Description
Sikasil® WS-305 CN is a neutral-cure silicone sealant with high movement capacity and excellent adhesion to a variety of substrates.
Product Benefits
- Meets ASTM C 920 (Class 50), TT-S00230C, TT-S001543A standards
- Exceptional UV and weather resistance
- Strong adhesion to various substrates, including concrete, glass, metals, coated and painted metals, plastics, and wood
Areas of Application
Sikasil® WS-305 CN is ideal for weatherproofing and sealing applications requiring durability in harsh conditions. It is particularly effective as a weather seal for curtain walls and windows.
Cure Mechanism
Sikasil® WS-305 CN cures through reaction with atmospheric moisture, beginning at the surface and progressing to the core of the joint. At lower temperatures, the curing process is slower due to reduced moisture content in the air.
Method of Application
Surface Preparation
Ensure surfaces are clean, dry, and free from grease, oil, and dust. Surface treatment is important for achieving a long-lasting bond.
Application
For optimal performance, the joint width should accommodate the sealant’s movement capability based on the expected joint movement. The minimum joint depth is 1/4″ (6 mm), with a width-to-depth ratio of 2:1. To avoid three-sided adhesion and to maximize the sealant’s movement capacity, use a compatible closed-cell polyethylene or non-outgassing polyolefin backer rod. If the joint is too shallow for backing material, use polyethylene tape as a bond breaker to allow the silicone to stretch freely.
Tooling and Finishing
Tooling and finishing should be done within the skin time of the sealant. Press the sealant into the joint bond line for effective adhesion.
Removal
Wash hands and exposed skin immediately with industrial hand cleaner and water; do not use solvents.
Overpainting
Sikasil® WS-305 CN cannot be painted over.
Application Limits
- Sikasil® WS-305 CN is compatible with most Sikasil® products. For information on compatibility with other Sikasil® sealants, consult Sika Technical Service.
- When using multiple reactive sealants, allow each to fully cure before applying the next.
- Sikasil® WS-305 CN should not be used on pre-stressed polyacrylate and polycarbonate elements, as it may cause environmental stress cracking.
- Test the compatibility of gaskets, backer rods, and other materials with Sikasil® WS-305 CN before use.
- Avoid joints deeper than 1/2″ (15 mm).
This information is for general guidance; specific application advice is available upon request.
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