendering extremely difficult.

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## Likely cause

This issue often stems from inconsistent compounding temperatures, inferior raw material purity, or unbalanced stabilizer ratios within the formulation matrix.

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## Corrective direction

**NBT High-Chlorine CPW (60-68% Cl₂)** provides flame retardancy at just **20-30 PHR** in CR (Chloroprene) or SBR rubber compounds  -  a fraction of the loading required by ATH alone. CPW acts as both a flame retardant (chlorine radical mechanism) and a processing aid (reducing compound viscosity for easier calendering). When combined with a moderate loading of ATH (30-50 PHR) and Antimony Trioxide (3-5 PHR) as a synergist, this system easily passes the IS 1891 flame propagation test while maintaining tensile strength above 12 MPa and elongation above 300%. Our Bawana facility stocks both 60% and 68% chlorine grades in bulk ready for dispatch.

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          ## Frequently Asked Questions

          
### Does CPW affect the rubber-to-fabric adhesion?

At recommended loadings, no. However, excessive CPW (>35 PHR) can reduce adhesion to textile reinforcement. Keep within 20-30 PHR.

### Can this system pass international standards like DIN 22100?

Yes, with proper optimization. We have helped clients achieve both IS and DIN fire safety certification.

        
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By NBT Technical Desk · Updated 2026-06-07

        

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