The preparation and application of CTBN modified epoxy adhesive

Purpose – The purpose of this study is to investigate the effects of two epoxy ratio and carboxyl-terminated butadiene solid rubber (CTBN) content on adhesive and flexible copper clad laminate (FCCL) performance. The epoxy adhesive used for FCCL was prepared with epoxy resin of 901 and 6128 as matrix and CTBN as toughener. Design/methodology/approach – The epoxy adhesive was prepared with epoxy resin as matrix, CTBN as toughener and 4,4′-diamino diphenyl sulfone as curing agent in solvent of butanone by mechanical agitation. The adhesives were cast on the polyimide film; subsequently, the polyimide film was dried at 160°C for 3 min to remove the solvent. Then, it was laminated with copper foil at 180°C with the pressure of 12 MPa for 3 min. The FCCL was obtained after heating for 3 h in a vacuum oven at 160°C. The structure and dielectric properties of cured adhesive, surface morphology of peeling FCCL and mechanical properties of FCCL were determined. Findings – CTBN was found to react with the epoxy resin during the curing process, with the rubber phase being precipitated and dispersed in the epoxy matrix. The relative dielectric constant and the dielectric loss tangent slightly increased with increasing CTBN content. The peeling strength of FCCL increased accompanied by a decrease of folding resistance with the increase of 901 content. Further, with the addition of XNBR, the peel strength of FCCL increased, as well as the folding resistance of FCCL, but at a higher XNBR level of 20 weight per cent, the folding resistance of FCCL tended to decrease. Research limitations/implications – In the study reported here, the effects of different epoxy resin molecular weight and CTBN content were investigated. Results of this research could benefit in-depth understanding of the influence of epoxy resin molecular weight and CTBN content on adhesive performance and could further promote the development of epoxy adhesive. Practical implications – The adhesion of epoxy adhesive prepared from epoxy resin with different molecular weight and CTBN increased, leading to the increase in peeling strength and folding resistance of FCCL. Social implications – The peeling strength of FCCL increased as the adhesion strength of epoxy adhesive increased by adding CTBN, making FCCL widely applicable. Originality/value – The mechanical properties of epoxy adhesive were increased by adding CTBN. The effects of CTBN on the microstructure and properties of FCCL were discussed in detail.