Study On Thermal Stability And Flame Retardant Properties Of Nano-Sb₂O₃/BPS-PBT Composites

Polybutylene terephthalate?PBT?is one of the world's five general-purpose plastics.It has excellent mechanical properties,corrosion resistance,electrical properties,etc.It is widely used in electronics,automotive,machinery and other industries.PBT is mainly composed of C,H and O elements.It has poor flame retardant properties.It is easy to produce droplets during combustion and ignite surrounding combustibles,which brings great safety hazards.So,it is necessary to modify the flame retardant of PBT.In the flame retardant modification of PBT,the flame retardant with environmental and high efficiency should be selected to improve the flame retardant performance of PBT materials.Meanwhile it's important to ensure that the excellent properties of PBT matrix are not affected.Nanoparticles have a unique nano-effect and have an excellent improvement in the flame retardant efficiency of polymer materials.In this paper,nano-Sb₂O₃,micro-Sb₂O₃ and brominated polystyrene?BPS?were selected as flame retardants.The materials were uniformly mixed by high-energy ball milling and melt extruding.The injection molding method is used to make Sb₂O₃/BPS-PBT composite splines with different ratios of ingredients.Through the tests of combustion performance test,heat stability test,mechanical property test,etc.,the best ratio of PBT flame retardant and tensile properties was found,and the flame retardant mechanism of Sb₂O₃ and BPS was explored.The composite materials were compared to analyze the different flame retardant effects of nano-Sb₂O₃ and micro-Sb₂O₃,and the thermal decomposition process of nano-Sb₂O₃/BPS-PBT composites was analyzed by thermal decomposition kinetics to further study the flame retardant mechanism of the nano-Sb₂O₃/BPS-PBT composite.The main results are as follows:?1?Nano-Sb₂O₃ powder was prepared and modified.The nano-Sb₂O₃/BPS-PBT composites with different ratios were prepared,and the prepared samples were tested by limiting oxygen index test?LOI?and vertical burning test?UL94?.It was found that when the content of BPS was 10wt.%nano-Sb₂O₃,the PBT-based composites had a significant improvement.When the content of BPS is 10wt.%and the content of nano-Sb₂O₃ is 5wt.%,the LOI and UL94 of PBT-based composites are 28.3%and V-0,respectively,achieving flame retardant.And the mechanical properties are superior to pure PBT material.?2?Making deep analysis of nano-Sb₂O₃/BPS-PBT composites containing 10wt.%BPS,it's found that nano-Sb₂O₃ reduced the decomposition temperature of PBT-based composites,the heat release rate slowed down and the heat release amount was greatly reduced.And this effect was enhanced with the increase of nano-Sb₂O₃ content.Nano-Sb₂O₃ has a positive effect on the char formation of PBT materials.As the content of nano-Sb₂O₃ increased,the carbon layer formed was denser and the quality of residual substances was higher.?3?Comparing the different flame retardant effects of nano-Sb₂O₃ and micro-Sb₂O₃ on PBT,it was found that the effect of nano-Sb₂O₃ in reducing the heat release of PBT material was much larger than that of micro-Sb₂O₃ in the PBT-based composite.The total heat release of the micro-Sb₂O₃/BPS-PBT composites was more than 4 times that of the nano-Sb₂O₃/BPS-PBT composites,and the total smoke release of the micro-Sb₂O₃/BPS-PBT composites was more than 1.7 times that of the nano-Sb₂O₃/BPS-PBT composites.The carbon layer formed by the nano-Sb₂O₃/BPS-PBT composites was also denser than the carbon layer of the micro-Sb₂O₃/BPS-PBT composites.?4?The thermal decomposition kinetics of PBT and PBT flame retardant composites were studied by non-isothermal thermogravimetry.The kinetic parameters of PBT and PBT flame retardant composites were calculated by Kissinger method,Flynn-Wall-Ozawa method and Friedman method.The activation energy of PBT flame retardant composites during decomposition was higher than that of pure PBT materials.PBT flame retardant composites required more energy during thermal degradation.Nano-Sb₂O₃ and BPS have little change in the thermal degradation process of PBT.The thermal degradation process of PBT and PBT flame retardant composites can be simulated by Avarami-Erofeyev model?A1?.