Synthesis of metal-containing epoxy polymers

Abstract

Cobalt, nickel, copper and zinc tetradentate Schiff's base complexes have been synthesized and used as crosslinking agents for the synthesis of metal containing epoxy polymers. The metal complexes have been synthesized by adding aqueous solutions of metal acetates or metal sulfates into methanolic solutions of 2,4-dihydroxybenzaldehyde and 1,3-diaminopropane. The metal complexes made from metal acetates are more stable and can be obtained in higher yields than complexes made from metal sulfates. The metal complexes were identified by elemental analysis and IR spectroscopy. Metal containing epoxy polymers have been synthesized by crosslinking of diglycidyl ether of bisphenol A (DGEBA) with the aforementioned metal complexes. The properties of metal containing epoxy polymers were investigated by dynamic mechanical analysis (DMA), differential scaning calorimetry (DSC) and thermogravimetry analysis (TGA). Cu-containing epoxy polymer has glass transition temperature (Tg) values up to 162ฺC and the temperature at the 30% weight loss up to 432ฺC. Ni-containing epoxy polymer has the highest thermal stability accounting from the weightloss of less than 3% upon heating at 245ฺC for 48 hours. The reactivity of the metal complexes was compared with 2,7-dihydroxynaphthalene and bisphenol A. The crosslinking reactions between DGEBA and 2,7-dihydroxynaphthalene and bisphenol A were slower than the crosslinking reactions between DGEBA and the metal complexes. The thermal properties of epoxy polymers using 2,7-dihydroxynaphthalene and bisphenol A are also poorer than those of metal containing epoxy polymers.