Volume 34, Number 1, January 1999


IG Sealants for the Year 2000

by John Sands

With the millennium approaching we begin to wonder what new products and materials we will see enter our industry as we move into the 21st century. Based upon the myriad of new components, such as warm edge spacers and low-E coated glasses (which have become common place over the last decade), we can expect to see a continued influx of innovative, performance and production enhancing materials.

As is true for other components in the industry, sealants for the fabrication of insulating glass (IG) units are also evolving. In fact, we are currently experiencing the biggest wave of new materials to hit the glass and window business in 20 years. New single component curing sealants, which started to appear on the market approximately two years ago, are becoming more and more commonplace for a number of reasons. Improved performance of the insulating glass unit as well as convenience in application of the sealant are the most compelling reasons for the popularity of these products.

Dual Seal Equivalency

Construction of insulating glass units has traditionally fallen into several categories. Dual seal construction, using a polyisobutylene primary seal with a Permapol®, polysulphide, polyurethane, or silicone secondary seal, have been viewed as providing the best, most consistent performance. Other constructions including single seal Permapol, polysulphide, polyurethane, and hot melt butyl as well as Swiggle Seal® have also provided good results. The dual seal construction derives its advantage from the use of two sealants. The PIB (polisobutylene) primary seal acts as an excellent barrier to moisture and prevents the ingress of water vapor into the airspace as well as providing a soft cushion on the spacer shoulder. The secondary seal of Permapol or polyurethane provides high resistance to moisture but also provides the structural element of the dual-seal system. The strength of the sealant holds the lites of glass together and maintains the integrity of the PIB moisture barrier. The attributes of the two sealants in this system (PIB - moisture barrier, sealant – structural) each contribute in their own way to the excellent results achieved with dual-seal.

The new one-part curing materials combine the attributes of the dual seal components into one sealant. Products such as our PRC® 590, the first of these new products introduced to the market, provide moisture vapor transmission rates (MVTR) comparable to the moisture barrier component (PIB) of dual seal constructions. The strength of this product exceeds the structural rating of all of the conventional two-part sealants used as the secondary seal in dual seal construction (see chart page 48). As a result, the use of these new one-part products can provide performance equal to or better than conventional dual seal construction units. This fact has been demonstrated very dramatically by the excellent test results of this construction.

Performance Measurements

Dual seal units have gained a reputation as being superior performers not just based on the MVTR and structural ratings of their components but rather on their extensive and consistent field and test performance. Years of test results to the ASTM or the CGSB standard, combined with years of field performance, have confirmed the performance of dual seal construction. The dual seal equivalency concept should then be based on performance rather than just on the characteristics of the seal material. Test data from in-house testing, independent labs, and third party labs should be carefully scrutinized in evaluating these new products.

Other Parameters

Convenience of application is another criteria in evaluating sealant systems. Many of these new products have been directed at automated fabrication systems used in the manufacturing process. Because the sealant application is a continuous process, the right combination of tack and elasticity is required to maximize efficiency. Failure to provide the right characteristics to meet the needs of fabricators in these areas can impede manufacturing efficiency. Other considerations in selecting one of these new sealants are gas retention capabilities, compatibility with other components, such as spacer material or coated glass, and shelf-life issues.

The introduction of these new material types to the IG industry has provided the basis for improved unit and process performance. They have also laid the foundation for future generations of new sealant technology as we move into the new millennium.

John Sands is market manager for Courtaulds Aerospace, located in Glendale, CA. Courtaulds Aerospace manufactures insulating glass sealant products at its facilities in Gloucester City, NJ, and Shildon, UK.


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