Synthesis Of The Hybrids Of Organic-phosphonates With Inorganic Micro/nano Materials,and Their Applications In Epoxy Resin

As one of the most common thermoset polymers,epoxy resin（EP）exhibits exceptional adhesiveness,good mechanical properties and chemical resistance.Unfortunately,the intrinsic flammability restricts its applications in some fields.The halogen-containing flame retardants are undergoing the restriction due to the toxic gases release upon combustion.Thus,a variety of halogen-free flame retardants,such as metal hydroxides,phosphorous/nitrogenous compounds and some other compounds,are attracting great attention.However,the introduction of these compounds as sole flame retardants usually fails to achieve satisfactory flame retardancy,but also worsen the thermal or mechanical properties of EP.Thereby,it has become a top priority to improve the flame retardancy of EP and meanwhile to maintain its thermal and mechanical properties.The metal-organic phosphonates with intrinsic organic groups exhibit good compatibilities with polymer matrix and show great potential in flame retarding polymeric composites.In addition,many researches prove that some micro/nano fillers are capable of favoring the flame retardancy and mechanical reinforcement of polymeric composites.Hence,the synthesis of several metal-organic phosphonates,and their synergistic effects and mechanism with some micro/nano fillers in EP were studied in the dissertation.The major research contents are as follows:1.Four ethylenediamine tetra-methylene phosphonic acid（EDTMP）salts,i.e.EDTMP-aluminum（AETP）,EDTMP-zinc（ZETP）,EDTMP-tin（TETP）,and EDTMP-copper（CETP）,were synthesized and characterized by transmission electron microscopy（TEM）,Fourier transform infrared spectroscopy（FTIR）,X-ray diffraction（XRD）and thermogravimetric analysis（TG）.The EP/EDTMP salts composites were prepared and their mechanical performances,flame retardancy and thermal decomposition properties were thoroughly evaluated.At the loading of 5.0 wt%,the EP composite containing CETP（EP/CETP-5）passes UL-94 V-0 rating,the EP/TETP-5 and EP/ZETP-5 composites pass V-1 rating,and the EP/AETP-5 composite fails to pass any rating.Compared to the ones of pure EP,the peak heat release rate（p HRR）,total heat release（THR）and total smoke release（TSR）values of the EP/CETP-5 composite are decreased by 57.3%,33.3%and 48.4%,respectively.The TG test results demonstrate the improvement on the charring capacity of EP by the incorporation of AETP,ZETP,TETP or CETP.The experimental char residues of the EP/TETP-5 and EP/CETP-5composites decrease by 54.8%and 46.6%,respectively compared with their theoretical values.The mechanical tests results show that the EP/TETP-5 composite possesses increased tensile and impact strengths,whereas the EP/CETP-5 composite shows slightly decreased tensile and impact strengths,compared to pure EP.To sum up,TETP has good performance in improving the flame retardancy,maintaining the mechanical properties and thermal stabilities of EP,which is worthwhile fot further study.2.The nano-dimension carbon microspheres（CMS）were synthesized using glucose as raw material through hydrothermal reaction,and a botryoidal CMS/TETP hybrid（CMS@TETP）was fabricated via an in-situ method,and characterized by TEM,scanning electron microscope and energy dispersive X-ray spectra（SEM-EDS）,FTIR,XRD,X-ray photoelectron spectroscopy（XPS）and TG.The EP/CMS@TETP composites were prepared and their flame retardancy,mechanical properties and thermal degradation behaviors were studied.The combustion test results reveal that the EP composite containing 3.0 wt%CMS@TETP passes UL-94 V-1 rating with a LOI of27.0%（22.5%of pure EP）,and its p HRR and THR are respectively reduced by 59.1%and 47.0%in comparison with those of pure EP.However,the incorporation of CMS significantly improves the smoke generation of EP composites during combustion,and TETP makes up this shortage to some extent.The TG results provide evidence that CMS@TETP has good char-forming capacity in EP.The mechanical tests results show that the addition of 1.0 wt%CMS@TETP endows EP composite with an increase in tensile and impact strengths of 24.4%and 23.1%,respectively relative to the values of pure EP.3.The mesoporous silica（mSiO₂）was synthesized by the alkaline hydrolysis of tetraethoxysilane,and a hybrid flame retardant（mSiO₂@TETP）was fabricated by in-situ immobilizing TETP on the mSiO₂ surface,and characterized by TEM,SEM-EDS,N₂ adsorption-desorption isotherms,FTIR,XRD,XPS and TG.The EP/mSiO₂@TETP composites were prepared and their flame retardancy,mechanical and thermal degradation properties were investigated.At the same loading level（3.0 wt%）,mSiO₂@TETP shows flame