Wacker to showcase silane-terminated polymers for sealants and adhesives

Munich, Germany – WACKER is all set to showcase a new generation of silane-terminated polyethers at the European Coatings Show 2025: GENIOSIL® STP-E 140 and GENIOSIL® STP-E 340. These novel polymers can be formulated into tin-free sealants and adhesives that are highly elastic and achieve a low modulus of elasticity – properties that are most desirable in the construction sector and a first in the adhesives and sealants world. Tin-free assembly adhesives are yet another area of application that can benefit from these products. With these polymers, property profiles are now possible that comparable binders fail to provide. The European Coatings Show will be held in Nuremberg, Germany, from March 25 to 27, 2025.

Laboratory tests show that sealants based on the GENIOSIL® STP-E 340 binder exhibit very good elastic recovery properties. WACKER will be premiering the product at the European Coatings Show in March. (Photo: WACKER)
The silane-crosslinking binders GENIOSIL® STP-E 140 and GENIOSIL® STP-E 340 are based on WACKER’s state-of-the-art Alpha³ technology. The polymers in question consist of both alpha and gamma-silyl groups. The alpha-silyl groups lead to greater reactivity, while the slower-reacting gamma ends have a positive impact on elastic recovery. This innovative technology thus combines the advantages of both alpha and gamma-silane-crosslinking polyethers.

Just like a conventional alpha-silane-terminated polymer, the combination of the two silane-terminated polyethers does not require a tin catalyst for curing. During crosslinking, the highly reactive alpha end literally pulls in the gamma end into the swifter curing process, which generally displays slower reactivity. After crosslinking, GENIOSIL® STP-E 140 and GENIOSIL® STP-E 340 are highly elastic. Application tests show that the silane-terminated polyethers adhere to a wide range of varying substrates.

Both binders can be processed into creep-resistant, fast-curing adhesives. They also facilitate the production of low-modulus sealants. These are flexible and, even without the application of much force, retain elasticity. Moreover, they also exhibit good elastic recovery, i.e. they return to their original length after exposure to prolonged elongation – a combination of properties that is unusual for conventional alpha-silanes.

WACKER will be showcasing its new silane-terminated binders GENIOSIL® STP E 140 and GENIOSIL® STP-E 340 at ECS 2025. Both products can be used, for example, to formulate tin-free assembly adhesives. (Photo: WACKER)
The two binders differ in terms of viscosity. At 10,000 millipascal seconds, GENIOSIL® STP-E 140 is more fluid-like than GENIOSIL® STP-E 340, which has a viscosity of 30,000 millipascal seconds. This makes it easier to tailor the finished product to meet the requirements of the relevant application.

Adhesive and sealant formulators can process GENIOSIL® STP E 140 and GENIOSIL® STP-E 340 in a similar fashion as conventional silane-terminated polyethers. Even formulations without solvents and plasticizers are possible. Incompatibilities with ester-based additives are eliminated, as the polymers crosslink without a tin catalyst. This increases the scope for novel formulation develop-ments and improves the storage stability of the formulated finished product.

Both binders can be blended with all GENIOSIL® silane-terminated polyethers. It is thus possible to tailor the crosslinking rate, skin-over time, and the mechanical and elastic properties of the finished products to precisely meet the requirements of the end user. The new silane-terminated polyethers therefore can now address a diverse range of tin-free formulated adhesives and sealants.

Adhesives and sealants based on GENIOSIL® STP-E 140 and GENIOSIL® STP-E 340 can be processed and applied without any need to change existing mixing or processing methods. Particularly the craftsman will benefit from the characteristic ease in handling such hybrid products.

Visit WACKER at the European Coatings Show 2025 from March 25 to 27 in Hall 1, Booth 1-206