GANA Laminating Session Offers Tips to Ensure Quality Laminated Glass

The use of laminated glass in architectural applications, whether for safety and security purposes or even sound control, has seen much growth over the past few years. As a result more and more glass fabrication companies have added laminated glass production to their capabilities. But how does a company ensure the best possible quality during pre-pressing and autoclaving? Dan Laporte from Solutia Inc. discussed some of those issues during his presentation this morning, which was part of the Glass Association of North America's laminating session during the Glass Fabrication & Glazing Educational Conference taking place in Cincinnati.

In order to ensure proper PVB-glass lamination, Laporte said fabricators should focus on these key areas:

• Storage and roll handling;
• Glass preparation;
• Assembly and trimming;
• Tacking, deair and sealing; and
• Autoclaving.

When talking about storage and handling, Laporte discussed the importance of maintaining the packaging integrity; this will help keep out moisture and contamination. PVB, he explained, has sponge-like characteristics and it will suck up water.

PVB is also an adhesive and will stick to itself if not packaged and stored properly.

"So store the PVB in a temperature between 40-50 degrees F," said Laporte. He also recommended that the PVB rolls be used on a first in-first out basis.

Cutting, cleaning and preparing the glass for lamination is also important. Some of the points Laporte offered included making sure the glass cutting equipment is in good working conditions so that glass pieces are cut neat and evenly; changing the glass washing tank regularly and using a washing temperature of the water between 120-140 degrees F; and also drying the glass thoroughly and uniformly.

When it comes to assembling the glass, a proper clean room environment is also critical to producing quality laminated glass. Laporte recommended keeping the clean room relative humidity between 20-35 percent and ambient temperature between 55-72 degrees F.

The cleanliness of the room is critical.

"I can't over emphasize this," said Laporte. "The room has to be ultra clean. If it's not, the PVB will pick up contaminants [which will end up as part of the glass]." Some suggestions he offered included having double entry doors leading to the clean room so that will help ensure you're not bringing in the factory floor environment, and also tacky mats which can help ensure you're not bringing in dirt from shoes.

Other assembly recommendations included:

• Unrolling the PVB directly from the unwind stand;
• Avoiding contact with the floor, walls and non non-clean surfaces;
• Avoiding pulling or excess tension on the sheet;
• Cutting with sharp blades; and
• Covering stacked PVB with clean Polyethylene.

He also talked about tacking, deairing and sealing steps.

Tacking occurs at assembly and maintains sheet position. "This prevents glass offset and promotes [flat positioning]," said Laporte. Deairing is a way to remove excess air. It also helps tack the glass to the interlayer and promotes edge seal. And sealing prevents air penetration during autoclaving.

When it comes to autoclaving, this process creates a viscous flow of the interlayer; optimizes optical properties; dissolves residual air; and finalizes the adhesive bond.

Laporte's autoclaving recommendations include:

• Minimizing the pressure points on the glass;
• Securing the glass on rack while in the autoclave to keep it from moving around;
• Ensuring proper air flow;
• Keeping anything flammable out of the autoclave; and
• Running burnout cycles.

GANA's Glass Fabrication & Glazing Educational Conference concludes this afternoon.