Silicone, polyurethane or MS polymer - which sealant?
Silicone, polyurethane (PU) and MS polymer cover different sealing jobs. This guide separates the three chemistries by paintability, UV and temperature resistance and adhesion, and shows which sealant suits which joint.
View sealantsSilicone, PU or MS polymer - what is the difference?
Sealants differ mainly in their base chemistry. Silicone usually cures with humidity and stays permanently elastic, polyurethane (PU) is mechanically strong and paintable, and MS polymer (silane-modified polymer) combines the best of both without isocyanates or solvents.
The right choice comes down to four questions: Does the joint need painting? Is it exposed to constant UV? What temperatures occur? And on which substrate must the sealant hold? Clarify these and you can separate the three chemistries with confidence.
- Silicone: permanently elastic, heat and UV resistant, but not paintable.
- Polyurethane: high strength, paintable, sandable, less UV stable.
- MS polymer: paintable, low odour, adheres to many substrates without primer.
Paintability, UV and temperature compared
The four core criteria can be set side by side. Silicone wins on temperature and UV, PU and MS polymer on paintability and finishing. That way every sealing job finds its chemistry.
Which sealant for which joint?
The application dictates the chemistry. Sanitary and glass joints call for permanently elastic, mould-resistant silicone, while load-bearing or painted connections favour PU or MS polymer. When in doubt, MS polymer is the safe all-rounder.
- Bathroom, kitchen, glass and sanitary: neutral-cure silicone with fungicide.
- Expansion joints and painted connections: polyurethane or MS polymer.
- Metal, vehicle and body construction: MS polymer, isocyanate- and solvent-free.
- High temperature (chimney, oven, exhaust): special silicone up to +300 °C.
- Always prepare substrates clean, dry and free of grease.
Frequently asked questions
Can you paint over silicone?
No. Paint does not bond durably to silicone and peels off. Where a joint must be painted, PU or MS polymer are the right choice.
Is MS polymer better than silicone?
It depends on the job. MS polymer is paintable, low-odour and broadly adhesive, while silicone handles heat and UV better and suits permanently wet joints such as in bathrooms.
Which sealant withstands heat?
Standard silicone lasts from -40 to +180 °C, special silicone up to around +300 °C. PU and MS polymer sit near +90 °C continuous service temperature.
Do I need a primer?
MS polymer adheres to many substrates without a primer. Silicone and PU, and difficult materials such as some plastics, often need a suitable primer.
Looking for the right sealant?
We supply silicone, polyurethane and MS polymer sealants for every joint - including matching primers and cartridge guns.
All three chemistries
Silicone, PU and MS polymer from one source.
Proven quality
Brand sealants with documented properties.
Matched to the joint
Paintable, UV-stable or heat resistant.
Expert advice
We help you choose by substrate.