retardancy in EP than either mSiO₂ or TETP.Remarkably,the EP composite containing 5.0 wt%mSiO₂@TETP succeeds to UL-94 V-0 rating,with a LOI value of 29.0%（23.5%of pure EP）,and the p HRR,THR,and TSR respectively decrease by 54.0%,50.0%and 51.1%in comparison with the values of pure EP.The TG and TG-FTIR results show that the addition of mSiO₂@TETP improves the charring capacity and restricts the thermal pyrolysis of EP composites.The differential scanning calorimeter（DSC）results show that the glass transition temperatures of EP/CMS@TETP composites are slightly increased in comparison to that of pure EP.The mechanical tests results show that the tensile strength and impact strength of EP composite containing 1.0 wt%mSiO₂@TETP increase by 20.5%and12.8%,respectively relative to those of pure EP.4.A novel organic phosphonic acid,i.e.N,N’-piperazine（bismethylene phosphonic acid）（PBA）was synthesized,and four PBA salts including PBA-aluminum（Al PB）,PBA-zinc（ZnPB）,PBA-tin（Sn PB）and PBA-copper（Cu PB）were synthesized and characterized by TEM,FTIR,XRD and TG.The EP/PBA salts composites were prepared and their flame retardancy was compared.It is found that,at the same dosage（3.0 wt%）,the EP composite containing Cu PB（EP/Cu PB-3）passes UL-94 V-0 grade,the EP/Sn PB-3 composite passes V-1 grade,and neither the EP/Al PB-3 nor EP/ZnPB-3 composites obtain any grade.Moreover,the p HRR,THR and TSR results of the EP/Cu PB-3 composite are respectively 43.5%,28.0%and 37.3%lower than those of pure EP,and the char residue after combustion increases from 10.2%to 26.3%.The TG and TG-FTIR results indecate that Cu PB reduces the maximum weight-loss rate and the thermal pyrolysis,and improves the char residue of EP.The mechanical properties results show that the tensile and impact strengths of EP/Cu PB-3 composite decrease by11.1%and 19.4%,respectively compared with those of pure EP.5.Layered PBA zinc（ZnPB）was immobilized on the surface of graphene oxide via an in-situ method,and then underwent a hydrothermal reduction reaction to obtain reduced graphene oxide/ZnPB hybrid（rGO@ZnPB）.The rGO@ZnPB was characterized by TEM,SEM-EDS,FTIR,XRD,XPS and TG.The EP/rGO@ZnPB composites were prepared and their flame retardancy,mechanical properties and thermal degradation properties were studied.It is found that rGO@ZnPB possesses better flame retardancy than rGO,ZnPB or their physical mixture in EP at the same loading（3.0 wt%）.The EP composite with 5.0 wt%rGO@ZnPB succeeds to UL-94 V-0 rating with a LOI value of 29.5%（23.5%of pure EP）,and the p HRR,THR and TSR values are decreased by 38.7%,30.5%and 33.7%,respectively with respect to these values of pure EP.The TG and TG-FTIR results show that the addition of rGO@ZnPB improves the char-forming capacities of EP,and inhibits its thermal pyrolysis.The DSC results manifest that the glass transition temperatures of EP/rGO@ZnPB composites are improved to some extent.The mechanical test results show that the tensile strength and impact strength of the EP composite containing 1.0 wt%rGO@ZnPB are 20.9%and 15.1%higher than the ones of pure EP.6.The mSiO₂ and PBA zirconium（Zr PB）hybrid（mSiO₂@Zr PB）was prepared and characterized by TEM,N₂ adsorption-desorption isotherms,FTIR,XRD and TG.The synergistic effects between mSiO₂@Zr PB and 10-（2,5-dihydroxyphenyl）-10H-9-oxa-10-phosphaphenanthrene-10-oxide（DOPO-HQ）on the curing behavior,flame retardancy,mechanical properties and thermal decomposition properties of epoxy/cyanate copolymer（EPCE）were studied.The real-time FTIR results show that the incorporations of DOPO-HQ and/or mSiO₂@Zr PB affect the curing reactions of EP and CE,and promote the formation of more triazine-ring network structures.The combustion test results conform that DOPO-HQ and mSiO₂@Zr PB display synergistic flame retardancy in EPCE.The EPCE composite containing 8.0 wt%DOPO-HQ and2.0 wt%mSiO₂@Zr PB passes UL-94 V-0 rating with the highest LOI of 30.5%,and exhibits the lowest THR（～26.8%decreased compared to that of pure EPCE）.Furthermore,the addition of mSiO₂@Zr PB inhibits the smoke emission of EPCE composites caused by DOPO-HQ.Additionally,the incorporation of the mixture of DOPO-HQ and mSiO₂@Zr PB imparts EPCE with improved charring capacity during the combustion and pyrolysis,improved thermal anti-oxidation degradation capacity,and increased glass transition temperatures as well.The mechanical test results show that the tensile and impact strengths of the EPCE composite containing 9.0 wt%DOPO-HQ and 1.0 wt%mSiO₂@Zr PB are respectively 19.1%and 18.9%increased than that of pure EPCE.The dielectric test results show that the EPCE composites containing DOPO-HQ and/or mSiO₂@Zr PB retain low dielectric constant and dielectric loss tangent.