Preparation And Properties Of Flexible Epoxy-based Electrically Conductive Ink

The application of epoxy resins to flexible conductive ink has been limited due to disadvantages of epoxy resins, including low ductility and brittleness. In this paper, two different methods including taking Polyetheramine(D-400, D-2000) as flexible curing agent and using a carboxylate-containing terpolymer(MC42) to toughen epoxy resins E51, were applied to improve the flexibility of epoxy-based conductive ink.D-400 was applied as flexible curing agent to prepare epoxy/ polyetheramine based conductive ink. The effects of cure condition and content of Cu@Ag powder on volume resistivity of the ink were investigated. The results indicated that the optimal conditions of preparation and curing of the ink were including 70wt% of Cu@Ag powder, 56 phr of D-400, 115℃ of curing temperature and 3.0h of curing time, at which the volume resistivity reached up to 1.57 × 10-3Ω ? (equivalent to 6.37 × 104 S ? of conductivity).The compound of D-2000 and D-400 was utilized as flexible curing agent to further improve the flexibility of the ink. The effects of mass ratio of D-2000/D-400 on the volume resistivity, flexibility, and adhesion of the ink were investigated. The results showed that while increasing the mass ratio of D-2000/D-400 from 0 to 0.6, the flexibility of the ink improved significantily, all adhesion grades of conductive layers to PET substrate maintained at level zero. The compound of D-2000/ D-400 made the crosslinking destiny and volumetic shrinkage of epoxy resins decrease 76.20% and 60.60%, respectively, which resulted in the volume resistivity of conductive ink increasing 40.60%.MC42/ E51-3055 based conductive ink was prepared by applying MC42 to toughen E51 and taking amino-containing silicon resin(DOW 3055) as curing agent. The effects of content of Cu@Ag powder, cure condition and the content of MC42 on volume resistivity of the ink and the effects of the content of MC42 on the flexibility, adhesion, thermal stability and aging resistant property of the ink were also investigated. It’s found that the best condition of preparing and curing the ink was that the content of Cu@Ag powder, mass ratio of MC42/E51-3055, mass ratio of 3055/E51, curing temperature and curing time were 70wt%, 4: 6, 1.5: 1, 100℃, and 2.0h, respectively. And the volume resistivity reached up to 8.69 × 10-4Ω ? (equivalent to 1.15 × 105 S ? of conductivity) under the best preparation and curing condition.The addition of MC42 could not only significantly decrease the volume resistivity of the ink, but also improved its flexibility. Increasing the content of MC42 in the binder from 0 to 50%, the volume resistivity decreased 65.8%, the flexibility of the ink improved evidently, the adhesion grade of the ink to PET substrate droped from level zero to level one, the initial thermal decomposition temperature of the ink decreased from 250℃ to 200℃; after aging 500 hours at 85℃/85%RH, the resistance shift o f the ink increased from 7.5% to 17.0%.