Synthesis Of Multi-elements Synergistic Flame Retardant And Its Application In Epoxy Resin

Epoxy resin has been widely used in many fields.However,the worldwide market for common epoxy resins has become almost saturated,and the high value-added epoxy resins have attracted great research interest in developed countries.Therefore,it’s of great significance to develop flame retardant epoxy resins which possess good comprehensive performance.In this paper,a reactive synergistic flame retardant containing P and N(ADDPP-OH)and an organic-inorganic hybrid multi-element containing synergistic flame retardant(SiO2@TAMPS)were synthesized from tetrakis(hydroxymethyl)phosphonium sulfate(THPS),which is a kind of cheap and environmental industrial raw materials and easy to react with amines.The structure of ADDPP-OH and SiO2@TAMPS were characterized by a variety of techniques.The modified epoxy resins were prepared and investigated by morphological characterization,thermal stability analysis,flame retardancy test,char layer analysis and mechanical properties test.The main achievements of our work are shown as follows:1.ADDPP-OH,which possesses chemical reactivity and good hydrolysis resistance due to its phenolic hydroxyl and P-C-N bond containing azaphosphoriane,was synthesized from THPS,p-aminophenol and triethylamine through Mannich reaction.The yield was 73.5%.An organic-inorganic hybrid multi-element containing synergistic flame retardant SiO2@TAMPS was synthesized from THPS,p-phenylenediamine and SiO2,and its yield was 70%.It not only improved the compatibility between SiO2 and epoxy resin,but also achieved synergistic flame retardancy in nanoscale.The two synthetic routes were convenient and mild for industrial manufacture.Their structures were characterized by FT-TR,NMR,SEM,TEM,DLS,XRD and TGA.The results showed that the target products were successfully synthesized.2.ADDPP-OH was used as a co-curing agent and flame-retarding agent for epoxy resins.Compared with pure EP,the cured ADDPP-OH/EP resins had better thermal stability,lower maximum thermal decomposition rate and higher char residues.Also,the LOI value of cured resins was higher than 32%and the UL-94 rating reached V-0 grade when the addictive amount of ADDPP-OH was 10 wt%.SEM characterization indicated that its char residue had a compact and continual morphology in outer layer,intumescent and multi-porous inner layer,which can hinder the transfer of heat and oxygen into underlying polymer matrix.Moreover,the cross-linked phosphorocarbonaceous and phosphorooxidative char layers containing P-O-Ph and P-O-C formed during combustion due to the incorporation of ADDPP-OH.It showed that both storage modulus and calculated crosslinking density of cured ADDPP-OH/EP resins increased at first and then decreased again.It could be explained that the hydroxyl groups in ADDPP-OH could react with epoxy groups of epoxy resins,thus leading to a increased crosslink density.While ADDPP-OH tended to aggregate at a higher loading,thus caused the decrease in crosslink density.3.Tg,Tmax and char residues of the cured SiO2@TAMPS/EP resins were higher than those of EP-SiO2 resins,and they increased as the amount of SiO2@TAMPS increased,which indicated that SiO2@TAMPS could improve thermal stability of epoxy resins.Also,the LOI value of cured resin was higher than 30.3%and the UL-94 rating reached V-0 when the addictive amount of SiO2@TAMPS was 2 wt%.The char layer analysis showed that it had intumescent and vesicle structure in inner layer,which contained Si-O-Si structure.Raman spectroscopy further indicated that SiO2@TAMPS increased the degree of graphitization of char residues,that is,it was more stable at high temperature.The data of mechanical properties showed that the introduction of SiO2 to epoxy resin decreased its strength and toughness,while SiO2@TAMPS enhanced its interaction with epoxy resins,thus improving the mechanical properties of cured resins.