Preparation And Characterization Of Flame Retardant Polystyrene Composite Materials

Polystyrene is a colorless and transparent thermoplastic which synthesized by free radical reaction of styrene monomer. Due to its great water resistance and light transmission, chemical corrosion resistance excellent processing performance and easy coloring, low price and so on, PS is widely used in our lives.However, Polystyrene composed of only two elements (carbon and hydrogen) which resulted in highly flammable PS resin and and multiple hazardous gas emissions. Moreover, the droplet phenomenon of the PS resin could cause secondary disasters. All the above reasons are greatly limiting PS resin widespread used in different fields. So, if we want to develop applications of polystyrene resin, the polystyrene resin modified with fire-retardant need be carried out.Halogen flame retardant and inorganic flame retardants have accounted for more than80%in flame retardant modification of polymer. While traditional halogen flame retardants can generate carcinogenic substances, such as "Dioxins", which threatens to human beings and the environment. So, as early as2006, European Union have implemented RoHS bans, to restrict or prohibit the flame retardants applications which can produce carcinogens. Inorganic materials as flame retardants must be added to reach a high level in compound system, and the poor compatibilities between inorganic flame retardants-polymers, and inorganic fillers shows a negative impact on mechanical properties of the polymers. So,in this study, in order to obtain a low-cost fire retardant polystyrene composites with excellent mechanical properties, we chose the intumescent flame retardant to modify polystyrene resin.Ammonium polyphosphate is more representative in intumescent flame retardant, it can release ammonia and water vapor, forming a water-based substances such as phosphate after combustion heat, In the process of flame retardant, it just released ammonia and water vapor, toxicity is greatly less than other kinds of flame retardants.Expanded graphite is a kind of carbon material through special processing, its own volume will increased to hundred times after heat. With high inflation rate, low heat and no pollution, so it has excellent flame retardant properties. This topic used ammonium polyphosphate and expanded graphite to modify the flame retardant of polystyrene resin, and calcium carbonate was added to the flame retardant system for solved the problems which encountered in the process of the experimental.The flame retardant performance of the compounds were compared by the limited oxygen index and UL-94vertical burning tests. The surface micro topography and chemical structure of the carbon layer were characterized with X- ray diffraction (XRD), scanning electron microscope (SEM), fourier transform infrared spectroscopy (FTIR). Moreover, the mechanism of the APP/EG/CaCO3/PS composite flame retardant carbon layer formation was discussed.The results showed that:in APP/EG system, when APP/EG=3:1, the limiting oxygen index of the composite materials (LOI) reached27.2%, UL-94tested at v-1, the carbon residue rate increased to17.48%and a small amount of smoke produced. When the percentage change is1:1, the LOI reached28%, UL-94tested at v-0, the carbon residue rate increased to19.68%, the phenomenon of molten drops disappeared and no smoke produced. But for "popcorn effect "of EG, the intensity of carbon layer structure formed is lower during the combustion, which weaken the flame retardant effect. After added the calcium carbonate in the APP/EG system (APP/EG/CaCO3=20/10/10), the PS resin fire-retardant effect greatly improved, the LOI rised31.2%,no phenomenon of molten drips happened, UL-94tested at v-0, no smoke produced, and carbon residue reached28.85%. In addition, the carbon layer is denser and the structural strength increased which could provide a better function of protection and isolation. According to the analysis, the APP/EG and APP/EG/CaCO3flame retardant systems is mainly based on condensed phase mechanism, and supplemented by vapor phase. Meanwhile, the use of calcium carbonate (CaCO3) effectively adjusts the APP decomposition temperature and increases the structural strength of carbon layer, as well as inhibits EG’s "popcorn effect ".