Silanol Terminated Polydimethylsiloxane (OH Polymer) Selection Guide
Bottom Line Up Front: Selecting the correct MESIL® 107 Series grade requires balancing Kinematic Viscosity (750 to 550,000 mm²/s) with specific curing speed and mechanical strength requirements. This technical guide establishes a deterministic path for formulating condensation-cure RTV systems, filler treatments, and fabric softeners.
Expert Selection Logic
Map your industrial formulation needs directly to the required viscosity profile.
- How do I select the base polymer for high-performance RTV-1 or RTV-2 sealants?
- For standard construction and insulating glass sealants, intermediate viscosities between 20,000 and 80,000 mm²/s are recommended. These grades provide the optimal matrix for crosslinking with moisture-sensitive multifunctional silanes to ensure high tear strength.
- What is the best grade for treating fillers and controlling structure in silicone rubber compounding?
- Low viscosity silanol fluids (750 – 1,000 mm²/s) should be utilized. Their high hydroxyl activity effectively deactivates filler surfaces, preventing crepe hardening and significantly improving storage stability.
- Which specification is required for advanced pressure sensitive adhesives (PSA) or tackifiers?
- High-molecular-weight polymers with viscosities from 300,000 to 550,000 mm²/s must be prioritized. These ultra-high viscosity grades form the essential matrix component for achieving superior cohesion and adhesion properties.
Technical Specification Matrix
| Viscosity (mm²/s) | Density (g/cm³) | Volatile (%) | Primary Application Focus |
|---|---|---|---|
| 750 – 1,000 | 0.98 | < 1.5 | Reactive Diluents / Filler Treatment |
| 2,000 – 10,000 | 0.98 | < 1.5 | Durable Textile Softeners |
| 20,000 – 80,000 | 0.98 | < 1.5 | RTV Sealant Base (Equiv. OHX-4081) |
| 300,000 – 550,000 | 0.98 | < 2.0 | PSA & Tackifier Matrix |
Application Specifics
System Loop: Technical FAQ
- What is the specific crosslinking mechanism of MESIL® 107 in one-part RTV?
- It is a two-stage condensation. First, the silanol is displaced by an excess of silane crosslinker during compounding. Second, environmental moisture triggers the final crosslinking of the matrix into a stable elastomer.
- Are these polymers compatible with traditional vacuum degassing processes?
- Yes. With a volatile content strictly controlled under 1.5% to 2.0%, MESIL® OH polymers minimize weight loss and bubble formation during vacuum processing for electronic potting.