Joint Sealants can be broken down into six primary categories:
- Acrylics
- Butyls
- Latex
- Polysulfides
- Polyurethanes (PU)
- Silicones
- Silyl Modified Polymers (SMP)
1. Acrylics (solvent-based) Paint
- 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
2. Butyls (solvent-based)
- 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
3. Latex (water-based, including EVA, acrylic – also known as "caulk")
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
4. Polysulfides
- 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
5. Polyurethanes (PU)
- 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
6. Silicones
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
7. Silyl Modified Polymers (SMP)
- 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