Sealant Chemistries

Joint Sealants can be broken down into six primary categories:

Used in residential and light commercial construction, mainly for exterior applications
Generally meet ± 12.5% movement (ASTM C 920, Class 12-1/2)
May need special handling for flammability and regulatory compliance
Can be painted
Short open time; difficult to tool
Exhibit some shrinkage upon cure
Often used for perimeter sealing and low movement joints

Excellent adhesion to most substrates
Excellent water vapor transmission resistance
Limited movement capabilities, generally up to ± 10%
Excellent weathering
Sometimes used in curtain wall applications where adhesion to rubber compounds is needed
Most are stringy and difficult to apply neatly
May show some shrinkage after cure; may harden and crack over time on exposed surfaces
Some are not suitable for application where exposed to UV
Some are non-hardening and are suitable for concealed application where sealant needs to remain pliable

Courtesy AlbionUsed mainly in residential and light commercial construction applications
Interior and exterior use
Premium products meet ± 25% movement (ASTM C 920, Class 25)
Excellent paintability (with latex paints)
Very good exterior durability
Exhibit some shrinkage after cure
Not used for exterior applications, particularly on high rise construction, for applications undergoing significant cyclic movement, or for high-profile structures

First “high performance” sealant; mainly used in industrial applications (ASTM C920, Class 12-1/2 or 25)
Poor recovery limits their use in joints with high cyclic movements
Can be formulated for excellent chemical resistance (especially for aviation fuel)
Good performance in submerged applications
Require a primer on almost all substrates

Used in industrial and commercial applications
Very good movement capabilities, up to ± 50% (ASTM C 920, Class 25 and 50).
Not used in SSG applications (avoid direct contact to glass)
Excellent bonding, generally without a primer for many surfaces
Can be formulated for good UV resistance, which may be compromised by a selected color
Paintable
Some formulations may contain low levels of solvent

Picture of a NY Condo built using silicones Structural bonding and structural sealant glazing (SSG) of glass to frames
Excellent joint movement capabilities; can exceed ± 50% (ASTM C 920, Class 50 and Class 100/50)
Excellent low temperature movement capability
Excellent UV and heat stability
Good adhesion for many substrates especially glass; a primer is recommended on certain substrates, particularly porous substrates
Not paintable
Used in protective glazing systems and insulating glass units to improve thermal performance (reduce heat loss). Also used for missile impact and bomb blast situations
Acetoxy chemistry based sealants have strong odor, but newer chemistries have very low odor
Adhesion, as for all sealant types, is adversely affected by less than perfect application conditions
High, medium and low modulus sealants available
May stain some types of natural stone without primers. Low staining potential formulations are available

One of the newest sealant technologies
Enable broad use in construction, industrial, DIY, automotive, marine and transportation markets (not recommended for structural sealant glazing applications)
Excellent adhesion and movement capabilities; good UV and heat stability
Paintable
Provide exceptional bonding to plastics, metals, wood and stone
Can exceed ± 50% joint movement capability (ASTM C 920) even in low temperatures
Contain no solvent, contribute less VOC, and yield lower odors compared to other chemistries

Adhesives & Sealants