Applications, Benefits and Strategies for Preventing Aging and Yellowing of Crosslinked EVAs
- Application of EVA crosslinkers
- Solar Panel Encapsulation
Cross-linked EVA is widely used as an encapsulation material for photovoltaic modules.
It protects solar cells from environmental factors such as moisture, dust and mechanical stress.
Cross-linking improves the material’s durability, UV resistance and thermal stability, which is essential for long-term use in outdoor conditions.
It also improves optical clarity, maximizing the light transmittance of solar cells.
- Wire and Cable Insulation
Cross-linked EVA can be used as an insulation material for wires and cables.
It has excellent electrical insulation properties and better heat resistance.
This material has better resistance to deformation while maintaining flexibility at high temperatures.
It is commonly used in automotive wiring, power cables and telecommunication cables.
- Foam Products
Cross-linked EVA foam is widely used in various industries due to its light weight and excellent shock absorption properties.
Applications include
- Sports equipment (such as soles, protective gear)
- Packaging materials
- Automotive interior parts
- Ship buoyancy aids
Cross-linking improves the foam’s compression resistance and durability.
- Adhesives and Sealants
Cross-linked EVA can be used in hot melt adhesives and sealants.
It improves heat resistance and cohesive strength.
Applications include packaging, bookbinding and building sealants.
Cross-linking helps maintain adhesive properties at higher temperatures.
- Footwear
EVA after cross-linking is widely used in the production of soles and insoles.
It offers a good balance of cushioning, durability and lightness.
Cross-linking increases the material’s resistance to compression and enhances long-term comfort.
It can be used in sports shoes, casual shoes and orthopedic shoes.
- Automotive parts
Cross-linked EVA can be used in a variety of automotive applications:
- Gaskets and seals
- Noise, vibration and jerkiness (NVH) damping elements
- Interior trims
The material has better heat resistance and durability and is suitable for under-the-hood applications.
- Medical devices
Cross-linked EVA is biocompatible and can be used in certain medical applications.
For example
- Orthopedic pads and supports
- Wound dressings
- Drug delivery systems (as a matrix material)
In pharmaceutical applications, cross-linking helps control the release rate of drugs.
- Packaging
Used in specialty packaging applications where heat resistance is a high requirement.
For example
- Shrink wrap films
- Blister packaging
- Hot-fill flexible packaging
- Recreational products
Cross-linked EVA can be used in a variety of sports and leisure products:
- Yoga mats
- Life jackets and buoyancy aids
- Protective gear for contact sports
The material’s cushioning properties, durability, and water resistance make it suitable for these applications.
- Aging and yellowing
Aging and yellowing of EVA (ethylene vinyl acetate) films are common problems that affect their performance and appearance. These problems are primarily caused by polymer degradation due to exposure to UV rays, heat, and oxygen.
Here are some strategies to address these problems:
- UV stabilizers
UV absorbers: These chemicals absorb harmful UV radiation and convert it into heat to dissipate, thereby preventing UV radiation from entering the polymer and causing degradation. Common UV absorbers include benzophenones and benzotriazoles.
Hindered amine light stabilizers (HALS): They work by scavenging free radicals formed during UV exposure, thereby preventing polymer decomposition. HALS are particularly effective because they are long-term stable and regenerate during the stabilization process.
- Antioxidants
Primary antioxidants: These include phenolic antioxidants, which work by donating hydrogen atoms to free radicals, thereby neutralizing them. They are effective in preventing thermal degradation.
Secondary antioxidants: These include phosphites and thioethers, which break down peroxides formed during oxidation into non-radical, non-degrading products. Combining primary and secondary antioxidants provides comprehensive protection against oxidative degradation.
- Heat stabilizers
Adding heat stabilizers to EVA films helps prevent thermal degradation. These stabilizers work by inhibiting degradation mechanisms at elevated temperatures. Common heat stabilizers include metal soaps and organotin compounds.
- Blending with other polymers
Copolymerization: Blending EVA with other polymers, such as polyolefins (such as polyethylene or polypropylene), can improve its stability and resistance to yellowing. Other polymers can dilute the susceptible vinyl acetate content, improving overall durability.
Cross-linking: Cross-linking EVA using peroxides or irradiation can improve its resistance to heat and oxidative degradation. Cross-linked EVA has a stronger network structure and is less susceptible to aging and yellowing.
- Surface treatment
Coating: Applying an anti-UV coating to the surface of the EVA film can provide an additional barrier to UV radiation. These coatings can be made from UV-stable polymers or can be infused with UV stabilizers.
Lamination: Laminating EVA film with a UV-resistant film, such as PET, protects the underlying EVA from direct exposure to UV rays.
