Maciej Celiński

W zakładach przetwórstwa rolnego istnieje możliwość wystąpienia atmosfery wybuchowej. Pył powstający w takich procesach, jak mielenie, przesiewanie czy transport zboża, stanowi potencjalne źródło zapłonu i wybuchu w instalacji przemysłowej. Statystyki pokazują, że roczna światowa produkcja zbóż w 2019 r. przekroczyła 2,7 mld ton. Taka ilość pylistego materiału znacznie zwiększa ryzyko wystąpienia pożaru lub wybuchu podczas produkcji, transportu i przetwarzania. Z powodu zagrożenia wybuchem zakłady zajmujące się składowaniem i przetwarzaniem zbóż muszą być wyposażone w odpowiednie zabezpieczenia. W artykule przedstawiono parametry wybuchowe pyłów zbóż najczęściej stosowanych w Polsce oraz rodzaje typowych zabezpieczeń w instalacjach przemysłowych.

In this paper, the fire behavior of unsaturated polyester resin (UP) modified with L-histidinium dihydrogen phosphate-phosphoric acid (LHP), being a novel intumescent fire retardant (IFR), was investigated. Thermal and thermomechanical properties of the UP with different amounts of LHP (from 10 to 30 wt. %) were determined by thermogravimetric analysis (TG) as well as dynamic mechanical thermal analysis (DMTA). Reaction to small flames was studied by horizontal burning (HB) test, while fire behavior and smoke emission were investigated with the cone calorimeter (CC) and smoke density chamber. Further, the analysis of volatile products was conducted (TGA/FT-IR). It was observed that the addition of LHP resulted in the formation of carbonaceous char inhibiting the thermal decomposition, burning rate and smoke emission. The most promising results were obtained for the UP containing 30 wt. % of LHP, for which the highest reduction in maximum values of heat release rate (200 kW/m²) and total smoke release (3535 m²/m²) compared to unmodified polymer (792 kW/m² and 6895 m²/m²) were recorded. However, some important disadvantage with respect to water resistance was observed.

Two phosphorus-containing cage-like silsesquioxane derivatives were synthesized as reactive or additive flame retardants for epoxy resin. The silsesquioxanes were obtained via an epoxide ring-opening reaction using a 10-hydroxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPA). In one derivative containing in its structure 4 glycidoxypropyl and 4 phosphate groups, denoted as 4P4GS, only half of the epoxy rings was reacted with phosphate to obtain a reactive additive, while in the second derivative containing 8 phosphate groups, denoted as 8PS, all epoxy groups were converted, thus an additive modifier was obtained. The silsesquioxanes containing phosphorus atoms and the reactive phosphorus-free silsesquioxane derivative (octakis[(3-glycidoxypropyl)dimethylsiloxy]octasilsesquioxane (8GS)) were used to prepare hybrid materials based on epoxy resin. To compare the impact of the structure of silsesquioxane derivatives on the properties of hybrid materials, a number of samples containing 1, 5, and 10% of the modifiers making a series of epoxy materials containing additive or reactive modifiers, were obtained. The modified epoxies were studied using scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), nanoindentation, water contact angle, and cone calorimetry tests to assess the effects of the modifier structure on the physicochemical properties of the investigated materials.

A novel flame retardant system, embraced shell (S) and histidine diphosphate (H) as intumescent flame retardant developed in the Department of Chemical, Biological and Aerosol Hazards laboratory, was added to the epoxy resin and examined. The influence of flame retardant system on the thermal stability was assessed based on thermogravimetric analysis (TGA). Moreover, the flame retardant components were characterized by grain size distribution. It was found that the incorporation of the developed flame retardant system caused the formation of thermal stable char, which may inhibit the burning process.

A novel intumescent flame retardant system based on shell (S) and histidine diphosphate (HF) was developed and introduced into the epoxy resin in order to verify its effectiveness in the inhibition of the burning process. To confirm the structure of HF, powder X-ray diffraction (XRD) was used. The influence of the flame retardant system on the burning and smoke emission of the resin was assessed based on cone calorimeter (CC) measurements. Moreover, structural evaluation of polymeric materials was carried out using scanning electron microscopy (SEM). It was found that the incorporation of the developed flame retardant system caused the formation of a protective layer in the form of char, which reduced burning process and smoke emission of the epoxy resin. The obtained results were better than those generated by commercial intumescent fire retardant.

The influence of plant fillers on the flammability and smoke emission of natural composites was investigated. Epoxy composites with 15, 25, and 35 wt % of walnut and hazelnut shell, as well as sunflower husk, were prepared and examined. The ground organic components were characterized by grain size distribution, thermogravimetric analysis (TGA) and microstructure observations (SEM). The composite materials were subjected to dynamic mechanical analysis (DMA) and structural evaluation with scanning electron microscopy. Cone calorimeter tests and TGA determined the influence of plant waste filler addition on thermal stability and flammability. Moreover, the semi-volatile and volatile compounds that evolved during the thermal decomposition of selected samples were identified using a steady state tube furnace and a gas chromatograph with a mass spectrometer. The intensity of the degradation reduced as a function of increasing filler content, while the yield of residue corresponded to the amount of lignin that is contained in the tested plants. Moreover, the incorporation of agricultural waste materials resulted in the formation of a char layer, which inhibits the burning process. The yield of char depended on the amount and type of the filler. The composites containing ground hazelnut shell formed swollen char that was shaped in multicellular layers, similar to intumescent fire retardants.