Mechanism of adhesion of low surface energy materials treated with trialkylborane

Excellent adhesion to low surface energy materials without surface pretreatment was obtained by acrylates polymerization initiated by trialkylborane at room temperature. The adhesion mechanism was elucidated by electron spin resonance (ESR) and gas chromatography–mass spectroscopy (GC–MS) analysis based on model compound and chain transferring agent technologies. On the other hand, polypropylene (as one kind of low energy surface materials) was treated with trialkylborane and its effects were also studied by attenuated total reflection Fourier transform infrared spectroscopy (FTIR-ATR) and Raman spectroscopy, static contact angle measurements. The result provided further supports the elucidated mechanism.The results showed the adhesion resulted from the monomer’s graft on the surface of low surface energy materials. The graft resulted from the hydrogen abstraction reaction of materials (not less than three hydrogen sites) by alkoxyl and other radicals. These radicals came from oxidation of trialkylborane through the cleavage of O−O bond of R2BOOR. The adhesion was caused neither by the materials’ surface energy improvement nor by the copolymerization of polymerizable monomers and unsaturated groups on the surface of materials.