Development of a two-component structural adhesive for bonding of metals and polymeric composites

To minimize the structure distortion and potential de-bonding in adhesive bonding of dissimilar materials (e.g., metals and polymeric composites), a two-component (2 K) low temperature cure modified adhesive consisting of 93.5 wt% commercial Henkel 5089 adhesive, 2.5 wt% N-(2-Hydroxyethyl) ethylenediamine (AEEA) and 4.0 wt% 2-ethyl-4-methylimidazole (2,4-EMI) was formulated. Experimental results showed that the use of the modified adhesive lowered the curing temperature from recommended 177 degrees C (for 20 min) for Henkel 5089 to 100 degrees C (for 20 min) or 120 degrees C (for 10 min) for AA6061-AA6061 joint, and 120 degrees C (for 20 min) or 130 degrees C (for 10 min) for AA6061-C-f/PA6 (Nylon 6) and C-f/PA6-C-f/PA6 joints, respectively, due to the faster curing reaction caused by the combined addition of AEEA and 2,4-EMI. It took 5, 3, and 2 days to cure the adhesive-bonded AA6061-AA6061, AA6061-C-f/PA6, and C-f/PA6-C-f/PA6 joints made with the modified adhesive and cured at ambient temperature, respectively. In addition, the modified adhesive had sound working life (5 h) at ambient temperature. The static strengths of all adhesive-bonded AA6061-AA6061, AA6061-C-f/PA6, and C-f/PA6-C-f/PA6 joints with the modified adhesive were hardly affected by thermal exposure cycle (i.e., exposure to 82 degrees C for 30 min). These results indicated that the modified adhesive possesses the promising characteristics for joining of similar and dissimilar materials.