エポキシ樹脂の吸水性と破壊じん性に関する研究

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The water sorption and fracture toughness characteristics of epoxide resins cured with aliphatic diamines and aliphatic dicarboxylic acid were investigated. The concentration of network chains, ν,in the cured resins was governed by the number of methylene linkages in the curing agents. The cured resin with high ν exhibited low diffusion coefficient, D, and high equilibrium water uptake, M∞. M∞ of the diamine cured system was 2.9 wt%〜1.5%, while that of the dicarboxylic acid cured system was 2.2 wt%〜1.0%. The dicarboxylic acid cured system was very sensitive to water and showed larger toughness loss after immersion in water than the diamine system. The dicarboxylic acid cured system was very sensitive to water and showed larger toughness loss after immersion in water than the diamine system. The fracture toughness, K_c, of the diamine cured resin with high ν increased after immersion in water for 600 hrs. The water sorption induced plastic flow at the crack tip, causing an increase in K_c. On the other hand, K_c of the dicarboxylic acid cured resin with low ν decreased remarkably after immersion in water for 600 hrs (and 2 hrs). It seems that the network chains at the crack tip are degraded by ester hydrolysis, resulting in an decrease in K_c.
1984-10-15