Epoxy modified with urea-based ORMOSIL and isocyanate-functionalized polybutadiene: Viscoelastic and adhesion properties

Abstract

Epoxy networks present good adhesion properties but are brittle in nature due to the high crosslink degree. The modification with silica particles and rubber can be a useful approach for improving adhesion properties without affecting the thermal properties and stiffness. This work present a new epoxy system modified by a combination of organically modified silica (ORMOSIL) containing phenyl ureasil groups and liquid polybutadiene terminally functionalized with isocyanate groups. The ORMOSILs were prepared by a sol-gel process involving TEOS and phenyl ureasil-silane in methanol or ethanol. The synthesis in methanol resulted in smaller particle size and a better incorporation of the functionalized silane. Both epoxy resin (ER) and the rubber-modified epoxy (ERPBNCO) presented superior adhesion properties by using ORMOSIL prepared in methanol as the solvent [ORMOSIL(M)]. The combination of ERPBNCO and ORMOSIL(M) provide adhesive with superior adhesion properties while keeping the stiffness and glass transition temperature of the matrix.