Sealant Compatibility: Application, Material and Testing Considerations

Sealant compatibility doesn’t just refer to adhesion. Testing for sealant compatibility means determining if two materials can co-exist without detrimental effects such as discoloration, material degradation or adhesion loss. There are some applications and material combinations that architects, fabricators and glazing contractors should keep in mind when considering compatibility.

Testing Explained

It’s important to ensure that glazing system components such as gaskets, setting blocks, spacers and shims won’t create negative outcomes due to interaction with the sealant. Adam Milter, technical application specialist, sealants and glazing for Tremco Commercial Sealants & Waterproofing of Beachwood, Ohio, says sealants can also interact with coatings and interlayers.

“If using an insulating glass system, we test the sealant on the insulating glass itself and the secondary seal,” he says.

Sealant compatibility testing to ASTM C1087-16, Standard Test Method for Determining Compatibility of Liquid-Applied Sealants with Accessories Used in Structural Glazing Systems, can take up to 28 days. It requires samples of components such as gaskets and setting blocks be sent to the sealant manufacturer for a compatibility evaluation.

“Experience has shown that testing will reveal any or most compatibility issues that may present themselves in the sealant over time,” says Milter, who explains that the testing process typically happens once the sealant and accessories have been identified.

Jon Kimberlain, senior technical service and development scientist for Dow Performance Silicones of Elizabethtown, Ky., says Dow recommends testing for structural glass projects, even if a configuration has been tested for a past project.

“For structural there are very specific requirements for the warranty from a sealant manufacturer specific to a project,” he says. “There can sometimes be variability. There are situations where people have submitted a material and it looked great with no issues but when they go and buy the material they see discoloration. This may be the result of submitting something different from what they ended up buying.”

Interlayer Compatibility

In some laminated glass applications, a plasticizer can migrate from the interlayer or sealant to the other, causing discoloration or delamination. Florian Doebbel, business development manager of façades, for Sika of Lakewood, N.J., says this issue is becoming more critical in applications such as glass railings where laminated glass is required to meet the current version of the International Building Code.

Previously, tempered glass alone could be used in frameless railing applications where the glass is fixed in a base shoe. Now laminated safety glass must be used.

“Those installers have to deal with interlayer compatibility,” he says. “I’ve heard from customers that it’s the same with glass doors that are just retained at the top and bottom.

Doebbel says sealants and grout can come into contact with the laminated glass edge, which can cause damage or creeping. If any of the materials are degraded, the system could fail to protect the glass from water, which could cause further damage.

Applications and Materials

Milter says that EPDM rubber and neoprene have more of a tendency to show compatibility issues when tested against silicone sealants but there also have been instances where those materials have been tested with silicone sealants and showed no issues.

Kimberlain says compatibility is especially important in four-sided structural glazing applications. He explains that if the setting blocks used are made of natural rubber with plasticizers, that these plasticizers can migrate through the sealant and turn brown due to sun exposure.

Compatibility testing is also important when companies are innovating or using a unique combination of materials. “There might be an interaction you weren’t even aware of because you’re combining materials in a way that’s unique,” says Kimberlain.

Jordan Scott is an assistant editor for USGlass magazine. She can be reached at

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