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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
Condensation Cure Systems
MESIL® OH polymers are the structural backbone for RTV systems. During the compounding stage, terminal silanol groups react with excess multi-functional silanes, creating a moisture-curable network for electronics, automobiles, and building materials.
Textile Finishing
Middle viscosity grades react with active sites on fiber surfaces. This forms a wash-resistant, soft-touch network that provides fabric durability without compromising breathability.
Frequently Asked Questions
+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.