CRL Polyurethane Construction Sealant Cartridge - Limestone Smooth

• One-part smooth-finish modified polyurethane sealant with primerless adhesion on most common construction surfaces, including KYNAR® coated metals (SKU: M64L)
• AAMA approved
• VOC compliant — only 9 g/L
• UV resistant / non-yellowing

CRL M64 is a one-part, moisture-curing, gun-grade modified polyurethane construction sealant (M64L). It provides durable, permanently flexible performance for moving joints and typically does not require primer on common substrates. Designed for exterior and interior use, M64 resists UV yellowing and withstands service temperatures from -75°F to 300°F (-59 to 149°C). It skins over in ~30 minutes and cures at approximately 1/8" (3 mm) per day.


Basic uses
CRL M64 Modified Polyurethane Construction Sealant is formulated for sealing moving perimeter joints in concrete, masonry, metal, and typical storefront and curtain wall framing-to-structure joints. It bonds to fluoropolymer metal coatings such as KYNAR®, Duranar®, and Duranar® Sunstorm™, plus standard metals (aluminum, steel, galvanized steel), plastics, vinyl, glass, wood, concrete, brass, and other common substrates. Compatible with insulating glass sealants for toe or heel beads and suitable for manufacturing applications (e.g., travel trailers, mobile homes) and assembly of galvanized HVAC ductwork. Paintable after two hours with water-based paints.

Features
- Exceptional adhesion to KYNAR® coated metals and other fluoropolymer finishes.
- Low-VOC, solvent-free, isocyanate-free formula — only 9 g/L (chemically curing < 3%).
- Qualifies for LEED credit (EQ Indoor Environmental Quality); USDA approved for meat and poultry areas.
- Permanently flexible — resists hardening with age and remains flexible at low temperatures.
- Low-temperature gunning and application above 0°F (-18°C).
- Fast cure: skins in ~30 minutes; tooling time ~20–40 minutes depending on conditions.
- Paintable with water-based paints after 2 hours.
- UV resistant — will not yellow from sun exposure.

Technical data & approvals
CRL M64 conforms to Federal Specification TT-S-00230C Type II Class A and ASTM C920-98 Type S, Grade NS, Class 25 (Use NT, M, T, A, G, and O). Also meets numerous ASTM standards and CAN/CGSB-19,13-M87 (QPL #81026), AAMA 808.3-92 exterior perimeter and AAMA 802.3-92 Type II ductile back bedding compound. Meets CARB 2003 VOC requirements and qualifies for LEED® credits.

Limitations
Do not apply over damp or contaminated surfaces. Use