Poly(acrylate/siloxane) hybrid adhesives for polymers with low surface energy

Formulation, polymerization and performance of a new class of adhesives for bonding to low surface energy plastic substrates are described. The adhesives result from the independent polymerization of silicone oligomers and acrylic monomers. The polymerization of the acrylic phase and adhesion promotion to plastics is catalyzed by decomplexation and oxidation of trialkylborane–amine or -aminosilane complexes. The polymerization of the silicone phase is catalyzed with tin or titanium catalysts for silanol condensation reactions or platinum catalysts for hydrosilylation. A one-part adhesive system is also described in which ambient moisture reacts with vinyltriacetoxysilane to produce silanol and acetic acid. The acetic acid then protonates the amine of the catalyst complex freeing trialkylborane, which initiates acrylic polymerization. The incompatibility of acrylic and siloxane phases is mitigated by the use of acrylate functional siloxane monomers to lower interfacial tension. Additional phase compatibility is obtained by having the acrylate and siloxane reactive components polymerize at approximately the same rate upon mixing. Using this strategy, the hybrid adhesives achieve very good adhesion to many difficult-to-bond plastic substrates at temperatures ranging from −40 to 150 °C.