Synthesis And Characterization Of Fluorenyl Epoxy Resin And Curing Agent

9,9-bis(4-hydroxyphenyl)-fluorene(BHPF) is a type of bisphenol fluorenecompounds with Cardo skeleton which is obtained by the condensation offluorenone with phenol in the presence of at least one acidic condensation agent.9,9-bis(4-aminophenyl)-fluorene(BAF) is a diamine compound used as curingagents of epoxy resins.BHPF can be used as monomer or modifier for thepreparation of high performance polycondensation products such as epoxy resins,polycarbonates,polyesters and polyethers,due to the unique properties of Cardorings such as thermal stability.The polymers obtained from bisphenol fluorenehave been found to exhibit desirable complex characteristics such as thermalstability,high transparency,high-refractive index and insulation,which makesthem useful in the applications in aerospace,electro-optics,electronic,automotiveand related industries.Relevant examples included but are not limited to:aircraftstructure articles,flame-retardant laminates,heat-resistant adhesives,high-temperature coatings,photoelectric conductors,fibre optics and films,et al.BHPF and BAF were synthesized from fluorenone and phenol or amine in thepresence of acidic catalyst,and the major factors affecting the reaction wereinvestigated.The chemical structures of products were confirmed by FTIR,NMR,MS and elemental analysis.The results showed that solid acid catalyst had highcatalytic activity and was easy to recover,and the process of waste acidneutralization was reduced.The mass percentage and yield of BHPF reached99.5% and about 85% respectively under optimal process conditions that themolar ratio of phenol to fluorenone was 8 to 1,the mass percentage of catalystwas 14% of the total reactants,reaction temperature was 105℃and reaction time was 12 h.The melting point(m.p.) of BHPF was 222-223℃.The yield and m.p.of BMPF and BDMPF were 67%,76.8%,217-219℃,289-291℃,respectively.The synthesis reaction of BHPF proceeds via nucleophilic addition-eliminatoin.BMPF was synthesized from 9,9-dichloro-fluorene in the presence ofmethanesulfonic acid with the dichloro-fluorene and o-cresol molar ratio from 1to 3.4 below 30℃.The yield of BMPF with m.p.of 218-219℃was 67%.Theprocess has been proved a novel method for the synthesis of BHPF with mildreaction conditions and short reaction time.Synthesis method of BAF,BMAF,BNMAF,and BDMAF is the same as thatof BHPF.A stream of nitrogen was introduced and the mixture includingfluorenone and amine,such as aniline,ortho-toluidine,N-methylaniline,dimethylaniline,was heated at 150-175℃for 12-16 h with vigorous stirring.Theyield of fluorenyl diamine was about 70%,and the m.p.was 236-237℃,230-232℃,205-207℃,and 120-121℃,respectively.Fluorene-containing epoxy resins,diglycidyl ether of 9,9-bis(4-hydroxy-phenyl)-fluorene(DGEBF),diglycidyl ether of 9,9-bis(3-methyl-4-hydroxy-phenyl)-fluorene(DGEMBF),and diglycidyl ether of 9,9-bis(2,6-dimethyl-4-hydroxyphenyl)-fluorene(DGEDMBF),was synthesized from BHPF,BMPF,or BDMPF and epichlorohydrin by the method reported previously.Epoxy valueof DGEBF,DGEMBF,and DGEDMBF was 0.405,0.368,and 0.334 eq/100g,respectively.The curing kinetics and curing craft of fluorenyl diamines with differentepoxy resins including DGEBF,DGEMBF,cycloaliphatic epoxy resin(TDE-85)and diglycidyl ether of bisphenol A(DGEBA),was investigated usingnon-isothermal differential scanning calorimetry(DSC),and determined byKissinger,Ozawa and Crane methods.The activation energy calculated by Kissinger method was less than that by Ozawa method.The reaction order wasless than 1.It showed that complex reations occurred in the above-mentionedsystem.The relationship of structure and performance about fluorenyl epoxy resinsand fluorenyl diamines was investigated by DMA and TGA.DGEBF have astructure in which a bulky fluorene unit protrudes vertically from the polymermain chain.This chemical structure of four phenyl rings connected to aquaternary carbon leads to severe rotational hindrance of the phenyl groups.Therefore,the stiff,bulky cardo moiety likely arise from the higher rigidity offluorene skeleton in the chain backbone,which would restrain the internalrotations and thermal motion of polymer segments.Heat resistance and thermaldecomposition activation energy of the cured polymers can be elevated drasticallyby introducing some rigid groups into the backbone of epoxy monomer.Thehydrophobic fluorene moieties might be responsible for the lower moistureabsorption for fluorenyl diamines.The average volume of fluorene ring isdeduced to be larger than those of methylene or cyclohexyl groups,and it mightcause a reduced crosslink density in the network of cured polymers to produceless hydroxyl groups,and finally leads to an improved hydrophobicity of thesystem.In addition,more contents of phenyl group than DDS,DDM,andanhydride decrease the polarity of cured polymers,and inhibit water to invade.Fluorenyl epoxy resins is compatible with current epoxy resins.The thermalstability and moisture resistance of commercial epoxy resins were modifiedthrough blending.The blend resin made from DGEBF,DGEBA,and TDE-85 wascured by BAF.The storage modulus,glass transition temperature and wateruptake(boiling water,72h) of cured resins were 2.65 GPa,210℃,and 2.28%,respectively.The polymer can be used for a long time at 200℃.Toughening agent,such as PU,CTBN,PES,et al,can improve toughness of cured resins.However,PU and CTBN can decrease the heat resistance of cured resins exceptPES.