Study On Thermal Polymerization Modification Of The Medium Temperature Coal-tar Pitchand Its Modification Mechanism

This paper mainly studies on thermal polymerization modification of the mediumtemperature coal-tar pitches and its modification mechanism. The coal-tar pitcheswere modified with anthracite additives, epoxy resin additives or epoxyresin+anthracite additives with thermal polymerization process by controllingmodification time or modification temperature.In order to study the impact of the modification time, we adopted thermalpolymerization modification to modify the parent coal-tar pitch which named CTP-01.Modification technological parameters are as follows.The N₂flow is50mL/min. Themodification temperature is200centigrade, and the modification time is2to5hours.The results show that the fixed carbon content of modified coal-tar pitch namedA-2was increased by51.62%to56.55%. The softening point was increased from93.6degrees Celsius to101.5degrees Celsius. The content of βcomponents was increased.Thus we conclude a reasonable modification time for3hours.We use thermal polymerization modification with anthracite modifier to modifythe parent coal-tar pitch which named CTP-01, and then study the effect of differentamount of modifier. Modification technological parameters are as follows.The N₂flow is50mL/min. The modification time is3hours. The modification temperature is200centigrade.The modification additives are anthracite which the dose is0wt%、1wt%、2wt%or3wt%.The results show thatthe fixed carbon content of modifiedcoal-tar pitch which named B-1was increased by51.62%to59.96%. The softeningpoint was increased from93.6degrees Celsius to106.1degrees Celsius. The contentof βcomponents was increased by4.97%. Thus we conclude a reasonable modificationamount of anthracite modifier for1wt%.We use thermal polymerization modification with1wt%anthracite additives tomodify the parent coal-tar pitch which named CTP-01, and then research the effect ofdifferent modification temperature.Modification technological parameters are asfollows.The N₂flow is50mL/min. The modification time is3hours. The dose of theanthracite modifier is1wt%. The modification temperature is200,250or300centigrade.The results show that the pyrolysis and associated poly-condensationreaction exacerbated in the process of modification with the improvement ofmodification temperature.The fixed carbon content of modified coal-tar pitch which named B-5was increased by51.62%to61.51%. The softening point was increasedfrom93.6degrees Celsius to108.0degrees Celsius. The content of β components wasincreased by5.30%. The weightlessness rate decreased from65.28%to61.13%.The parent coal-tar pitch was modified with3wt%of epoxy resin additives or3wt%epoxy resin+1wt%anthracite additives by thermal polymerizationmodification.Modification technological parameters are as follows.The N₂flow is50mL/min. The modification time is3hours. The modification temperature is300centigrade.The dose of the modifier is3wt%epoxy resinor3wt%epoxy resin+1wt%anthracite.The results show that EηC-2>EηC-1>EηCTP-01.The fixed carbon contentof C-2reached64.20%, and it’s volatile content fell to58.04%, beta resin contentreached19.12%.The weightlessness rate decreased from65.28%to60.15%.Thermalanalysis of the quinolone insoluble component in coal-tar pitch which namedCTP-01、 C-1、 C-2was taken.The results show that the pyrolysis andpoly-condensation characteristics of the components in coal-tar pitches changed. Thetemperature of fastest weightlessness rate rose, the pyrolysis and poly-condensationcharacteristics of the components in coal-tar pitches before and after modificationchange gentlely.The changes in organizational structure of the coal-tar pitches before and afterthermal polymerization modification was researched by polarized micr oscopy,Fouriertransform infrared spectroscopy （FT-IR）,gas chromatography-mass spectrometermethod （GC-MS） and scanning electron microscopy （SEM）.The results show that thespread of components in coal-tar pitches changed, and the mesophase ball of themodified coal-tar pitch increased.With mono aromatic reduced and dicyclic aromaticincreased, the aromaticity of the modified coal-tar pitch increased significantly.Meanwhile, the relative abundance of polycyclic aromatic hydrocarbons wasenhanced differently.Meanwhile, the modified mechanism was studied according toGC-MS analysis combined with the FT-IR analysis.The microstructure of coal-tarpitch’s carbonized product includes isotropic, mosaic, streamlined and regional-type,etc. The toluene insoluble component has lamellar microstructure. The quinolineinsoluble of coal-tar pitch has isotropic morphologyof reunion particles.And theaverage particle size is about0.5μm.