Preparation,modification Of Plant-Based PCM And Study On Its Flame Retardant Synergism For Epoxy Resin By Experiment And Simulation

With the gradual improvement of the global laws,regulations and the industry standards on flame retardacy of materials,it is necessary to consider both reducing fire hazard and the impact on the environment when flame retardants are applied.Therefore,the development of efficient green flame retardant technology has become a trend in this filed.Synergistic effect produced by combining a small amount of synergist with flame retardants in composites with improved flame retardance efficiency is one of the most potential and hottest research spot.Meanwhile,as a result of the development of computer technology and theoretical chemistry,simulation has been attracting more and more attention on develop and research of new materials.In this thesis,plant-based porous carbon materials?PCM?with the large specific surface area and different surface activities have been prepared by KOH chemical activation method.Besides,PCM and modified PCM?MPCM?were combined with ammonium polyphosphate?APP?or aluminium diethylphosphinate?AlPi?as synergist to improve flame retardancy of epoxy resin?EP?.And the synergistic flame retardant mechanism of PCM and MPCM were studied by the experimental method combined with simulation method.?1?The optimized preparation of PCM.PCM6 was prepared from bamboo by controlling the porogen ratio,reaction temperature and activation temperature.The characteristic of PCM6 was that the specific surface area was 2063 m2/g,particle size was about 1⁵?m,there were C-O-,C=O and COO-active groups on the surface besides the graphite carbon.?2?The study on synergistic flame retardant mechanism of PCM6 and APP in EP composites.The combustion performances of PCM6 with APP flame retardant EP were studied using the limit oxygen index?LOI?,UL 94 vertical burning test and cone calorimeter?Cone?.The results indicated that when 3.1 wt.%of APP and 0.8 wt.%of PCM6 were added into EP,the LOI of EP/3.1APP/0.8PCM6 reached 27.3%,heat and smoke release was decreased,the time to ignition was prolonged,indicating PCM6 showed a good synergistic flame retardant effect.The thermal decomposition behaviour and synergistic flame retardant mechanism were studied using thermo-gravimetric analysis?TGA?,thermogravimetric analysis coupled with Fourier transform infrared spectrometry?TG-FTIR?or mass spectrometry?TG-MS?,Fourier transform infrared spectrometry?FTIR?,confocal Raman spectra?CRS?and X-ray photoelectron spectroscopy?XPS?.The results showed that PCM6 and APP increased the amount of char residual and mainly exhibited synergistic effect in the condensed phase by promoting the formation of conjugated aromatic rings.Molecular dynamics?MD?simulation indicated that compared with PCM7?O/C=0.05?,PCM6?O/C=0.39?showed a stronger interaction with APP and EP,revealing that the surface active groups on PCM are advantageous to the synergistic flame retardant effect from molecular level.With the aid of dissipative particle dynamics?DPD?simulation,the flame retardant effects were analyzed by the difference between EP/3.1APP/0.8PCM6 and EP/3.1APP/0.8PCM7 on the mesoscopic morpholog y.?3?The preparation of modified PCM and the study on its synergistic flame retardant mechanism with APP in EP composites.Surface modified PCM6?M6PCM?was obtained by treating PCM6 with silane coupling agent and boric acid,leading to the surface was loaded with Si-B compounds and improved thermal stability was achieved.Compared with EP/6.2APP/1.6PCM6,the LOI of EP/6.2APP/1.6M6PCM increased by 1.5%,heat and smoke release was further decreased.Due to the stable char formed by silicon boron ceramic precursor at high temperatures,the synergistic flame retardant effect of M6PCM and APP in EP was improved.The synergistic mechanism of M6PCM and APP in EP showed that M6PCM accelerated the NH₃ and H₂O release from APP and the polyphosphoric acid formation.Meanwhile,silicon boron ceramic precursors promoted cross linking and char formation of EP,improving the char formation.MD simulations indicated that although M6PCM showed larger steric hindrance than PCM6,hydrogen bonds made the binding energy of EP/6.2APP/1.6M6PCM increased,therefore EP/6.2APP/1.6M6PCM showed a stronger intermolecular interaction.The reasons for the improvement of EP/6.2APP/1.6M6PCM flame retardant performance were established from molecular scale.DPD simulation indicated M6PCM was more uniformly dispersed with APP in EP matrix,which resulting an improved flame retardant performance.?4?Study on surface characteristic and morphology of carbon materials on combustion and thermal decomposition of flame retardant EP.The prepared plant-based PCM as well as purchased carbon materials were respectively used in flame retardant EP with APP to compare their combustion and thermal decomposition properties.The results indicated that granular plant-based PCM with larger specific surface area and higher O/C ratio showed the same flame retardancy effect with tubular CNTs.Although the microstructure of carbon material was the main factor influencing the combustion performance of EP composite,increasing of the specific surface area and the number of surface active groups of carbon materials also could help increase the amount,improve the graphitization and thermal stability of the char residue.?5?Study on the synergistic flame retardant mechanism of PCM6 and AlPi in flame retardant EP composites.The combustion performance indicated that AlPi combined with PCM6 showed good flame retardant property,with an increment of 18%in LOI,significantly decreased heat release compared with EP.The synergistic flame retardant mechanism of PCM6 and AlPi in EP showed that PCM6 catalyzed the decomposition of AlPi to release diethylphosphinic acid to capture free radicals and mainly showed synergistic effects in the gas phase.The MD simulations indicated that due to the effect of hydrogen bonding,the molecular interaction and compatibility of PCM6,AlPi and EP were increased,thus the flame retardant properties of composites improved.Besides,the mesoscopic morphology simulated by DPD further explained the binding energy enhancement effect on the flame retardant properties of EP/4.4AlPi/3PCM6.