GF-KH550 with amino-rich surface was firstly obtained from amination treatment of cut glass fiber(GF)by 3-aminopropyl triethoxysilane(KH550).Hyperbranched polyphosphamide interfacial flame-retardant glass fiber(GF@HBPN)was then synthesized by in-situ polymerization on the surface of GF-KH550 using triethylamine as acid binding agent as well as catalyst,POCl3 and 4,4-diaminodiphenylmethane as monomers,and characterized by FTIR,XPS,SEM and TGA.Finally,polylactic acid(PLA)composites(GF-KH550/PLA,GF@HBPN/PLA and APP/GF@HBPN/PLA)were prepared from GF-KH550,GF@HBPN or mixture of GF@HBPN and ammonium polyphosphate(APP),and further tested for analyses on their thermal stability,mechanics and flame-retardant properties.The results showed that compared with that of PLA,GF-KH550/PLA displayed obviously improved tensile strength but worsened combustion performance due to the"candle wick effect"of GF,while GF@HBPN/PLA exhibited increment both in tensile strength as well as combustion performance(UL-94 V-2).The improvement in combustion performance of GF@HBPN/PLA was attributed to the inhibition of"candle wick effect"by the interfacial carbon residue formed on GF surface,however,this improvement was not enough to achieve the ideal flame-retardant effect.The 10%APP/30%GF@HBPN/PLA composites prepared with 10%(mass fraotion)APP and 30%(mass fraction)GF@HBPN exhibited excellent fire safety performance with the limit oxygen index of 26.8%±0.2%and the vertical combustion grade of UL-94 V-0.Moreover,the heat release rate peak value,total heat release rate and average effective heat of combustion rate decreased by 31.39%,23.57%and 18.80%,respectively,compared with those of PLA.
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