Thermal and flame retardant properties of ethylene vinyl acetate copolymers containing deoxyribose nucleic acid or ammonium polyphosphate

The present study was aimed to compare the effect of the presence of deoxyribose nucleic acid (DNA) or ammonium polyphosphate (APP) in ethylene vinyl acetate (EVA) copolymers, as far as their thermal and flame retardant properties are considered. Indeed, although DNA has been recently discovered as a novel green flame retardant, its performances have not been compared with a conventional flame retardant such as APP yet. With this purpose, EVA compounds containing 10 or 20 mass% of DNA or APP have been melt-blended and their thermal and flame retardant properties thoroughly investigated. The morphology of the samples has proven to be significantly different, as assessed by scanning electron microscopy: indeed, APP gave rise to numerous micro-aggregates homogeneously distributed within the polymer matrix; on reverse, DNA was finely dispersed. Both the additives have favoured the char formation, inhibiting the production of volatile species, as assessed by thermogravimetry and pyrolysis-combustion flow calorimetry. The char features of both the additives turned out to be extremely advantageous for strongly modifying the combustion behaviour of EVA, as clearly demonstrated by cone calorimetry tests.