18/05/2021
Sealants play a pivotal role in adding to glass capabilities and can provide added strength and value to complex glass creations. Structural silicone glazing is a technique of attaching glass to a metal frame using structural silicone sealants and gives the architectural design freedom for commercial building structures. However, choosing the right sealant and ensuring compatibility can affect the total outcome of the structural glazing system.
Structural Sealant Glazing | Complexity of Details
Looking at this diagram, you can see there are several components within the design of a structural glazing (SG) system and it is critical that all these elements are compatible to ensure the long-term durability of a structurally glazed façade.
Acid curing silicones must not be used in structural glazing applications as the liberated acid can be corrosive to metallic bonding substrates.
Some sealants, gaskets and other accessories may contain fluids or plasticisers that could potentially migrate through into the structural and insulated glazing sealant. This must be prevented as they could significantly impact the performance of these products.
See photographs below on compatibility for non-approved EPDM profiles which show migration of organic plasticiser into the structural silicone sealant. The discolouration is the result of the ultra-violet radiation used in the test decomposing the organic plasticiser. The level of fluid migration will result in the intensity of the discolouration of sealant. This could affect the mechanical properties and adhesion of the structural sealant depending on the type and quantity of the fluid.
Structural Sealant Glazing | Lab Tests-Compatibility
Influence of non-approved EPDM profiles | Influence of non-approved weather sealants (organic plasticizer)
1|Discolouration
ASTM C1087
2|Deviated Mechanical Properties
ETAG 002
3|Adhesion Problems
ETAG 002
ASTM C1087
Structural Sealant Glazing | Incompatibility with EDPM Gasket
After only 6 months: Disintegration of IG units
In this picture the installer changed the approved gasket for a cheaper lower cost product. No test was undertaken and fluid from this gasket migrated through the secondary sealant of the insulated glass unit and dissolved the PIB primary butyl seal. This resulted in all the insulated glass units having to be replaced on the project at a significant cost.
Setting Blocks
PE, Nylon, uPVC and Silicone that do not contain any fluid or plasticiser are suitable for use in structural glazing projects.
Backer Rods
Closed-cell PE or open-cell have no known compatibility problems. If the polyethylene backer rod is damaged or punctured it should be left approximately 30 minutes, this allows for trapped gas within the backer rod to dissipate.
Spacer Tapes
Open-cell Polyurethane Spacer Tapers such as Sika® Spacer Tape HD or Norton V2100 tape can be used without testing.
Becoming a Sika Bonding Excellence Contractor and the Benefits
To request an informative webinar on the Sika Bonding Excellence Platform please click the button below for further information.
As a Bonding Excellence Platinum Contractor, Sika will promote and support you in all your structural glazing projects.
Sika Here to Support You All the Way!
Sika carry can out compatibility tests for you as part of your project-specific testing as part of the Sika Bonding Excellence Platform
For further information and advice please complete the below for to contact Andrew Hills | National Key Account Manager for Facades Fenestration Insulated Glass
Written by Andrew Hills|National KAM for Sika FFI and Jeff Richards|Business Development Manager
