Abstract
Aromatic-amine hardeners impart high deformation temperature, excellent chemical and electrical properties to cured epoxy resins. One of the disadvantages, however, is that some are solid at ordinary temperature and must be heated to melt before use. We have prepared liquid hardeners which gave to cured, epoxy excellent properties comparable to those of the aromatic-amine cured epoxy.
Fluidised forms of m-phenylenediamine were prepared by reacting at least 3 parts (by mole) of phenyl-, allyl-or butyl-glycidyl ether with 10 parts of m-phenylendiamine at 100-120°C for 6 hr. The fluids with these compositions are essentially stable solutions of m-phenylenediamine in the adducts of m-phenylenediamine and the ethers. The storage stability of these fluids was excellent even at a temperature lower than 10°C.
Viscosity of the adduct mixture had a minimum value at the (m-phenylenediamine/ether) mole ratio of 100/33; the adduct mixtures with this mole ratio were thus employed as hardeners for an epoxy resin (bisphenol A-epichlorohydrin condensation type) with molecular weight of about 380. The resultant coatings possessed the electric, thermal as well as chemical resistances which were comparable to those obtainable from m-phenylenediamine and better than those obtainable from Epikure Z.
The weights per one mole of available hydrogen atom of the adducts of m-phenylenediamine with phenyl-, allyl-and butyl-glycidyl ethers are 47, 43 and 44, respectively. These adducts in combination with triethylenetetramine or tetraethylenepentamine can be applied to the drip process as suiltable hardeners.
The adducts prepared by reacting less than 3 parts (by mole) of the ethers with 10 parts of m-phenylenediamine were solid. The effects of the glycidyl ethers on various properties of the cured epoxy resins and the adduct eutectic mixtures are compared with those in the casting systems where the glycidyl ethers are used as diluent.
