Fast and environmentally friendly reaction 

Silanes with double bonds are used as co-monomers to incorporate them into the polymer chain via free-radical polymerization. As a result, the organofunctional silane becomes part of the polymer backbone. A typical example is the use of Dynasylan® MEMO as a monomer in an acrylate matrix. 

Moreover, the Dynasylan® portfolio also contains several silanes that can be reacted with functional groups in the polymer. For this, silanes are incorporated into the polymer matrix so that they react with the functional groups in the polymer and form a covalent bond. This improves adhesion to different substrates such as metal, glass or ceramics, and the chemical and mechanical properties of the adhesive can be optimized. 

An important application is the production of moisture-curing silane-modified polymers. In this case, the silane function reacts terminally with functional groups on the polymer. The resulting silane-modified polymer adhesives and sealants (SMPs) cure under the influence of atmospheric moisture with hydrolysis and condensation. 

Specialty secondary amino silanes from the Dynasylan® product group can be reacted with isocyanate prepolymers. The aim here is to produce environmentally friendly, moisture-crosslinking polymers (STPU, silane-terminated polyurethanes) that serve as crosslinking polymers for adhesives and sealants. The incomplete conversion can be used to impart silane functionality to the polymer. In this way, the adhesion promoter can be placed on the polymer to avoid possible migration. This is especially important for adhesives and sealants that come into contact with foodstuffs in order to meet particularly stringent specifications in this area. 

By reacting silanes with the polymers within their own companies, customers can formulate tailor-made SMPs to meet market demands while also ensuring fast and environmentally friendly curing and crosslinking processes in what is a rapidly growing class of adhesives and sealants. 

A further specialty application is the use of silanes as sustainable endcappers for functionalizing polymers. For many years, polyurethane-based adhesives and sealants have been available in which curing and crosslinking occur as a result of the isocyanate end groups (NCO groups) reacting with moisture. However, these isocyanates are deemed harmful to health as they irritate the skin and respiratory tract. 

Due to this physiological effect, many manufacturers of adhesives and sealants wish to replace these isocyanate prepolymers with alternatives that are not a health hazard but which still react with moisture. Correspondingly, Evonik offers a range of specialty silanes for modifying adhesives and sealants. 

Dynasylan®, for example, enables the fast application of NCO-containing prepolymers with highly reactive secondary amino silanes – with no undesirable effects. These new binding systems are then used, for example, in structural adhesives, parquet glue or hybrid sealants and can be recoated. Evonik’s portfolio features numerous silanes for manufacturers to choose from.

When used as an adhesion promoter in adhesives and sealants, Dynasylan® 1189 primarily serves to functionalize polymers with amino-reactive groups, such as isocyanate prepolymers. The extremely fast reaction of the silane with the free isocyanate groups creates binding agents with outstanding moisture-curing properties that are also environmentally friendly. These can then be processed to create innovative adhesives and sealants. Moreover, Dynasylan® 1189 ensures sufficiently quick curing and a high crosslinking density in the end product. 

Due to its structure, Dynasylan® 1124 can be used as an adhesion promoter and for the subsequent modification of suitable prepolymers. Thanks to its outstanding adhesion properties on metals and glass, however, its main strength is its function as an adhesion promoter in polyurethane – either when used directly as an additive, or as a highly efficient primer component. Dynasylan® 1124 also works as an endcapper. 

• Improves adhesion properties 
• Fast reaction with the polymer 
• Thermal stability 
• Enhanced mechanical properties 
• Avoiding of migration