Synthesis Of Nitrogen-Sulfur-Silicone Flame Retardant And Its Application In Polycarbonate

Polycarbonate(PC)is widely used in various fields,such as electronic,electrical,aerospace,construction,automotive,household,etc,due to its excellent comprehensive performance.Although PC has certain flame retardant properties,the serious dripping phenomenon in the PC burning process makes it unable to meet the requirements of the more stringent flame retardant fields.Therefore,the current development of halogen-free,high-efficiency,low-smoke,environmentally friendly and excellent comprehensive performance flame retardants can effectively expand the scope of PC applications.Triazine compounds are important flame retardants for polymer materials because of their good carbon-forming properties.In this paper,a triazine flame retardant containing three flame retardant elements of nitride,sulfur and silicon was synthesized based on cyanuric chloride and applied to PC.The main research contents are as follows:(1)The flame retardant 2,2'-(1,1,3,3-tetramethyldisiloxane-1,3-bis(3-aminopropyl))-bis(4-(potassium sulfamate)-6-(4-hydroxyphenyl)amino-1,3,5-triazine)(KTS)was synthesized by cyanuric chloride,aminoethanesulfonic acid,p-aminophenol,1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane as raw materials,and several influence factors in the process of the reaction are discussed.The structures of KTS was characterized by high resolution mass spectrometry(ESI-MS),nuclear magnetic resonance spectroscopy(NMR)and fourier transform infrared spectroscopy(FTIR).The thermogravimetric analysis(TGA)was used to test the thermal stability of KTS.The results showed that the initial decomposition temperatures of KTS under nitrogen and air atmosphere were 337.0?and315.2?,respectively,showing good thermal stability and meeting the processing requirements of PC.(2)The flame retardancy of the composites were studied by limit oxygen index(LOI)and horizontal vertical combustion(UL 94),and the mechanical properties were investigated.The studies showed that when the addition of KTS was 0.5 wt.%,the LOI value of PC/KTS composites was 34.6%,passed the UL 94 V-0,and the tensile and bending strength did not change significantly compared with the substrate,but the impact strength decreased from14.63 kJ/m~2 to 4.43kJ/m~2.The LOI value of PC/0.1wt.%KTS/0.1wt.%PTFE composites prepared by adding anti-dripping agent polytetrafluoroethylene(PTFE)was 34.4%,passed UL 94 V-0,and the toughness of PC material was significantly improved by adding PTFE.(3)The combustion and thermal degradation behavior of the composite were analyzed by cone calorimetry(CONE)and thermogravimetric analysis(TGA).The result showed the ignition time(TTI)of PC/KTS composites was shortened by adding KTS,When KTS added0.5 wt.%,the pk-HRR and pk-SPR were decreased by 41%and 33%,respectively.At the same time,the addition of KTS advances the initial decomposition temperature of the composite,promotes PC to form a carbon layer with higher thermal stability,and reduces the maximum thermal decomposition rate.The morphology and structure of residual carbon were analyzed by scanning electron microscopy-X-ray energy spectroscopy(SEM-EDS)and Raman spectroscopy(LRS),and it was found that PC/KTS composites formed dense and continuous carbon layer with sponge-like microporous structure in the combustion process,with higher graphitization degree compared with pure PC.The kinetic results showed that as the conversion rate increases,the apparent activation energy of thermal degradation of PC/KTS composites decreases first and then increases compared with pure PC.KTS is a highly efficient flame retardant with good thermal stability,while playing a role of flame retardant in the gas phase and condensed phase,it not only makes PC/KTS composites have anti-drip,anti-smoke and anti-toxicity,but also improves the compactness and thermal stability of the carbon layer,prevents the flame from spreading.