Fire behaviour of biopolymer wet in flammable solvent

Several industrial processes deal with solid-liquid hybrid mixtures composed of flammable or combustible species, posing concerns about their behaviour once exposed to undesired conditions, including fires. However, a poor understanding of the safety aspects and possible synergistic effects of the species constituting the mixtures has been gained. This is particularly relevant for polymer production, where innovative materials are continuously introduced. For these reasons, this work presents an innovative and comprehensive methodology for the evaluation of microscopic and macroscopic aspects ruling the fire-behaviour of solid-liquid mixtures of carbon-based substances. Lab-scale thermal analysis (Differential Scanning Calorimetry, DSC, Thermogravimetric Analysis TGA, and TGA coupled with Mass Spectroscopy, TG-MS) and bench-scale thermal oxidative analysis (cone calorimetry) were carried out. Isothermal tests, coupled with mass spectroscopy analyses, have elucidated the chain of events occurring under pyrolysis conditions, whereas fire tests have shed light on the ignitability and the overall kinetics and exothermicity. The proposed approach was applied to the cases of Polyhydroxybutyrate (PHB), Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and PHBV-toluene mixtures. The vapour production from liquefied polymer was identified as the rate-determining and crotonic acid was identified as the species ruling the gas-phase reactivity of the polymer. Although two distinguishable behaviours were observed during the degradation of wet polymers, each of them attributable to a pure compound, toluene-polymers interactions were identified, allowing for the realisation of advanced models suitable for an optimised design of industrial processes involving wet polymers.