An air drying primer supplied as a dilute solution of moisture-reactive materials in volatile siloxane is used to improve both the quality and speed of adhesion development to room temperature vulcanizing silicone sealants to a variety of common non-porous substrates.

• Improves adhesion of silicone sealants to many substrates
• Provides more uniform and stronger bonds
• Conforms to South Coast and Bay Air Quality Management District Regulations for architectural sealant primers
• Low VOC at 76 g/l
• Formulated for low toxicity
• OS solvent used does not deplete the ozone layer. OS = Ozone Safe
• Primer is suitable for weather sealing and structural glazing applications

DOWSIL™ 1200 OS Primer is used to improve adhesion and accelerate adhesion build-up of silicone sealants to various substrates. This moisture-curing primer is supplied as a dilute solution of reactive materials in low-viscosity siloxane. The DOWSIL™ 1200 OS Primer is classified as Low-Solids Adhesive Primer according to the following regulations: Rule 1168 for Adhesives and Sealant Applications published on the South Coast Air Quality Management District and Rule 8-51 for Organic Compounds, Adhesive and Sealant Products published by the Bay Area Air Quality Management District. The VOC Inclusive value reported on the product label follows the definitions on these regulations. The VOC Exclusive value on the product label does not apply

Application
Primer for silicone adhesives and sealants

Direction to Use
With many surfaces, substantially stronger and more uniform bonds are obtained by preparing them with a primer prior to the application of the silicone sealant. For obtaining best results, the following steps should be followed on all surfaces except silicone rubber. 1. Thoroughly clean and degrease the surface using a 2 rag wipe method and appropriate solvent, when needed. Cleaning procedures are defined in the Americas Technical Manual. Allow the surface to dry. 2. Apply a thin coat of DOWSIL™ 1200 OS Primer by applying with a clean white rag or brush. In most cases, a thin primer film will give best adhesion. If a white chalky residue is noticed after several minutes of drying time, wipe away the chalky residue with a clean rag. 3. At normal temperatures and humidity conditions (room temperature, 50% R.H.), the primer should be allowed to air dry from 15 to 90 minutes. Because the primer cures in contact to air moisture, low humidity will necessitate longer drying time. The optimal drying time for a specific area should be determined prior to use. Primer which is allowed to cure extensively will not promote adhesion anymore. As a general rule, drying times of more than 6 hours at normal temperatures and humidity should be avoided. 4. Apply silicone sealant.