Organometallic complexation phenomenon observed during the natural aging of polyester urethane in the presence of iron corrosion

Abstract

Abstract Shoes with polyester urethane soles have been stored for 3 decades in a museum environment after several months of mining use. Upon observation of sole material ageing under natural conditions, the shoes were laboratory stored since 2017 in order to evidence and follow signs of polyester urethane degradation. This study aims at characterizing a complex degradation material found on several shoes of the museum’s collection. Combining chemical composition analysis (EDX), mass spectroscopy (EGA-MS, py-GCMS) and vibrational spectroscopy (Raman and IR), results evidence the presence of iron carboxylates in different coordination modes. This study highlights the formation of a hitherto unknown degradation material of polyester urethane: an organometallic complex with iron ions coordinated with carboxylic rests of polyester polyol chains. The compound arises from the interaction between iron ions from the corrosion of structural metallic elements of the sole, and the polyester polyol fragments from the hydrolysis of the polyester urethane.