Prepolymer Endcapper

Silane-terminated polyurethanes can be prepared by reacting traditional NCO-terminated urethane prepolymers with secondary aminosilanes. Both aminosilanes react very fast with free isocyanate groups and lead to a high converted silane-endcapped product. Side reactions can be significantly reduced.

Besides, silane endcappers help formulators to comply with REACH regulation by neutralizing any free NCO groups.

There are many silanes in market which are most recommended for endcapping Polyurethanes. It leads to colourless low-viscosity PU prepolymers with improved UV stability and reduced yellowing tendency of sealants. Another benefit of silane is that it does not contain traces of toxic aniline.

Examples of applications where these silanes are used includes polyurethanes for structural adhesives, parquet adhesives and over-paintable hybrid sealant.

The resulting adhesive/sealant will exhibit higher adhesion performance and mechanical properties. Benefits gained from endcapping polyurethane prepolymers are:

Higher adhesion and mechanical performances
Improved durability
Higher throughput due to very fast reaction with NCO groups
No unreacted residual isocyanate helping compliance with REACH regulation.