Double layer EVA valve bags for Hot-melt road marking

When people mention EVA bags, they always think of a plastic packaging bag made of EVA.

But today, we are going to introduce an innovative product: EVA valve bags. 

What is EVA value bags?

Double-layer EVA (ethylene-vinyl acetate) valve bags are not packaging materials. They are a film-like additive used for hot-melt coatings in road markings.

Why choose EVA value bags?

After mixing and melting 2.5 kg of EVA valve bags with 1 ton of hot-melt coating, significant effects will be exerted on the compressive strength, glass bead adhesion, crack resistance, and weather resistance of the marking coating. 

Parameters of EVA valve bag:

The following is a detailed analysis item by item:  

1. Impact on Compressive Strength (Under 60℃ Condition)  

Requirements of JT/T280-2022: The compressive strength at 60℃ shall be ≥2MPa.  

- For hot-melt coatings with high compressive strength, the marking lines formed are prone to cracking. After adding flexible packaging bags, the crack resistance of the coating will be greatly improved.  

- Softening Effect of EVA Flexible Film Bags: With a low melting point and certain flexibility even at -20℃, they will reduce the overall rigidity of the hot-melt coating.  

- Reduction in Compressive Strength: Traditional hot-melt coatings (petroleum resin + filler) have high rigidity (≥2MPa) at 60℃, but after adding 40 double-layer valve bags, the flexibility of the marking coating is enhanced.  

2. Impact on Glass Bead Adhesion  

- Adhesion Enhancement of EVA Valve Bags:  

  - Improved Molten Wettability: After melting, the flexible film has good fluidity, which can better wrap glass beads and improve the bonding strength.  

  - Elastic Buffering to Reduce Shedding: The high elongation at break of the flexible film bags enables them to undergo elastic deformation under traffic loads, reducing the risk of glass beads shedding due to impact.  

- Practical Effects:  

  - The adhesion rate of glass beads is increased, and their impact resistance is enhanced, delaying the attenuation of the retroreflective brightness coefficient of the marking lines.  

  - The long-term durability is improved, with a higher retention rate of glass beads under dynamic loads, prolonging the reflective life of the marking lines.  

3. Impact on Crack Resistance  

- Toughening Effect of Flexible Film Bags:  

  - Enhanced Stress Dispersion Capacity: The high elongation of the double-layer flexible film bags allows them to absorb the stress caused by road surface shrinkage or traffic vibration, reducing crack propagation.  

  - Improved Low-Temperature Crack Resistance: Below -20℃, the double-layer flexible film bags still maintain flexibility, reducing the risk of low-temperature embrittlement cracking.  

- Practical Effects:  

  - The cracking rate of the new-standard hot-melt marking lines is reduced. Compared with the pure petroleum resin system, the cracking probability can be reduced by 30%-50%.  

  - The number of micro-cracks is decreased, the surface of the marking lines is smoother, and the peeling problem caused by cracks is reduced.  

4. Impact on Coating Weather Resistance  

- Weather Resistance Characteristics of Double-Layer Flexible Film Bags:  

  - UV Resistance: The raw materials of the double-layer flexible film bags are made of EVA + modifiers, which can effectively reduce the yellowing and powdering of the marking coating under long-term ultraviolet irradiation.  

  - Moisture and Heat Resistance: The double-layer flexible film bags have an extremely low moisture absorption rate and do not affect long-term durability in high-temperature and high-humidity environments.  

• Practical Effects:
• The modified EVA double-layer flexible film bags (with anti-aging agents added) can extend the weather resistance life to more than 5 years.  

5. Summary of Comprehensive Impacts  

Adding EVA film-grade packaging bags (40 bags, approximately 2.5 kg of flexible glue added to 1 ton of coating) can reduce the brittleness of hot-melt marking lines and significantly improve the glass bead adhesion, crack resistance, low-temperature toughness, and weather resistance.  

The film-grade double-layer EVA valve-mouth flexible bags can become an economical and effective solution to improve the comprehensive performance of hot-melt marking lines.