Synthesis of borosiloxane oligomers containing vinyl and epoxy groups for improving adhesion of addition-curable silicone rubber with epoxy resin

In this research, a kind of borosiloxane oligomer (BSiO^Vi) containing vinyl and epoxy groups, was synthesized as surface treatment agent to improve the interfacial adhesion property between addition-curable liquid silicone rubber (AL-SR) and epoxy resin (EP). The chemical structure of the BSiO^Vi was studied by Fourier Transform Infrared Spectra (FT-IR), Gel Permeation Chromatography (GPC), Nuclear Magnetic Resonance Spectroscopy (¹H-, ¹³C-, ²⁹Si-and ¹¹B-NMR) and Thermo Gravimetric Analysis (TGA). The adhesion strength between EP and AL-SR was tested using Morphological analysis and Tensile Lap Shear test. The test results showed that the BSiO^Vi with vinyl and epoxy groups could significantly improve the strength of adhesion between EP and AL-SR The highest adhesion strength value (3.2 MPa) was collected from silicone rubber breakage for BSiO^Vi/EP/AL-SR system. Furthermore, the adhesive mechanism between EP and AL-SR was analyzed. The improvement of adhesion strength was a result of chemical bonding, because the vinyl and epoxy groups of BSiO^Vi could react with the active hydrogen of AL-SR and amino groups of EP surface respectively. In conclusion, the BSiO^Vi can solve the interfacial adhesion problems effectively and the feature of BSiO^Vi have great application potential to solve the adhesion problem for AL-SR with other materials possessing amino groups.