The Evaluation of Alkyl Borane Compounds and Imidazole Borate Complexes as Initiators for Acrylic Adhesives Bonding Low Energy Substrates

Novel amido-borate initiators based on imidazolide bridged borate complexes were developed for acrylic adhesives used to bond low surface energy substrates. The focus of this development was examining the shelf life of the acrylic adhesive system as a function of the molecular architecture of the organoboron curative. The two key molecular features which significantly affect stability are: 1) the chain length of the alkyl groups on the boron atom and 2) arrangement of the imidazolide bridged borate structure. The results show that superior shelf life stability can be attained over the conventional trialkyl borane- and tetraalkyl borate-type initiators when this new family of catalysts (imidazolide borate compounds) is incorporated into the adhesive formulation without any harmful effect on cure speed.