U-Seal 816 | One-part polyurethane self-levelling sealant, bubble-free curing

U-Seal 816 is a one-component polyurethane construction sealant that is easy to apply and non-sagging. It cures upon exposure to moisture in the air, forming a high-performance compound with permanent elasticity and excellent resistance to aging and weather conditions.

• One-component – no on-site mixing required.
• Self-leveling consistency.
• Cures without air bubbles.
• Non-staining.
• Resistant to hydrocarbons, oils, and fuels. Bitumen-free.
• Excellent adhesion to concrete without the need for primer.
• Permanent elasticity; accommodates joint movement up to ±25%.
• Highly resistant to aging, weathering, detergents, seawater, and limewater.

Application

U-Seal 816 is a versatile, high-performance construction sealant for expansion and construction joints in both vertical and horizontal applications, including joints in prefabricated elements, exterior wall joints, and cladding joints.

U-Seal 816 is suitable for sealing metal roofs and gutters, bridge and balcony railings, waterproofing joints between tiles, blocks, masonry, wood, concrete, metal, window or door frames, joints in water channels, and for general hydraulic sealing applications exposed to water.

Certifications

Technical Data

Property	Value/Description
Appearance	Non-sag thixotropic paste
Color	White, Grey, Black (Other colors available on request)
Chemical Nature	Polyurethane
Curing Mechanism	Moisture-curing
Curing Through Volume (NPT Method 07)	ca. 2 mm (24h at 23°C and 50% RH)
Hardness Shore A (DIN 53505)	ca. 30
Density (NPT Method 06)	ca. 1.34 g/cm³ (23°C and 50% RH)
Skin Time (NPT Method 17)	ca. 120 min (23°C and 50% RH)
Elastic Modulus at 100% (ISO 37 DIN 53504)	ca. 0.4 N/mm²
Tensile Strength (ISO 37 DIN 53504)	ca. 1.5 N/mm²
Elongation at Break (ISO 37 DIN 53504)	ca. 750%
Joint Movement Capability (ASTM C920)	±50% of joint width
Application Temperature	From +5°C to +40°C
Temperature Resistance	From -40°C to +100°C

Datasheet

U-Seal 816 Datasheet

Instructions for Use

The surface to be treated must be completely clean, dry, and free of dust or grease. U-Seal 816 T exhibits excellent adhesion without the need for a primer on most common construction materials. Therefore, if the surface is properly prepared and reinforced, primer is not required. However, tiles, natural stone, plastics, paints, coatings, and other treatments may present adhesion challenges. Thus, preliminary testing is recommended.

The optimal application temperature is between 15° and 25°C. For easier application in cold weather, it is advised to store the material at approximately 25°C before use. To ensure the sealant moves freely within the joints, it is important that the sealant does not adhere to the bottom of the joint. Therefore, to create a proper joint, an airtight polyethylene backer rod should be placed at the correct depth.

If necessary, apply a suitable primer to the sides of the joint and allow appropriate waiting time to avoid solvent entrapment, which could cause air bubbles in the uncured sealant under rising temperatures. For the best performance, the sealant should be injected into the joint when the gap is at its midpoint between expansion and contraction as designed. Apply the sealant firmly into the joint to ensure full contact with the sides of the joint and the backer rod at the bottom. Keep the nozzle within the sealant, and maintain a steady flow to avoid air entrapment. Avoid overlapping the sealant to eliminate the risk of air pockets.

Finishing and smoothing must be completed during the sealant’s tack-free time. U-Seal 816 can be overpainted. Paint compatibility should be tested by conducting preliminary tests. Care should be taken when using alcohol or alkyd resins, as these may affect the curing process and extend the drying time of the paint. Paint hardness and thickness can impair the sealant’s elasticity, potentially leading to paint film cracking.

Do not allow the sealant to cure in the presence of other curing silicone sealants. Avoid exposure to solvent-based cleaners during the curing process. When applying the sealant, avoid air entrapment. As this is a moisture-curing system, sufficient air exposure is required.

Cleaning Instructions

Clean tools with acetone or solvent. Uncured sealant can be removed with paper or cloth. Once cured, the product can only be removed mechanically. Avoid skin contact by using latex, rubber, or polyethylene gloves. In case of skin contact, remove immediately and wash thoroughly with soap and water.

Storage Instructions

U-Seal 816 can be stored for 12 months in its original (unopened) packaging at temperatures between 10°C and 25°C in a dry, cool place. Storage temperatures should not exceed 25°C for prolonged periods. Avoid storing in humid areas, direct sunlight, or near heat sources.