New Silane Binders for High Elastic, Tin-Free Sealants & Adhesives
A new range of new silane-crosslinking binders are being utilized to create highly elastic tin-free sealants and adhesives as well as low-modulus, fast-curing adhesives. The adhesive & sealant manufacturer, Wacker, reports that new laboratory reports show that sealants based on their GENIOSIL® STP-E 340 binder exhibit very good elastic recovery properties. Based on WACKER’s Alpha³ technology, these novel polymers can be formulated into tin-free sealants and adhesives that are highly elastic and achieve a low modulus of elasticity. Such properties are desirable in the construction sector and, reportedly, 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 company reports.
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.
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 developments and improves the storage stability of the formulated finished product.
Source: Wacker