Sealants Technology
At the Heart of the Installation Quality Issue

by Carl Wagus

The sealants arena is arguably the heart and soul of installation. 
Industry task groups currently are engaged in what is “probably the largest sealant activity outside of ASTM,” according to AAMA sealants committee chairperson Ron Gzell of Schnee-Morehead Inc.

“ASTM doesn’t always cover the newer materials, so we are taking 
the lead in addressing what can be used in different situations with varying performance challenges,” said Gzell. “Insurance companies faced with coverage liabilities for product leakage are certainly interested, and there are implications for evolving the content of the InstallationMasters program.”

An easily overlooked consideration is how a single-minded focus on sealing against leakage can affect other window performance aspects.

For example, expanding foam air seals are being examined with the intent of writing a new specification. Extensive testing commissioned by AAMA is aimed at quantifying the degree to which expandable foam sealant exerts pressure on window framing members as it cures, pressure that can lead to frame distortion and hamper sash operation. The aim is to develop reliable expansion pressure ratings for various foam sealant products, which a window manufacturer can use to predict the effect on a given window design accurately. In particular, the resulting new specification for foam pressure ratings will assist manufacturers in recommending the use of newer foams confidently, designed specifically for window installation rather than general use. 

Tapes, Adhesives and Flashing
The performance of low-pressure pre-compressed cellular tapes, a technology widely used in Europe, will also be quantified in a new specification. These tape products, an alternative to expanding foam seals, will be characterized similarly in terms of pressure build to facilitate its use in the U.S. market. 

Self-adhering flashing, another focus of leak prevention, is the subject of yet another new performance standard that will encompass test methods for “Type A” products (materials that do not need primer) and “Type B” (materials that require primer to meet the requirements). Performance in terms of peel strength on 3.3 ply OSB is expected to form the basis for the specification. 

The performance of adhesives for attaching simulated divided lite muntin bars also will be quantified in a new specification under development. 

In addition, existing specifications–as always–have to be updated to reflect new technologies and new performance requirements. Accordingly, the venerable AAMA 800-92 sealants specification is undergoing a significant revamp. The allied Fenestration Sealants Guide Manual (AAMA 850) and the Joint Seals volume (JS-91) of the Curtainwall Manual series are also being upgraded to eliminate obsolete methods and accommodate newer types of products.

Some notable elements of this effort focus on gunnable back bedding, gunnable sealants and expanded cellular tape.

In the former, adhesion performance test procedures are being changed from the highly subjective peel test to a new lap shear test. Work is progressing now to define several different conditioning exposures based on a faster-curing (½-inch versus 1-inch) overlap.

Gunnable sealant performance standards will be separated and updated for newly defined “Type 3” (curing) and “Type 4” (non-curing) sealants. For example, curing sealants will be categorized by weight loss and addressed in the weatherability/durability portion of the specification. 

The expanded cellular tape specification is being augmented by addressing pre-formed cellular perimeter seals, with testing protocols now under development.

This collection of testing and specification development activity should result in significant tools for manufacturers to reference when called upon to justify their product designs and, more importantly, their installation practices and recommendations.