Difunctional and Multifunctional Epoxy-Terminated Silicones

These include lower molecular weight siloxanes with discrete structures and higher molecular weight silicones with either pendant or terminal epoxy functionalization. Depending on specific structures and formulations, they selectively impart a wide range of properties associated with silicones⁠—low-stress, low temperature properties, dielectric properties, and release. Properties of cured silicone-modified epoxies vary from hydrophilic to hydrophobic depending on the epoxy content, degree of substitution, and ring-opening of epoxides to form diols. The ring-strained epoxycyclohexyl group is more reactive than the epoxypropoxy group and undergoes thermally- or chemically-induced reactions with nucleophiles including protic surfaces such as cellulosics of polyacrylate resins.

The compatibility of epoxy-functional silicones with conventional epoxies varies. In simple unfilled systems, total solubility is required. For filled systems, it is often desirable to consider systems that are miscible but have only limited solubility since microphase separation can allow a mechanism for stress-relief. Epoxysilicones with methoxy groups can be used to improve adhesion to substrates such as titanium, glass, or silicon. They also can improve chemical resistance of coatings by forming siloxane crosslinks upon exposure to moisture.