2K Epoxy, PU or MS Polymer - which adhesive?
Structural adhesives carry load-bearing forces and often replace screws or welds. This guide compares 2K epoxy, polyurethane and MS polymer by lap-shear strength, gap filling and temperature and media resistance so you can pick the right system with confidence.
View structural adhesivesWhat defines a structural adhesive?
A structural adhesive transfers load-bearing forces permanently and is judged by its lap-shear strength, elasticity and resistance. The three key chemistries are rigid 2K epoxy, tough-elastic polyurethane (PU) and flexible MS polymer. The stiffer the bond line, the higher the strength but the lower its ability to absorb strain and vibration.
The choice therefore follows the whole load profile, not just peak strength: static load, thermal expansion of dissimilar materials, vibration and media contact. A rigid adhesive transfers point loads, a flexible one spreads stress across the area.
- Rigid (2K epoxy): highest strength, low elongation, more brittle under impact.
- Tough (PU): good strength with toughness, handles shock and vibration.
- Flexible (MS polymer): lower strength, high elongation, absorbs movement.
2K epoxy, PU or MS polymer side by side?
The overview below shows typical values. Lap-shear strength is tested to DIN EN 1465; the figures apply to cleaned, well-prepared metal surfaces.
2K epoxy leads on pure strength but tolerates little strain. PU delivers a balanced mix of strength and toughness. MS polymer scores with high elasticity, large gap filling and moisture resistance, without isocyanates and usually without a primer.
How do they handle temperature and chemicals?
Beyond strength, resistance decides service life. 2K epoxy is chemically very robust against oils, fuels and many solvents but only tolerates constant moisture to a limited degree. PU is tough and impact-resistant but ages faster under UV. MS polymer is highly weather- and UV-stable and insensitive to moisture, but stands up less well to solvents.
- Oil, fuel, solvents: 2K epoxy is the first choice.
- Constant moisture, outdoors, UV: prefer MS polymer.
- Impact, vibration, cold environment: PU handles dynamic load best.
- High temperature above 120 °C: check special heat-curing epoxies.
Where sealing matters more than load transfer, look at dedicated sealants.
Read the guideFrequently asked questions
Which adhesive has the highest strength?
2K epoxy reaches the highest values at 15 to 30 MPa lap-shear strength and suits stiff, load-bearing joints between similar materials.
When is MS polymer the better choice?
For flexible joints with thermal expansion, large gaps up to 5 mm and moisture or UV exposure outdoors, where movement has to be absorbed.
How much gap can a structural adhesive fill?
2K epoxy fills roughly 0.1 to 2 mm, PU up to about 3 mm and MS polymer up to about 5 mm. Larger gaps need flexible systems with high non-slump behaviour.
Do you always need a primer?
Not always. Degreasing and abrading are decisive. On critical substrates such as some plastics or for constant moisture, a matching primer clearly improves durability.
Find the right structural adhesive?
We stock 2K epoxies, polyurethane and MS polymer adhesives including primers and accessories - matched to strength, gap and media resistance.
Tested values
Strength documented to DIN EN 1465.
For every load
Rigid, tough or flexible for the job.
Durable
Systems for temperature, moisture and media.
Expert advice
Our specialists help you choose.