Maintaining EVA interlayer for laminated glass involves several key practices to ensure its durability, safety, and performance over time. Here’s a detailed guide based on the provided sources:
Storage Conditions: Cool, Dry Place: EVA interlayers should be stored in a cool, dry place away from direct sunlight and moisture. The ideal temperature for storage is between 15-30°C (59-86°F) with a relative humidity of 50% or less. It’s also recommended to store the interlayers in their original packaging to protect them from dust, dirt, and other contaminants. Handling and Processing Moisture Sensitivity: EVA is moisture sensitive when not laminated, and thus requires moisture-tight, aluminum-lined packaging to avoid roll blocking. The temperature of the storage room needs to be below 35°C to prevent roll blocking. For warmer regions, it’s advised to order EVA with a thin interleave foil to avoid self-sticking. Shelf Life: The shelf life of EVA interlayer is considerably shorter than other types, with manufacturers advising a shelf life of 9 months to a maximum of one year. It’s essential to avoid using expired materials as they can show low adhesion and form bubbles during processing or the service life of the laminate. Equipment Cleanliness: Regularly clean the equipment used for EVA processing, as EVA can start to stick and contaminate the workshop easily. This helps in avoiding issues like folded sticking strips on the outer surface of the glass pane during processing, which can be challenging to remove. Post-Laminating: Air Bubble Removal: After laminating, it’s crucial to ensure all air is removed from the laminated stacks to prevent bubbles from forming. This can be achieved through vacuum oven processes or autoclave methods, depending on the specific setup and requirements. It’s important to follow a lamination program that ensures efficient air removal before the laminate is heated to the curing temperature. Curing and Temperature Control: The laminate is typically heated in a vacuum oven to a high temperature (130°C-150°C) for 1 to 3 hours, depending on the laminate’s complexity and size. After lamination, the laminate is cooled under vacuum until it reaches a temperature of 40°C before releasing the vacuum. This cooling period is crucial to ensure the EVA interlayer is strong enough to handle the air rush without causing edge defects. Specific EVA Testing: Gel Content Measurement: The gel content of cured EVA is measured using the Soxhlet extraction method, which helps in ensuring the EVA is properly crosslinked and has good ageing behavior. The gel content should ideally be above 75% for optimal performance.
Conclusion. Maintaining EVA interlayer laminated glass requires careful handling and storage, adherence to specific processing parameters, and regular quality checks to ensure durability and performance. It’s essential to follow best practices for equipment cleanliness and shelf life, and to use appropriate lamination methods to remove air bubbles and achieve proper curing.