An experimental and numerical model for the release of acetone from decomposing EVA containing aluminium, magnesium or calcium hydroxide fire retardants

Abstract

Recent studies have identified acetone as an unexpected pyrolysis product of EVA containing aluminium or magnesium hydroxide fire retardants. It is thought that the freshly formed, open-pored, metal oxide, a thermal decomposition product of the metal hydroxide, traps acetic acid released from EVA and catalyses its conversion to acetone. Such a ketonisation reaction is well-established but the intermediate steps that result in acetic acid conversion to acetone in the presence of a metal oxide, trapped within the polymer matrix, have not been reported. This study used three model metal acetates: aluminium acetate, magnesium acetate and calcium acetate, to chemically represent the proposed metal acetate intermediate complexes. This provides crucial information on the kinetics of acetic acid trapping and subsequent acetone release during decomposition studied by TGA-FTIR, which has been used to generate kinetic models within a pyrolysis programme (ThermaKin), in order to quantitatively understand the processes occurring in fire retardant EVA. The benefit of using metal acetates is that they are simple enough to allow isolation of the chemical process of interest from the complications of acetic acid release from EVA and transport through the polymer matrix