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Volume 6   Issue 5                June 2005

Hot-Melt Glazing Systems Provide 
Competitive Edge Over Overseas Imports 

by Mark Smith

Foreign imports, especially from countries such as China, have climbed steadily in recent years. To maintain market share and a competitive edge, American businesses have been forced to increase their efforts in various domestic markets, including the fenestration industry. Recent studies by China’s National Development and Reform Commission show that 2005 exports increased dramatically by 35 percent over last year’s first-quarter figures, while imports rose at a slower pace of 15 percent.

As a result, U.S. manufacturers are upgrading production methods strategically to uphold, or even expand, their market share. For instance, many producers of glazing/bedding compounds for windows and doors have moved away from traditional methods in the last five years. Methods such as labor-intensive tapes and slow-drying wet sealants are gradually being replaced by a quicker, more durable green strength product: hot-melt glazing systems. 

Glazing Tape vs. Wet Sealants
For nearly 30 years, tape and liquid-applied (wet) compounds have dominated the sealant industry for window and door manufacturers. Due to their pre-cured qualities, glazing tapes were considered the product-of-choice by many manufacturers because they allowed a window sash to be processed immediately. Tapes are also UV-resistant so they will not break down to exposure from sunlight and can be utilized in hot, cold or humid climates.

Manually applied butyl tapes may afford manufacturers significant equipment cost savings on the front side, but could lead to elevated labor costs from inconsistent applications due to lack of automation. Additional inventory expenses also occur since various tape sizes must be stored, proving more difficult and costly than maintaining drums for wet sealants. Because they are applied manually, tape products cannot be used for automation and limit a fenestration company’s ability to increase productivity.

In comparison, certain window and door manufacturers have favored wet sealants because they work well with XY tables for precise placement of compounds such as silicone, waterborne or solvent materials. A high rate of production and reasonable level of quality over the years have led manufacturers to prefer these liquid-applied products, especially silicone. Like tapes, wet sealants are also UV and weather resistant.

However, wet sealants require a longer cure time to ensure that the glass adheres to its finished sash. In its uncured state, glass can shift from movement in the factory, or even during shipment, and result in sealant wet out or excess flash out. Delays in the curing process can arise from a lack of oxygen caused by air-tight packaging materials. Extra floor space is also necessary so finished sashes can cure prior to shipping, which leads to additional capital expenditures for storage. 

In addition, silicone-based wet sealants are challenging because they can lead to several mechanical or maintenance issues. Excess material on the sash or glass, resulting from wet out, can easily defect the final piece since silicone cannot be painted over easily.

Furthermore, silicone clean up is extremely difficult because it is hard to remove from equipment and work spaces.

Many smaller manufacturers prefer the cost-efficient tape method, despite its labor-intensive requirements, in great part because they may lack the necessary capital to finance purchasing automated equipment. Large-volume manufacturers tend to utilize both glazing processes for use with different applications. But the new hot-melt glazing technology is making waves within the industry to the intrigue of tape and wet sealant users alike. 

Product Comparisons
There are two major types of hot melts currently on the market: reactive and non-reactive. A reactive glazing product cures via a chemical reaction with moisture in the air at the time of application and allows for 3-5 minutes of open time. This process often results in off-gassing that requires heavily ventilated work areas or proper safety equipment for employees. 

Non-reactive products do not require moisture to cure, eliminating the need for added ventilation or breathing apparatuses for employees. They also extend glazing open time significantly while reducing operational costs for maintenance, waste and rejects.

Both reactive and non-reactive hot-melt glazing systems offer an immediate green strength that allows finished sashes to ship upon assembly. Some reactive hot melts do require lengthy curing times. And since hot-melt products do not require finished storage, inventory concerns are a thing of the past. 

Hot-Melt is Becoming Product of Choice
Some window and door manufacturers view the switch to hot-melt products as an added expense due to the need for glazing tables and pumps in the automation process. However, the transition is actually about moving from manual application into automation–a step that has proven to increase productivity. It is estimated that hot-melt products already represent approximately 10 percent of the glazing market with continued growth anticipated. 

In the end, the best protection against increased overseas imports is the use of materials that diminish labor costs, byproduct disposal and the curing process. It is also important that glazing/bedding materials offer immediate green strength without seal imperfections or the need for added floor space. Hot-melt glazing systems provide all of these qualities and allow finished sashes to be delivered faster than other methods. 

Mark Smith serves as marketing manager for Q’So Inc. in Saginaw, Texas

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