The influence of metal hydroxide fire retardants and nanoclay on the thermal decomposition of EVA

Ethylene-vinyl acetate (EVA) copolymers compounded with mineral filler fire retardants, such as aluminium hydroxide (ATH) and magnesium hydroxide (MH) represent an important class of fire-safe materials, especially as PVC replacements in the cable industry. The thermal decomposition of these materials has been investigated in the presence or absence of montmorillonite nanoclay using simultaneous thermal analysis (STA) interfaced to a Fourier transform infrared spectrometer (FTIR) for analysis of volatiles. STA-FTIR spectra were deconvoluted to give profiles of individual species' evolution as a function of temperature, in order to identify the individual processes involved. The first step of the degradation, the loss of acetic acid by chain stripping, has been shown to be accelerated by the presence of clay but changed to a loss of acetone by mineral filler fire retardants. This is ascribed to the catalytic properties of the freshly formed alumina and magnesia surfaces. The products of the second step of decomposition are also changed by the various additives.