MS sealant (silane-modified polyether sealant) is an advanced, high-performance, eco-friendly elastic sealing material based on silane-terminated polyether that cures via moisture. Its solvent-free formulation, excellent adhesion, outstanding weather resistance, paintability, and stress-relief capabilities make it widely used in construction, industrial, and transportation applications, gradually supplanting traditional silicone and polyurethane sealants.
1. Composition and Formulation
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MS Prepolymer (Silane-terminated Polyether): A uniform, stable poly(propylene oxide) backbone providing elasticity.
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Fillers: e.g., fumed silica to enhance mechanical strength and adjust rheology.
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Plasticizers (e.g., DOP, DCPP, DBP): Lower hardness and boost elongation, though excess can impair sag resistance and mechanical properties.
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Silane Coupling Agents: Promote crosslinking, strengthen chemical bonding with substrates, and integrate into the curing network.
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Catalysts: Primarily organotin compounds (e.g., tin octoate, dibutyltin dilaurate) or tertiary amines to control cure rate and shelf stability.
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Anti-aging Additives (UV absorbers, light stabilizers, antioxidants) and Moisture Scavengers (e.g., vinyl trimethoxysilane) ensure long-term weather resistance and storage stability.
2. Curing Mechanism
MS sealant cures by moisture-triggered crosslinking: its alkoxy silane end groups react with atmospheric water, releasing alcohol byproducts and forming Si–O–Si bonds. This builds a three-dimensional, flexible polyether network.
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Tack-free time: ~20–30 minutes; full cure: 2–3 days (23 °C, 50% RH).
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Service temperature: –40 °C to +100 °C (or higher), with minimal shrinkage post-cure.
3. Performance Characteristics
| Property | Description |
|---|---|
| Environmental Safety | Solvent-free, isocyanate-free, ultra-low VOC; no irritating odor before cure. |
| Adhesion | Bonds strongly to glass, aluminum, stone, concrete, plastics, etc., without primer. |
| Weather Resistance | Excellent water resistance, UV stability, and aging resistance; resists cracking and yellowing. |
| Paintability | Can be over-coated directly with water- or solvent-based paints, enabling seamless finishes. |
| Stress Relief | Low modulus and high elongation absorb joint movement from thermal expansion, settlement, wind. |
| Workability | Smooth extrusion, thixotropic behavior, and flexibility down to 4 °C; workable up to 40 °C. |
4. Major Applications
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Construction: Curtain walls, window frames, decorative joints, waterproofing, and structural reinforcement.
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Transportation: Sealing and bonding in buses, high-speed trains, and vehicle bodies—metal to plastic—without primer.
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Industrial Manufacturing: Automotive assembly, rail transit, containers, elevators, marine equipment, HVAC systems.
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Renewable Energy: Solar module bonding and encapsulation—rapid cure increases manufacturing throughput.
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Appliances & Residential: Mold-resistant sealing in kitchens and bathrooms; bonding of mirrors, light fixtures, decorative trims.
5. International Standards & Certifications
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EN 15651-1 F-EXT-INT-CC: Non-structural sealants for façade and interior with low temperature performance.
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ISO 11600: Sealant classification by performance; typical grade: 25 LM (low modulus).
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JC/T 485-2007 & GB/T 14683-2016: Chinese standards classifying MS as modified silicone polymer.
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ASTM C920, AAMA, UL: Many MS sealants meet or can be certified to these international requirements.
6. Comparison with Traditional Sealants
| Feature | MS Sealant | Silicone Sealant | Polyurethane Sealant |
|---|---|---|---|
| VOC Level | Ultra-low (A+ grade) | Low–medium | High |
| Primer Required | None | None | Often required |
| Weatherability | Excellent | Good | Fair |
| Paintability | Directly paintable | Not paintable | Partially, needs tests |
| Elastic Recovery | > 70% | ≤ 50% | ~ 60% |
| Substrate Safety | Non-corrosive | Non-corrosive | May corrode some metals |
MS sealant surpasses or complements silicone and polyurethane types in environmental impact, overall performance, and application versatility, aligning with modern green building and advanced industrial demands.
