... PROPYLTRIMETHOXYSILANE(CAS No.3068-78-8), Silane coupling agent KH-557, is a bifunctional secondary amino-functional silane. ... silane-endcapped product. Side reactions can be significantly reduced. KH-557 is the most recommended silane for endcapping Polyurethanes. ... contain traces of toxic aniline. Examples of applications where KH-557 used include polyurethanes for structural adhesives, parquet ...