Abstract
Aqueous ethylene glycol and propylene glycol solutions are the principal antifreezes used as heat transfer fluids in flat-plate solar collector systems. Acidic degradation produces formed in the thermal oxidation of these solutions have been analyzed using ion chromatography (IC) and the ion-chromatography exclusion (ICE) method of analysis. The primary acidic degradation product found in the case of ethylene glycol solutions was glycolic acid. Propylene glycol solutions yielded mainly lactic acid. The presence of metallic copper significantly increased the amount of degradation products over that produced in the absence of metal. Solutions heated in the presnce of metallic aluminum were only slightly more degraded than those heated without metal, but contained relatively large amounts of formic acid. Only traces of formic acid were observed when the glycol solutions were heated in the absence of metal or in the presence of metallic copper.
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