Following a waste-to-wealth approach, humic acid (HA) was exploited as a flame retardant additive. The effect of its addition alone and in combination with urea (UR) and ammonium polyphosphate (APP) on the thermal, fire, and mechanical performances of a bisphenol A diglycidyl ether (DGEBA)-based epoxy resin modified with (3-aminopropyl)-triethoxysilane (AP) and cured with aliphatic isophoronediamine (IDA) has been investigated. Unlike in previous studies, a UL 94-V-0 classification was achieved for epoxy resin containing HA at 6 wt % and APP at only 1 wt % phosphorus (P) loading. The presence of silicon-modified epoxy chains ameliorated the distribution of the biowaste within the resin, and the addition of HA alone avoided melt dripping. Besides, APP and UR promoted a remarkable reduction (up to 52%) of the peak heat release rate (pHRR) values and a significant delay (up to 21%) of the time to ignition in cone calorimetry tests, and hence an increase (up to 1.8 min) of the time to flashover, without any detrimental effect on the overall mechanical behavior. The evolved gas, thermal, and fire analysis was used to propose the combined mode of action of HA, UR, APP, and silicon in the fire performance improvement of the hybrid epoxy system.

In this work, three biochars, deriving from soft wood, oil seed rape, and rice husk and differing as far as the ash content is considered (2.3, 23.4, and 47.8 wt.%, respectively), were compounded in an ethylene vinyl acetate copolymer (vinyl acetate content: 19 wt.%), using a co-rotating twin-screw extruder; three loadings for each biochar were selected, namely 15, 20, and 40 wt.%. The thermal and mechanical properties were thoroughly investigated, as well as the flame retardance of the resulting compounds. In particular, biochar, irrespective of the type, slowed down the crystallization of the copolymer: this effect increased with increasing the filler loading. Besides, despite a very limited effect in flammability tests, the incorporation of biochar at increasing loadings turned out to enhance the forced-combustion behavior of the compounds, as revealed by the remarkable decrease of peak of heat release rate and of total heat release, notwithstanding a significant increase of the residues at the end of the tests. Finally, increasing the biochar loadings promoted an increase of the stiffness of the resulting compounds, as well as a decrease of their ductility with respect to unfilled ethylene vinyl acetate (EVA), without impacting too much on the overall mechanical behavior of the copolymer. The obtained results seem to indicate that biochar may represent a possible low environmental impact alternative to the already used flame retardants for EVA, providing a good compromise between enhanced fire resistance and acceptable mechanical properties.

In this work, fire-retardant systems consisting of graphene nanoplatelets (GNPs) and dispersant agents were designed and applied on polyethylene terephthalate (PET) foam. Manual deposition from three different liquid solutions was performed in order to create a protective coating on the specimen’s surface. A very low amount of coating, between 1.5 and 3.5 wt%, was chosen for the preparation of coated samples. Flammability, flame penetration, and combustion tests demonstrated the improvement provided to the foam via coating. In particular, specimens with PSS/GNPs coating, compared to neat foam, were able to interrupt the flame during horizontal and vertical flammability tests and led to longer endurance times during the flame penetration test. Furthermore, during cone calorimetry tests, the time to ignition (TTI) increased and the peak of heat release rate (pHRR) was drastically reduced by up to 60% compared to that of the uncoated PET foam. Finally, ageing for 48 and 115 h at 160 °C was performed on coated specimens to evaluate the effect on flammability and combustion behavior. Scanning electron microscopy (SEM) images proved the morphological effect of the heat treatment on the surface, showing that the coating was uniformly distributed. In this case, fire-retardant properties were enhanced, even if fewer GNPs were used.