Study On Self-extinguishing Hips-based Composites

High impact polystyrene (HIPS) is one of the most important general plastics andis widely used due to its excellent electrical insulation, processability, good corrosiveresistance, and impact property. However, the most obvious disadvantage of HIPS isits high flammability and opious smoke-emitting property upon combustion, posing aserious hidden danger in practical applications. Thus, it is imperative to endow themwith fire retardant and smoke suppressing properties.In this paper, a series of flame retardant HIPS based composites were preparedand various means were employed to investigate the fire performance and flameretardant mechanism of the as-prepared materials. The main contents of the paper areas follows:1. Based on HIPS/bromopolystyrene (BPS) blend, antimony oxide (AO), zincborate (ZB) and organic montmorillonite (OMMT) flame retardants, a series of HIPS-based composites, such as HIPS/BPS/OMMT, HIPS/BPS/AO, HIPS/BPS/ZB,HIPS/BPS/AO/ZB and HIPS/BPS/ZB/OMMT, were prepared by melt-compounding.Oxygen index (OI), horizontal and vertical burning tests, cone calorimetry and hightemperature pyrolysis were adopted to investigate the flame retardancy and flameretardant mechanism of the composites. It has been shown that BPS itself has someflame retardant effect on HIPS, but its fire retardant efficiency is quite low. Addingmore than20phr BPS can make the blend self-extinguish in air and reach the FH-1rating in the horizontal burning test. However, using BPS alone cannot make the blendmeet the demands of any rating in the vertical burning test. Both AO and ZB displaymarked synergistic flame retardant effect with BPS. Introducing both AO and ZB canfurther improve the oxygen index value of the blend, but excessive ZB can deterioratethe vertical burning property. Under identical conditions, the synergistic efficiencybetween AO and BPS is much higher than that between ZB and BPS. The flameretardant mechanism of HIPS/BPS blend is gas phase flame retardation. After theintroduction of AO and ZB, the flame retardant mechanism of the composites is still predominantly gas phase flame retardation. With the increase of ZB loading,condensed phase flame retardation starts to play a role gradually. The introduction ofOMMT can increase the fire retardancy of HIPS/BPS blend remarkably in that thevertical burning property can met the demand of FV-0rating. The flame retardantmechanism of HIPS/BPS/OMMT has changed from the original gas phase flameretardation to synergistic flame retardation in both gas phase and condensed phase.Composites with excellent flame retardancy can also be obtained by adding ZB andOMMT into HIPS/BPS blend.2. Based on HIPS/poly(phenylene oxide)(PPO) blend and flame retardantmicroencapsulated red phosphorus (MRP), HIPS/PPO/MRP composites wereobtained by melting compound and the fire performance and flame retardantmechanism were investigated. It has been shown that there is remarkable synergisticflame retardant effect between PPO and MRP. The combination of both of them candecrease the loading of the flame retardants noticeably and flame retardantcomposites with excellent comprehensive performances can be obtained.3. Using MRP and expandable graphite (EG) as co-flame retardants and HIPS asmatrix, HIPS/EG/MRP composites were obtained by melt compounding. The flameretardancy and flame retardant mechanism were studied in detail. The results indicatethat there exists very good synergistic flame retardant effect between MRP and EG.The as-prepared composites exhibit excellent flame retardancy and conductivity,which provide a new way for the development of high-performance HIPS composites.