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        # Understanding EVA Resin: Vinyl Acetate Content and Shoe Sole Foam Formulations

        

**Topic:** Explainer

        

Ethylene-Vinyl Acetate (EVA) is the dominant polymer for producing lightweight, cushioned shoe soles and insoles in major footwear hubs like Bahadurgarh, Agra, and Kanpur. The vinyl acetate (VA) content (typically 18% to 28%) determines the crystallization, elasticity, and expansion ratio of the molded foam.

        
        
        
        
        
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          ## Frequently Asked Questions

          
### Why is DCP cross-linking necessary in EVA foaming?

DCP cross-links the EVA polymer chains, building the melt viscosity and strength required to trap nitrogen gas. Without cross-linking, the gas bubbles would collapse, resulting in a dense, solid part.

### What is the difference between EVA 18% and EVA 28%?

EVA 28% has higher vinyl acetate content, making it softer, more flexible, and more resilient with a rubbery feel, whereas EVA 18% is stiffer and offers better support for structural mid-soles.

### Can EVA resin be processed in PVC extrusion machines?

Yes, but require thorough purging. EVA is processed at lower temperatures (140-180°C). Any residual PVC in the barrel will degrade at these temperatures, and residual EVA can cross-link if overheated.

### What is the CAS number for EVA copolymer?

The CAS registry number for Ethylene-Vinyl Acetate copolymer is 24937-78-8.

        
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By NBT Technical Desk · Updated 2026-07-04

        

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