| The additive flame retardant is widely utilized to improve the flame retardancy of the polymer.The existing additive flame retardant has significant flame retardant effect,but there are still some practical problems,such as excessive addition,mechanical strength reduction,environment pollution.Therefore,research in functional flame retardant additives and the synthesis of synergistic flame retardants with specific functions has received grate attention.9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO)is a phosphorus-containing compound with biphenyl structure,high thermal stability,good oxidation resistance and hydrophobicity,which is considered as a high-efficiency flame retardant.The active hydrogen in the DOPO has the possibility to react with the aldehyde group.In addition,DOPO structure contains P-H bond,which is also highly active for C=C and C=N.Based on DOPO,four nitrogen-phosphorus flame retardants were designed and synthesized,the effects of thermal stability,flame retardancy and mechanical properties of modified epoxy resin were studied,and their flame retardancy mechanism was preliminarily discussed,which provided a new reference and thought for the research and development of halogen-free flame retardant epoxy resin composites.The main research contents of this thesis are as follows:Firstly,a novel flame retardant hsaltryptamine phosphaphenanthrene(HTD)was successfully synthesized and characterized by infrared spectrometry(FT-IR)and nuclear magnetic resonance(NMR).HTD was used to improve flame retardancy of epoxy resin(EP).The transmittance and mechanical properties of EP/HTD thermosets had been tested.EP/HTD thermosets had good transparence,for example,EP/2%HTD has a transmittance of 93% in the wavelength of 750nm-800 nm.With the decrease of wavelength,EP/HTD became less transparent.When the wavelength is about 450 nm,EP/HTD thermosets had poor light transmittance.The EP/4%HTD thermoset Passed a UL-94 V-1 rating and had limited oxygen index(LOI)value of 29.2%.Compared with neat EP,the release of heat and smoke decreased significantly due to the gaseous phase and condensed-phase flame-retardant mechanism of HTD.The char residue after cone calorimeter test were analyzed and the results showed that the char residue of EP/8%HTD thermoset exhibited homogeneously cross-linked char layer,which acted as a good barrier for the release of heat and oxygen.EP/HTD thermoset possessed high transparency and good mechanical properties.Secondly,A novel flame retardant poly(piperazine phosphaphenanthrene)(DOPMPA)was synthesized successfully via two step reactions using DOPO and piperazine as reactants and characterized by infrared spectrometry(FT-IR),nuclear magnetic resonance(NMR)and gel permeation chromatography(GPC).In co MParison to neat epoxy resin,tensile strength,flexural strength and izod unnotched impact strength of epoxy resin with 13% loading of DOPMPA was decreased by 26.8%,29.5% and 23.9%,respectively.The DOPMPA was used to enhance flame retardancy of epoxy resin(EP).When the addition content of DOPMPA was 13 wt%,the EP/DOPMPA sample Passed a UL-94 V-0 rating and possessed a high limited oxygen index(LOI)value of 34%.Besides,the release of heat and smoke for EP/DOPMPA samples decreased significantly co MPared with neat EP.Moreover,the reduction of average effective heat of combustion(av-EHC)value with the increased addition of DOPMPA confirmed that DOPMPA had a flame-inhibition activity in gashouse phase.The analysis of the char residues after cone calorimeter test exhibited that DOPMPA promoted the formation of intumescent and co MPact char layer.Furthermore,the pyrolysis analysis of DOPMPA were investigated by pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS),which illustrated that DOPMPA decomposed into many fragments with quenching effect to terminate chain reaction of combustion.Thirdly,a novel flame retardant hsalbenzoguanamine phosphaphenanthrene(HDPD)was synthesized based on benzoguanamine and DOPO.The structure of HDPD was successfully characterized by infrared spectrometry(FT-IR)and nuclear magnetic resonance(NMR).HDPD was used to improve properties of epoxy resin.The transmittance and mechanical properties of EP/HDPD thermosets had been tested.EP/HTD thermosets had good trans Parence,for example,the transmittance of EP/6%HDPD thermoset at 800 nm was nearly 90% of the control group.in the wavelength of 750nm-800 nm.With the decrease of wavelength,EP/HDPD became less transparent.When the wavelength is about 450 nm,EP/HDPD thermosets had poor light transmittance.In comparison to neat epoxy resin,tensile strength,flexural strength and izod unnotched impact strength of epoxy resin with 6% loading of HDPD was decreased 79MPa、77MPa和 22 MPa,respectively.HDPD was used to modify the properties of epoxy resin(EP)and the flame retardancy of EP/HDPD thermosets was dramatically improved.LOI and UL-94 results showed the EP with 6 wt% HDPD Passed a UL-94 V-0 rating with a LOI value of 33.5%.The data of the CC test showed the release of heat and smoke from EP/6%HDPD thermoset was restrained significantly.In addition,EP/6% HDPD thermoset possessed perfect transmittance and mechanical properties.In order to investigate the flame-retardant mechanism of EP/HDPD thermoset,XPS,FTIR,SEM,Raman and Py-GC/MS tests were performed,and the results demonstrated that HDPD played a positive effect in both condensed-phase and gaseous-phase.Finally,a novel flame retardant phthalaldehydepyrazole phosphaphenanthrene(PPMD)was synthesized based on 5-amino-3-methyl-1-phenylpyrazole and DOPO.The structure of PPMD was successfully characterized by FT-IR and nuclear NMR.PPMD was used to improve properties of epoxy resin.The transmittance and mechanical properties of EP/PPMD thermosets had been tested.EP/ PPMD thermosets had good transparence,for example,the transmittance of EP/5% PPMD thermoset at 800 nm was nearly 90% of the control group in the wavelength of 750nm-800 nm.With the decrease of wavelength,EP/ PPMD became less transparent.When the wavelength is about 450 nm,EP/PPMD thermosets had poor light transmittance.In comparison to neat epoxy resin,tensile strength,flexural strength and izod unnotched impact strength of epoxy resin with 5% loading of PPMD was decreased 81 MPa,77MPa and 22 MPa,respectively.PPMD was used to modify the properties of epoxy resin(EP)and the flame retardancy of EP/PPMD thermosets was dramatically improved.LOI and UL-94 results showed the EP with 5 wt% PPMD Passed a UL-94 V-0 rating with a LOI value of 31.7%.The data of the CC test showed the release of heat and smoke from EP/5% PPMD thermoset was restrained significantly.In order to investigate the flame-retardant mechanism of EP/PPMD thermoset,XPS,FTIR,SEM,Raman and Py-GC/MS tests were performed,and the results demonstrated that PPMD played a positive effect in both condensed-phase and gaseous-phase. |
PDF Full Text Request