| Polystyrene(PS) is one of the most used plastics in our life, which obtained by polymerization of monomer styrene(SM). It is a thermoplastic that has lots of advantages, such as colorless, lower relatively density, great processing capability, good corrosion resistance, strong coloring ability and excellent electrical properties. So it has been wildly used in building, packaging and electrical fields. However, every coin has two sides. We can’t ignore the highly flammable of pure PS, it will not only produce large amount of smoke but also generate the phenomenon of melting drip. These could cause fire that damaging the environment even further harm that both in physical and in mental to people.Hence, what we have to do is to search for a suitable flame retardant to improve the flame retardancy of PS, and it is an inevitable trend to study flame retardant with high efficiency, low smoke and low toxicity, halogen-free and environment-friendly.Expandable graphite(EG) is a natural scale layered compound withconcentrated sulfuric acid, it has been proved to present heat resistant, good acid and alkali corrosion, excellent anti-bending capacity and outstanding flame retardancy. The volume expands rapidly to tens or even hundreds of times when it closes to the heat source. It is always used to be a environment-friendly flame retardant because it contains no halogen and generates non corrosive or toxic gases when burning. Ammonium polyphosphate(APP) is wildly used due to the P and N elements in it. And it has smaller relative density, higher chemical stability, lower toxicity and better dispersion than other additives. It will release NH3 and H2 O which play an important role in gas-phase and generate polyphosphoric acid which take effect in condensation-phase.In this paper, we use PS as the matrix, EG/APP as the synergistic agents and add suitable additives. By applying the method of blend modification to synthesis a kind of flame retardant material that is easy molding,environment-friendly and high-efficiency. We have optimized the formulation of materials, explored the process condition and its effect on many performance of PS composites. The flammability of composites were detected by limited oxygen index(LOI) and UL-94 test; the mechanical property of composites were investigated by electronic universal testing machine and izod impact test machine; the carbon residue and surface morphology of product were characterized by thermogravimetric(TG) and scanning electron microscope(SEM) respectively.The results showed that: The LOI value and thermal stability wereimproved significantly with the addition of flame retardant; The synergistic effect was obvious when the additive contents of flame retardant was 30 percent and the mass ratio of EG and APP was 3:1. At this scale, the LOI value could achieve 31.8% and reach V-0 in UL-94 test, and there is no melting drip;Although the addition of flame retardant reduced the mechanical property, it reached the best effect in this proportion; The carbon yield was 23.53% at 800℃;Because of the physical synergy between EG and APP, the compact carbon layer was formed, thus indicates PS composites can achieve good flame retardant effect and its main mechanism is condensed phase flame retardant; The flame retardancy of PS composites would further improving with the use of additives which reflected by the follows: the LOI value was increased(For example, the LOI value was increased from 31.8% to 33.2% with the addition of 5% PA-6),the carbon yield was further improved at 800℃(For example, the carbon yield was increased from 23.53% to 33.05% with the addition of 5% PA-6) and the density of the carbon layer was elevated to some certain extent. |
PDF Full Text Request