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        # Why Your CPW Turns Black at 180°C: The Science of Thermal Stability

        

**Topic:** Technical

        

You've just loaded a fresh batch of PVC compound into the extruder. Ten minutes in, the melt starts to discolor. Within twenty, it's charring. The culprit? Your Chlorinated Paraffin (CPW) is failing the heat test.

        
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## Problem

Most standard-grade CPW begins to degrade rapidly above 160°C. In high-speed extrusion lines for cables or rigid pipes, temperatures often spike to 180°C or higher. If the CPW isn't properly stabilized or has a high volatile content, it releases hydrochloric acid, which acts as a catalyst for further degradation, leading to 'blackening' and brittle products.

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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 Diamond Grade CPW is engineered with a specific carbon chain length and advanced stabilization packages. It is tested to remain pale yellow even after 30 minutes at 180°C. By switching to a high-stability grade, manufacturers can reduce reject rates by up to 12% and ensure consistent color in heat-sensitive applications like white cables, clear profiles, and premium footwear.

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          ## Frequently Asked Questions

          
### Does higher chlorine content mean better heat stability?

Not necessarily. Stability depends more on the carbon chain quality and the stabilization additives used during manufacturing.

### Can I add my own stabilizers to fix cheap CPW?

While possible, it's rarely cost-effective compared to buying a pre-stabilized high-grade CPW like NBT Diamond.

        
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By NBT Technical Desk · Updated 2026-06-07

        

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