Sealants compared: silicone, MS polymer, polyurethane, acrylic
Not all sealants are created equal. Silicone, MS polymer, polyurethane, and acrylic differ significantly in adhesion, elasticity, paintability, and durability. This comparison will help you choose the right material for your joint.
To the point: Which sealant is used for what?
Silicone: permanently elastic, temperature and weather resistant, but not paintable; ideal for sanitary applications, glass, and high temperatures. MS polymer: versatile all-rounder, adheres to many substrates, paintable, low odor. Polyurethane: tough, elastic, and abrasion-resistant for structural, stressed joints. Acrylic: paintable and economical for interior joints with minimal movement. The respective data sheets are binding.
The four families at a glance
| Characteristic | silicone | MS polymer | Polyurethan | Acrylic |
|---|---|---|---|---|
| elasticity | very high | high | high | small amount |
| Paintable | no | Yes | Yes | Yes |
| Adhesion without primer | medium | very good | good | medium |
| Weather/UV | very good | good | medium | small amount |
| Typical | Sanitaryware, glass, heat | universal, construction & industry | constructive, burdened | Interior joints, cracks |
These are guidelines; the specific suitability depends on the product and application and must be checked in the respective technical data sheet.
Selection by application
- Sanitary/Wet area: Silicone (sanitary, fungicidal).
- Universal bonding and sealing: MS polymer.
- Stressed, structural joints: polyurethane.
- Paintable interior joints: Acrylic.
- High temperatures/glass: Special silicone.
What matters
- Substrates and adhesion (primer needed?),
- Joint movement and required elasticity,
- Paintability
- Weather, UV radiation, temperature, media,
- Appearance and curing behavior.
Adhesion and primer
MS polymer and polyurethane adhere to many substrates often without a primer, silicone requires an adhesion promoter depending on the substrate, and acrylic is unsuitable for load-bearing bonds. For critical substrates, an adhesion test is necessary; values and primer recommendations can be found in the data sheet.
Inside or outside?
For exterior joints exposed to the elements, silicone and MS polymer are suitable thanks to their UV and weather resistance. Acrylic is appropriate for dry interior areas with minimal joint movement; polyurethane excels in structural, mechanically stressed joints.
Frequently Asked Questions
Which sealant can be painted over?
MS polymer, polyurethane and acrylic can be painted over, classic silicone cannot.
What holds up best in wet areas?
Sanitary silicone with fungicidal properties. Clean, dry surfaces and proper joint formation are essential.
Can I apply silicone over old silicone?
No, fresh silicone doesn't adhere well to old silicone. Completely remove the old sealant and degrease the area.
Sources and technical basis
The information is based on manufacturer data sheets and recognized principles of sealing and bonding technology. Adhesion, resistance, and suitability depend on the product and substrate and can be found in the respective technical data sheet.
How SILITECH supports
Describe the joint, substrates and load, we will recommend the appropriate sealant and provide the data sheets.
