The best of polyurethanes and silicones - Silane terminated prepolymers (STP) – Desmoseal® S

Silane-terminated polymers (STP) under the trade name Desmoseal® S represent the youngest product generation of polymers for moisture curing elastic adhesives and extremely flexible sealants. They are based on a polyurethane prepolymer terminated by a specific and unique tri-functional alcoxy-silane end-group.

They represent so-called "hybrid systems" and combine in an ideal way the advantages of polyurethane chemistry with the chemistry of silicones.

The most important advantages of Desmoseal® S:

• Good adhesion to different substrates (without primer) combined with good cohesion and elasticity
• Bubble-free curing even in high humidity environments and at higher bulk (no formation of CO₂)
• Can be overcoated
• Highly reactive (reduced need for catalyst)
• Good adhesive strength
• Can be formulated tin-free
• Free of isocyanates
• Good elastic recovery
• Excellent mechanical properties
  • Tensile strength 2-5 MPa
  • Elongation at break 100-900%
  • Shore A 15-70
  • Modulus @100% 0,3-2,5 MPa

Bayer MaterialScience's STPs provide outstanding physical properties and they meet the requirements of the adhesives and sealants manufacturers for modern one-component formulations in the construction and industrial applications. Due to their versatility and broad property profile, other applications are possible as well, like the automotive industry, modern housing systems and sealant systems in boating. Please contact our experts to discuss your ideas.

Product examples:

	Viscosity Pas	Molecular weight	Plasticizer
Desmoseal® S XP 2458	40	medium	10% Mesamoll	„hard“, high modulus, low elasticity
Desmoseal® S XP 2636	35	high	------	„soft“, low modulus, high elasticity

Have a look at this presentation for additional details:

Presentation for the ECS 2007: "Silane Terminated Prepolymers"

More on sealants in general as an application.

Brochure: Prepolymers - Products & Applications