Sikasil® WS-305 AM
Neutral-curing silicone weatherproofing sealant
Sikasil® WS-305 AM is a neutral curing silicone sealant with high movement capability and excellent adhesion to a wide range of substrates. It is particularly suited as a weather seal for curtain walls and windows. Sikasil® WS-305 AM is typically used for weathersealing curtain walls and glass butt joints or as a perimeter weather seal for windows, doors, and window walls. Further, the product properties of Sikasil® WS-305 AM are beneficial for field and shop applications related to rainscreen facades, prefabricated exterior wall systems and modular construction.
- Meets the requirements of ASTM C920 Type S, Grade NS, Class 50, Use NT, M,G,A
- Meets the requirements of ASTM C1184, Type S, Use G,A
- Meets the requirements of AAMA 803.3 and 808.3
- ASTM E84 with a Flame Spread Index of 15 (Class A acc. to IBC)
- Los Angeles Research Report (LARR) approved
- Good UV and weathering resistance
- Adheres well to many substrates including concrete, glass, metals, coated and painted metals, vinyl, and wood.
PRODUCT BENEFITS
- Meets the requirements of ASTM C920 Type S, Grade NS, Class 50, Use NT, M,G,A
- Meets the requirements of ASTM C1184, Type S, Use G,A
- Meets the requirements of AAMA 803.3 and 808.3
- ASTM E84 with a Flame Spread Index of 15 (Class A acc. to IBC)
- Los Angeles Research Report (LARR) approved
- Good UV and weathering resistance
- Adheres well to many substrates including concrete, glass, metals, coated and painted metals, vinyl, and wood.
Areas of Application
Sikasil® WS-305 AM can be used for weatherproofing and sealing applications where durability under severe conditions is required. This product is suitable for experienced professional users only. Testing with actual substrates and conditions should be performed to ensure adhesion and material compatibility.Product Details
| Chemical base | 1-component silicone | |
| Color (CQP001-1) | White, colonial white, black, bronze, medium bronze, aluminum, aluminum gray, anodized light gray, dark gray, gray S6 | |
| Cure mechanism | Moisture-curing | |
| Cure type | Neutral | |
| Density (uncured) | 1.40 kg/l | |
| Non-sag properties (CQP061-4 / ISO 7390) | 2 mm | |
| Application temperature | Ambient | 5 ─ 40 °C |
| Skin time (CQP019-1) | 50 minutes | |
| Tack free time (CQP019-3) | 130 minutes | |
| Curing speed (CQP049-1) | (see Diagram 1) | |
| Shore A hardness (CQP023-1 / ISO 48-4) | 20 | |
| Tensile strength (ASTM D412) | 1 MPa | |
| Elongation at break (ASTM D412) | 750 % | |
| Tear propagation resistance (CQP045-1 / ISO 34) | 4 N/mm | |
| Service temperature | -40 ─ 150 °C | |
| Shelf life | 12 months |
CURE MECHANISM
Sikasil® WS-305 AM cures by reaction with atmospheric moisture. At low temperatures the water content of the air is generally lower and the curing reaction proceeds some-what slower (see Diagram 1).
The curing speed of the reaction depends mainly on the relative humidity and temperature. Material temperature above 50 °C could lead to bubble formation and has to be avoided.
Diagram 1: Curing Speed of Sikasil® WS-305 AM
Application
METHOD OF APPLICATION
Surface preparation
Surfaces must be clean, dry and free from grease, oil and dust. Surface treatment depends on the specific nature of the substrates and is crucial for a long lasting bond. Sikasil® WS-305 AM is designed to obtain adhesion without the use of a primer however, certain substrates may require a primer. Test by applying the sealant and/or primer sealant combination to confirm results and proposed application methods.
Application
The optimum temperature for substrate and sealant is between 15 °C and 25 °C.
Sikasil® WS-305 AM can be processed with manual, pneumatic or electric driven piston guns as well as pump equipment. For advice on selecting and setting up a suitable pump system, contact the System Engineering Department of Sika Industry.
Joints must be properly dimensioned.
For optimum performance the joint width needs to be designed according to the movement capability of the sealant based on the actual expected movement. The minimum joint depth is 6 mm and a width / depth ratio of minimum 2 : 1 and maximum 4 : 1 must be respected.
Joints deeper than 15 mm must be avoided.
For backfilling it is recommended to use closed cell, sealant compatible foam backer rods e.g. high resilience polyethylene foam rod. If joints are too shallow for backing material to be employed, we recommend using a polyethylene tape. This acts as a release film (bond breaker), allowing the joint to move and the silicone to stretch freely.
Tooling and finishing
Tooling and finishing must be carried out within the skin time of the sealant or adhesive. When tooling freshly applied Sikasil® WS-305 AM press the adhesive to the joint flanks to get a good wetting of the bonding surface. No tooling agents to be used.
Removal
Uncured Sikasil® WS-305 AM can be removed from tools and equipment with Sika® Remover-208 or another suitable solvent. Once cured, the material can only be removed mechanically.
Hands and exposed skin have to be washed immediately using hand wipes such as Sika® Cleaner-350H or a suitable industrial hand cleaner and water.
Do not use solvents on skin.
Overpainting
Sikasil® WS-305 AM cannot be overpainted.
Application limits
- Due to staining, Sikasil® WS-305 AM is not recommended for use on natural stone such as marble, granite, quartzite, etc.
- Most Sikasil® WS, SG, IG and WT, silicones manufactured by Sika are compatible with each other and with SikaForce® products.
- For specific information regarding compatibility between various Sikasil® and SikaForce® products contact the Technical Department of Sika Industry.
- To exclude materials influencing Sikasil® WS-305 AM, all materials such as gaskets, tapes, setting blocks, sealants, etc., in direct and indirect contact have to be approved by Sika in advance.
- Where two or more different reactive sealants are used, allow the first to cure completely before applying the next. Sikasil® WS-305 AM may only be used in combination with structural glazing applications after a detailed examination of the corresponding project details.
- Do not use Sikasil® WS-305 AM on PMMA and PC elements as it may cause environmental stress cracking (crazing).