Susceptibility of Polyurethane Foam to Deterioration by Impurities or Contaminants in Ethylene Glycol Monomethyl Ether

摘要

Polyurethane foam used to suppress fire and explosion in the fuel tanks of certain aircraft normally possesses excellent storage stability in ethylene glycol monomethyl ether (EGME) and water mixtures such as would be found in fuel tank water bottoms. However, certain lots of EGME were found to cause severe degradation of foam after one week of storage at 160F in 25% EGME-75% water. A major supplier of EGME traced the cause of foam degradation to the presence of lead and/or tin at the ppm level in EGME, a condition resulting from the storage of EGME in one-gallon cans with soldered seams. Data are presented which confirm the lead ion as the cause of foam degradation and which demonstrate that certain other metal ions at the ppm level did not produce the degradation effect under the solution conditions tested. It is recommended that foam stability be studied employing typical water bottoms obtained from the field. A mechanism for metal ion-catalyzed foam degradation via hydrolysis is suggested. (Author)