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        # Plasticizer Migration in PVC: Why Your Product Gets Sticky and How to Stop It

        

**Topic:** Explainer

        

In the hot and humid climates of India, South Asia, and Africa, plasticizer migration is a major cause of flexible PVC product failure. Under high ambient temperatures (up to 48°C), standard plasticizers like [NBT DOP](/products/plasticizers/dop) migrate to the surface, leaving the PVC brittle and the surface sticky. To prevent this, formulators use low-migration plasticizers like [NBT DOTP](/products/plasticizers/dotp) or high-molecular-weight [NBT TOTM](/products/plasticizers/totm) to ensure product durability in tropical climates.

        
        
        
        
        
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          ## Frequently Asked Questions

          
### Why does my PVC product get sticky after a few months?

This is plasticizer bloom  -  the plasticizer has migrated to the surface. The most common causes are: (1) using too high a ratio of secondary plasticizer (CPW) to primary plasticizer, (2) using DOP above its compatibility limit in a specific formulation, or (3) service temperature higher than the compound was designed for.

### Does higher plasticizer loading always increase migration?

Yes, to a point. Above the compatibility threshold of a plasticizer in the specific PVC grade, any additional loading will accelerate migration. Below the threshold, higher loading increases flexibility without necessarily increasing migration rate significantly.

### What is the difference between migration and volatilization?

Migration is the movement of plasticizer within the solid to the surface. Volatilization is the evaporation of plasticizer from the surface into the air. Both reduce plasticizer content  -  migration is the rate-limiting step for most service conditions, but at high temperatures, volatilization can become the dominant loss mechanism.

### Can I prevent migration by using a higher-viscosity PVC resin?

Higher molecular weight PVC (higher K-value, e.g., K-70 vs K-65) has a tighter polymer network that does reduce plasticizer diffusion coefficients. However, it also requires higher processing temperatures and higher plasticizer loading for the same flexibility  -  the net migration benefit is often modest. Plasticizer molecular weight is a more reliable lever.

        
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By NBT Technical Desk · Updated 2026-07-04

        

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